PHOSPHORUS AND POTASSIUM CONTENT

OF COMMONLY CONSUMED

MEAT, POULTRY AND FISH PRODUCTS

IN PATIENTS WITH CHRONIC KIDNEY DISEASE

by

Arti Sharma Parpia, RD

A thesis submitted in conformity with the requirements

for the degree of Master of Science

Graduate Department of Nutritional Sciences

University of Toronto

© Copyright by Arti Sharma Parpia (2015)

ii

PHOSPHORUS AND POTASSIUM CONTENT OF COMMONLY

CONSUMED MEAT, POULTRY AND FISH PRODUCTS

IN PATIENTS WITH CHRONIC KIDNEY DISEASE

Arti Sharma Parpia

Master of Science

Department of Nutritional Sciences

University of Toronto

2015

ABSTRACT

Patients with chronic kidney disease (CKD) are advised to limit their intake of phosphorus and

potassium, yet there is uncertainty concerning the actual content of these minerals in the

Canadian food supply. In order to gain insight into the contribution of food additives to

phosphorus and potassium intake, we chemically analyzed phosphorus, potassium, sodium and

protein content of commonly consumed meat, poultry and fish (MPF) products. A food

frequency questionnaire administered to patients receiving dialysis (n=67) identified unbreaded

chicken, ground beef, steak, white fish, beef burgers, deli ham, shrimp and bacon as commonly

consumed MPF. Phosphorus and potassium content was significantly (P<0.05) higher in MPF

with versus without additives listed on ingredient list. Sodium-reduced MPF had significantly

(p<0.001) higher amounts of potassium from additives compared to original non-sodium reduced

counterparts. The use of additives in packaged MPF products significantly contribute to the

phosphorus and potassium loads in patients with CKD.

iii

ACKNOWLEDGMENTS

I would first like to thank my thesis supervisor, Dr. Pauline Darling, for her endless

support and guidance throughout the completion of my Master’s degree. I have learned an

invaluable amount from her expertise and methodical approach to research and am extremely

grateful for her dedication and generous time commitment to this study.

I am very appreciative of my committee members, Dr. Mary L’Abbé, Dr. Marc

Goldstein, Dr. Joanne Arcand and Dr. Berna Magnuson for the expert skill and knowledge they

each possess in their respective fields. Committee meetings were always a positive experience

due to their encouragement, helpful feedback and indispensable contributions.

I would like to recognize St. Michael’s Hospital for their assistance in this achievement,

as well as my colleagues at work. Particularly, Pamela Robinson and Jill Campbell for their

support in accomplishing my academic goals while working full time. My sincere thanks to my

dietitian colleagues; Carol Huang, Karen Burleigh, Alyson Martinez, Laura O’Brien and Dana

Whitham, for their sound advice and aid with the recruitment of patients. I am grateful for my

colleagues in hemodialysis and office mates who provided a listening ear when I needed it most.

Lastly, I would like to acknowledge and thank the patients that voluntarily took part in the study

and who inspire me with their perseverance in more ways than they know.

I am indebted to my wonderful family and friends for always being there for me. To my

husband, Sameer Parpia, whose own determination and diligent work ethic was my motivation to

do the same. From cooking meats with me for endless hours, providing statistical advice and

being a source of unwavering encouragement, the success of my masters would not have been

possible without his help and reassurance. Lastly, I would like to dedicate this thesis to my

parents for always supporting me in every way possible to ensure the success of my goals and

aspirations.

This research was funded and supported by a grant from the

Canadian Foundation for Dietetic Research.

iv

TABLE OF CONTENTS

ACKNOWLEDGMENTS .................................................................................................................... iii

LIST OF TABLES ............................................................................................................................ vii

LIST OF FIGURES ......................................................................................................................... viii

LIST OF APPENDICES ..................................................................................................................... ix

LIST OF COMMON ABBREVIATIONS ............................................................................................... x

1.0 Introduction ............................................................................................................................. 1

2.0 Literature Review ................................................................................................................... 3

2.1 Chronic Kidney Disease ....................................................................................................... 3

2.2 Nutritional considerations in chronic kidney disease ........................................................... 4

2.2.1 Protein-energy malnutrition and its complications in chronic kidney disease .......... 4

2.2.1.2 Dietary protein requirements ...................................................................... 4

2.2.1.2.1 Protein food sources ..................................................................... 5

2.2.2 Phosphorus, hyperphosphatemia and its complications in chronic kidney disease ... 5

2.2.2.1 Dietary phosphorus restriction ................................................................... 7

2.2.2.1.1 Phosphorus food sources .............................................................. 7

2.2.2.1.2 Phosphorus additives in foods ..................................................... 8

2.2.2.2 Phosphorus labelling regulations in Canada ........................................... 11

2.2.2.3 Phosphorus labelling regulations in United States .................................. 12

2.2.3 Potassium, hyperkalemia and its complications in chronic kidney disease ............. 13

2.2.3.1 Dietary potassium restriction ................................................................... 13

2.2.3.1.1 Food sources of potassium ......................................................... 14

2.2.3.1.2 Potassium additives in foods ...................................................... 15

2.2.3.2 Potassium labelling regulations in Canada .............................................. 16

v

2.2.3.3 Potassium labelling regulations in United States ..................................... 17

2.2.4 High sodium intake and its complications in chronic kidney disease ..................... 18

2.2.4.1 Dietary sodium restriction ........................................................................ 19

2.2.4.1.1 Food sources of sodium ............................................................. 19

2.3 Sodium reduction in Canada .............................................................................................. 20

2.3.1 Sodium Working Group ........................................................................................... 20

2.3.2 Strategies to reduce sodium in meat, poultry and fish products .............................. 21

2.3.2.1 Use of potassium additives in sodium reduction of foods ......................... 22

2.3.2.2 Use of phosphorus additives in sodium reduction of foods ...................... 23

3.0 Rationale and Objectives ...................................................................................................... 25

4.0 Commonly consumed meat, poultry and fish products among patients with End-

Stage Renal Disease at a Tertiary Care Teaching Hospital in Toronto, Canada: Food

Questionnaire.......................................................................................................................... 28

4.1 Introduction ........................................................................................................................ 28

4.2 Materials and Methods ....................................................................................................... 29

4.2.1 Design ...................................................................................................................... 29

4.2.2 Patient questionnaire development .......................................................................... 29

4.2.3 Face validation of patient questionnaire .................................................................. 30

4.2.4 Eligibility criteria ..................................................................................................... 30

4.2.5 Recruitment methods ............................................................................................... 31

4.2.6 Questionnaire administration and data collection .................................................... 31

4.2.7 Data analysis ............................................................................................................ 31

Results 4.4 ................................................................................................................................ 32

4.4.1 Participant recruitment ............................................................................................. 32

4.4.2 Demographic and clinical characteristics of participants ........................................ 32

4.4.3 Commonly consumed meat, fish and poultry products ........................................... 33

vi

4.4.4 Purchasing and preparation behaviours ................................................................... 33

4.4.5 Self-reported adherence to renal diet restrictions .................................................... 33

4.5 Discussion .......................................................................................................................... 43

4.5.1 Conclusions .............................................................................................................. 45

5.0 Phosphorus and potassium content of commonly consumed meat, poultry and fish

products among patients with CKD ..................................................................................... 46

5.1 Introduction ........................................................................................................................ 46

5.2 Materials and Methods ....................................................................................................... 47

5.3 Results ................................................................................................................................ 49

5.4 Discussion .......................................................................................................................... 57

6.0 Do Sodium Reduced Meat and Poultry Products Contain a Significant Amount of

Potassium and Phosphorus from Additives? ....................................................................... 61

6.1 Introduction ........................................................................................................................ 61

6.2 Materials and Methods ....................................................................................................... 62

6.3 Results ................................................................................................................................ 64

6.4 Discussion .......................................................................................................................... 70

7.0 Overall Discussion & Conclusions ....................................................................................... 73

7.1 Study Implications for Practice and Future Studies ........................................................... 76

REFERENCES ................................................................................................................................. 78

APPENDICES .................................................................................................................................. 93

vii

LIST OF TABLES

Table 2.1 Classification of stages of chronic kidney disease ………………………………..3

Table 2.2 Summary of studies examining phosphorus content by chemical analysis

in foods with and without phosphorus additives listed on the product label….....10

Table 4.1 Demographic and clinical characteristics of participants.…...…………………..35

Table 4.2 Ranked Consumption of meat, poultry and fish products based on

estimated weight (g) consumption per month by ESRD patients….………...…..37

Table 4.3 Ranked Sources of meat, poultry and fish products, based on

number of servings consumed per month by ESRD patients.………....…………39

Table 4.4 Purchasing, food preparation behaviours and self-reported adherence

to renal diet restrictions…….………………………….…………...…………….40

Table 4.5 Characteristics of study patients receiving hemodialysis as compared with

the Canadian Institute for Health Information data………..…………………….42

Table 4.6 Characteristics of study patients receiving peritoneal dialysis as compared

with the Canadian Institute for Health Information data…………………...……42

Table 5.1 Meat, poultry and fish food categories and comparable reference foods…..……51

Table 5.2 Characteristics of meat, poultry and fish (MPF) products commonly

consumed by patients with chronic kidney disease…………..………………….52

Table 5.3 Comparison of analyzed nutrient content among MPF categories containing

phosphorus additives, without phosphorus additives and reference foods….…...54

Table 5.4 Analyzed nutrient content of MPF categories with and without phosphorus

additives listed on the ingredient list and reference foods...……………………..55

Table 5.5 Comparison of analyzed nutrient content among chicken products labelled

seasoned, products not labelled seasoned and reference products………………56

Table 5.6 Comparison of analyzed nutrient content among MPF categories containing

potassium additives, not containing potassium additives and reference foods..…56

Table 6.1 Comparison of analyzed nutrient levels in paired sodium reduced and original

(non-sodium reduced) meat and poultry products………...……….........……….65

Table 6.2 Comparison of sodium reduced, original (non-sodium reduced), and

reference meat and poultry products……………………………………….…….66

Table 6.3 Chemical analysis of sodium, potassium, phosphorus and protein content of

paired original (non-sodium reduced) and sodium-reduced meat and poultry

products…………………………………………………………………………..67

viii

LIST OF FIGURES

Figure 4.1 Flow diagram of subject recruitment and study completion……………………..34

Figure 5.1 Percent of MPF foods containing phosphorus additives on the ingredient list

according to MPF category……………………………………………………....53

Figure 6.1 Presence and type of additives in original and sodium reduced meat and

poultry products (MPP)…………………………………………………………..69

ix

LIST OF APPENDICES

Appendix A Food questionnaire…………..…………………………………………………..93

Appendix B Face validation recruitment pre-amble……...………………………………….119

Appendix C Recruitment pre-amble…………………………………………..……………...122

Appendix D Patient consent form…………………………………………….……………...125

Appendix E Data collection form…………………………………………..………………...129

Appendix F Comparison of store brands and national brands among major subgroups

of MPF foods...…………………………………...…………………………….131

Appendix G Comparison of analyzed nutrient content among processed and minimally

processed foods………………...……………………………………………….133

Appendix H Comparison of analyzed nutrient content among breaded chicken products…...135

Appendix I The accuracy of Canadian Nutrient File data for reporting phosphorus, potassium,

sodium and protein in commonly consumed MPF products………...…………137

x

LIST OF COMMON ABBREVIATIONS

CFIA Canadian Food Inspection Agency

CKD Chronic Kidney Disease

CNF Canadian Nutrient File

CVD Cardiovascular Disease

ESRD End-Stage Renal Disease

FDA Food and Drug Administration

K Potassium

K/DOQI Kidney Disease Outcome Quality Initiative

KDIGO Kidney Disease: Improving Global Outcomes

MPF Meat, Fish and Poultry

MPP Meat and Poultry Products

Na Sodium

NFt Nutrition Facts Table

P Phosphorus

PEM Protein Energy Malnutrition

Pro Protein

SMH St. Michael’s Hospital

USDA United States Department of Agriculture

1

1.0 Introduction

Chronic kidney disease (CKD) is increasingly prevalent and associated with high

morbidity and mortality (Kovesdy et al, 2006). The progressive decline in kidney function leads

to the retention of substances, such as phosphorus, potassium and sodium, and is associated with

adverse outcomes (Kopple & Massry, 2004). High serum phosphorus levels have been

independently associated with increased cardiovascular mortality, while a high potassium

concentration can lead to fatal cardiac arrhythmias (Putcha & Allon, 2007; Palmer et al, 2011).

Dietary approaches aim to address these abnormalities by dietary restriction of these nutrients in

the diet of patients with CKD.

In 2010, the Sodium Working Group was established to develop a population health

strategy to lower the dietary sodium intake of Canadians and has set a 2016 interim goal for

mean population consumption of sodium at 2300 mg per day. A pillar of the sodium reduction

strategy was the voluntary reduction of sodium levels in packaged foods (Health Canada, 2010).

Sodium plays a key role in the microbial safety and the flavor profile in many foods including

meat, poultry and fish products (Doyle & Glass, 2010). Hence, replacement of sodium or salt

with a sodium analogue that provides similar functional effects is often required. One of the

many ways food manufacturers can reduce sodium levels in meat, poultry and fish food items is

to replace the sodium with additives such as potassium additives or phosphorus additives

(Desmond, 2006).

In recent years, phosphorus additives have been identified as a significant contributor to

dietary phosphorus intake (Carrigan et al, 2014; Leon et al, 2013; Bell et al, 1977). Phosphorus

additives are found in a wide variety of foods, and can provide favorable effects, such as

improving texture and shelf-stability (Lampila, 2013). However, these additives are almost

entirely bioavailable and can contribute to elevated serum phosphorus levels (Calvo et al, 2014).

Potassium additives provide a salty flavor, and potassium chloride is the most frequently

used replacement for sodium chloride (table salt) (CTAC, 2009). However, the use of potassium

salts has been associated with toxicity in patients with impaired renal handling of potassium

(Doorenbos & Vermeij, 2003). Additional additives, such as potassium lactate and potassium

2

phosphates, may also be used in the sodium reduction of foods but there are few studies

describing the potassium content of foods with additives.

The potassium and phosphorus contents in foods are not listed on the nutrition facts table.

Therefore, it is difficult to determine the contribution of phosphorus and potassium additives to

the levels of nutrients in foods. Furthermore, studies have demonstrated that nutrient databases

often underestimate the phosphorus content in foods with additives (Sullivan et al, 2007).

Accurately estimating the phosphorus and potassium content in foods is crucial in order for

clinicians to make proper dietary recommendations for patients with CKD and for patients to

choose appropriate foods in accordance with their renal diet. This in turn may help prevent

hyperphosphatemia, hyperkalemia and their respective complications.

Dietary protein requirements are increased in patients with end-stage renal disease who

are receiving dialysis treatment. Given that meat, poultry and fish products represent rich sources

of dietary protein, these patients are encouraged to increase their intake of these products. In

addition to a high protein diet, these patients also require a low sodium diet of less than 2000 mg

per day (Kidney Disease: Improving Global Outcome (KDIGO), 2012). This creates additional

concern as patients are educated to read labels and choose low sodium food products

(Vennegoor, 2009), which may unintentionally lead to an increased intake of phosphorus and

potassium.

Thus, the overall aim of this dissertation is to enhance knowledge of the amounts of

phosphorus, potassium and protein content in commonly consumed meat, poultry and fish

products among the CKD population, and to determine whether the sodium reduction of these

foods is associated with increased use of phosphorus and potassium additives.

3

2.0 Literature Review

2.1 Chronic Kidney Disease

Chronic kidney disease (CKD) is defined as ‘abnormalities of kidney structure or

function, present for at least 3 months, with implications for health’ (KDIGO, 2012). There is a

high prevalence of CKD in Canada as it is estimated to affect approximately 3 million Canadians

(Arora et al, 2013). Leading risk factors for CKD include diabetes mellitus and hypertension.

The estimated glomerular filtration rate is a common measure of kidney function and is

used to establish the five progressive stages of kidney disease (Levey et al. 2011) (See Table

2.1). Generally, symptoms and complications of CKD are not seen until the later stages of kidney

disease. Once the estimated glomerular filtration rate falls below 15 mL/min/1.73m2, the patient

is considered to be at Stage 5 kidney disease or end-stage renal disease (ESRD), wherein he/she

will require a form of renal replacement therapy. The two types of renal replacement therapy are

a kidney transplant or dialysis. Dialysis is a treatment that purifies blood and the two main forms

are hemodialysis and peritoneal dialysis. In 2012, over 40,000 Canadians received renal

replacement therapy, which is a 40% increase from 2003. More specifically, 58% were receiving

dialysis therapy and the remaining 42% had a functioning kidney transplant (Canadian Organ

Replacement Register (CORR), 2014).

As the kidneys are vital organs responsible for the filtration of blood, removal of waste

products and production of hormones, the progressive deterioration of kidney function leads to

many health complications. Furthermore, CKD is associated with a significant increased risk of

cardiovascular and all-cause mortality (Rosenberg, 2014).

Table 2.1 Classification of stages of chronic kidney disease

GFR Stage GFR (mL/min per 1.73 m2) Relative kidney function

1 >90 High or optimal

2 60-89 Mildly decreased

3a 45-59 Mildly to moderate decreased

3b 30-44 Moderately to severely decreased

4 15-29 Severely decreased

5 <15 Kidney failure or end-stage renal disease

Adapted from KDIGO 2012: Practice Guidelines for the Evaluation and Management of CKD

4

2.2 Nutritional considerations in chronic kidney disease

As CKD progresses, there is decreased renal clearance of solutes, including sodium,

potassium, phosphorus and water, which leads to the retention of these nutrients in the body. In

addition, decreased gastrointestinal absorption of nutrients, such as calcium and vitamins, can

contribute to deficiencies (Kopple & Massry, 2004). Furthermore, there are increased losses of

amino acids, protein and water-soluble vitamins during dialysis therapy itself (Ikizler et al,

1994). As a result, patients with CKD, who have varying levels of kidney function, multiple

comorbidities and different dietary intake patterns, require individualized dietary modifications

to compensate for the many factors that affect nutritional status.

2.2.1 Protein-energy malnutrition and its complications in chronic kidney disease

CKD can lead to metabolic acidosis, persistent inflammation and increased

glucocortocoid activity, all of which can lead to increased protein catabolism. In addition,

patients on dialysis have increased amino acid losses during dialysis, thus further increasing their

protein needs (Carrero et al, 2013). In combination with factors such as loss of appetite,

increased energy expenditure, decreased anabolism and comorbidities, patients with CKD are at

a high risk of developing protein-energy malnutrition (PEM) (Carrero et al, 2013).

The prevalence of PEM among patients with CKD is high, varying from 18-75% across

studies (Foque et al, 2008). While the majority of patients have a mild to moderate forms of

PEM, approximately 10% of patients have a severe form (Kuhlmann et al, 2007). Studies have

shown that there is a strong association with PEM and increased morbidity and mortality in

patients with CKD (Kalantar-Zadeh et al, 2004). Therefore a cornerstone of nutrition therapy in

renal disease involves the prevention and treatment of PEM. Strategies may include the use of

oral nutritional supplements, changes in the dialysis prescription to stimulate appetite, and

optimizing dietary protein and energy intake at meals and snacks.

2.2.1.2 Dietary protein requirements

The 2012 Kidney Disease, Improving Global Outcomes (KDIGO) clinical practice

guidelines for the evaluation and management of CKD (KDIGO, 2012) suggest a protein intake

of 0.8 g/kg/day, with avoidance of high protein intakes (>1.3 g/kg/day) in adults who are not on

dialysis with a GFR <30 mL/min/1.73m2 (Stage 4 and 5). The KDIGO work group concluded

5

that a low dietary protein intake (< 0.8 g/kg/d) did not offer an advantage in the progression of

kidney disease, while excess dietary protein leads to the accumulation of uremic toxins in later

stages of CKD.

In contrast, once a patient’s kidney disease has progressed to a point where they require

dialysis therapy, protein requirements increase due to losses of protein during the dialysis

procedure and greater protein catabolism in end stage renal disease. The Kidney Disease

Outcomes Quality Initiative (K/DOQI, 2000) clinical practice guidelines for protein intake for

chronic dialysis patients suggest that patients receiving hemodialysis consume 1.2 g/kg/day,

while patients receiving peritoneal dialysis ingest 1.2-1.3 g/kg/day of protein. This is because

patients receiving peritoneal dialysis have increased protein losses compared with those on

hemodialysis. These recommendations were determined by several nitrogen balance studies, as

this was considered the classical method to determine dietary protein requirements (Kopple,

2001; Food & Nutrition Board, 1989). However, many of these studies were small and contained

methodological limitations, such as short study durations, variations in hemodialysis treatments,

and included patients with acute superimposed illnesses and/or PEM (Kopple, 2001).

2.2.1.2.1 Protein food sources

A qualifying statement included in the K/DOQI protein intake guidelines states that “at

least 50% of the dietary protein should be of high biological value”. A food that is high in

protein quality refers to a protein that has similar amino acid profile to human protein and is

efficiently utilized by the body (K/DOQI, 2000). Dietary protein sources that are high in protein

quality are generally sources of animal protein such as meat, poultry, fish, eggs and dairy (Jadeja

& Kher, 2012). Plant sources of protein that are also high in protein quality include soy, legumes,

nuts and seeds, but these foods contain a high amount of potassium and phosphorus and

consumption is generally limited in a renal diet (Kalantar-Zadeh et al, 2010).

2.2.2 Phosphorus, hyperphosphatemia and its complications in chronic kidney disease

Phosphorus is a non-metal element essential for normal cell function in all living

organisms as it is a component of phospholipids, nucleic acids and adenosine triphosphate

(Knochel, 2006). Phosphorus is mostly found in the bones and teeth, however ~1% is found in

extracellular fluid and blood and is tightly regulated by the parathyroid hormone and fibroblast

growth factor (IOM, 1997). After intestinal phosphorus absorption, excess dietary phosphorus is

6

mainly excreted through the kidneys where phosphorus is filtered at the glomerulus and

reabsorbed in the proximal tubule in order to maintain serum phosphorus levels within the

normal range (Kalantar-Zadeh et al, 2010).

Hyperphosphatemia, or elevated serum phosphorus concentration above the normal range

(0.85-1.45 mmol/L), is a common condition in persons with CKD. It is associated with numerous

conditions such as extraskeletal calcification, renal osteodystrophy and secondary

hyperparathyroidism (Palmer et al, 2007; Albaaj et al, 2003; Friedman et al, 2005; Tomiyama et

al, 2006). In addition, hyperphosphatemia is associated with an increased risk of mortality in

individuals with advanced stages of CKD (Block et al, 1998; Kestenbaum et al, 2005; Palmer et

al, 2011). Remarkably, recent studies conducted in the general population have even shown an

association between higher serum phosphorus levels and/or higher dietary phosphorus intake and

adverse cardiovascular outcomes (Dhingra et al, 2007; Tonelli et al, 2005; Chang et al, 2014).

While the exact mechanism is not clear, it is thought that in the presence of secondary

hyperparathyroidism, calcium phosphate precipitation leads to vascular calcification and a

subsequent increase in cardiovascular disease, which is the leading cause of death in CKD

(Kendrick & Chonchol, 2011). Despite this strong association and plausible mechanism, it is

important to note that there have been no randomized clinical trials to date showing that lowering

serum phosphorus concentration results in a reduction in mortality (Navaneethan et al, 2009;

Palmer et al, 2007; Strippoli et al, 2006).

Interventions aimed at controlling serum phosphorus levels include reducing intestinal

absorption with phosphorus binding medication, removing phosphorus with dialysis therapy, and

dietary phosphorus restriction. The pill burden of dialysis patients has been shown to be the

highest of any chronic disease states, and phosphate binding medication can contribute up to half

of the daily pill burden. There is a high reported non-adherence rate to phosphate binder

medication of approximately 60% (Chiu et al. 2009). Moreover, phosphorus removal during

dialysis therapy is also limited to 2100-2700 mg per week (Kuhlmann, 2010). Therefore,

modification of the dietary phosphorus load plays a crucial role in the normalization of serum

phosphorus levels in CKD.

7

2.2.2.1 Dietary phosphorus restriction

As per the K/DOQI clinical practice guidelines for bone metabolism and disease in CKD

(2003), patients with hyperphosphatemia are advised to restrict their dietary intake of phosphorus

to between 800 and 1000 mg per day. K/DOQI recommends that patients with stage 3 and 4

CKD maintain their serum phosphorus levels between 0.87 and 1.49 mmol/L, while stage 5

patients with CKD maintain a phosphorus level less than 1.78 mmol/L. While evidence suggests

that educating patients about dietary phosphorus restriction decreases serum phosphorus levels

(Caldeira et al, 2011), there are no randomized controlled trials showing that dietary phosphorus

restriction leads to improved cardiovascular outcomes. Hence, the more recent KDIGO clinical

practice guidelines for bone mineral disorders (2009) suggest that dietary phosphorus intake be

limited, but that there was insufficient data to prescribe a dietary phosphorus restriction as the

primary intervention in the management of hyperphosphatemia. In addition, the KDIGO authors

did not provide any specific guidance on dietary phosphorus amount that should be ingested,

likely due to lack of evidence. Further studies may help to establish more specific

recommendations regarding the daily dietary phosphorus intake in patients with CKD.

2.2.2.1.1 Phosphorus food sources

According to the NHANES 2005-2006 survey of the general US population, men

between the ages of 19-50 consumed more than 1600 mg phosphorus per day, while women of

the same age consumed over 1100 mg phosphorus per day (Calvo & Uribarri, 2013). About 20-

30% of the dietary phosphorus intake in the general population comes from meat, fish, poultry,

milk and eggs (Calvo & Park, 1996). Since animal products are a significant source of

phosphorus, there is a close association between phosphorus and the protein content of food

(Boaz and Smetana, 1996). Although the K/DOQI guidelines (2000) recommend increased

protein intake for patients with ESRD on dialysis (1.2 g/kg/day), evidence suggests that a diet

with this protein level will lead to hyperphosphatemia in patients on dialysis (Uribarri & Calvo,

2003). Paradoxically, Shinaberger et al (2008) showed that participants who had a fall in serum

phosphorus concentration and had a low dietary protein intake were at increased risk of death,

presumably related to protein wasting and malnutrition. Patients whose protein intake increased

while their serum phosphorus declined showed the greatest survival benefit, possibly because

this mitigates the mortality risk associated with hyperphosphatemia and PEM. The K/DOQI

guidelines (2003) have suggested choosing foods with a low phosphorus to protein ratio as it

8

focuses on both lowering dietary phosphorus intake as well as ensuring sufficient protein intake

to optimize nutritional status of patients with CKD, and is independent of serving size.

Other dietary sources of phosphorus include whole grains, legumes, nuts and dairy

products. The bioavailability of organic phosphorus, from animal sources and plant sources, is

approximately 40-60%, with phosphorus from animal sources more effectively absorbed than

plant sources (Uribarri, 2007; Calvo et al, 2014). Phosphorus from plant-based proteins have

lower digestibility as they are in the storage form of phytate. Since most mammals lack the

enzyme phytase, only 20-50% of phosphorus from nuts, legumes and grains are absorbed in the

gastrointestinal tract. Moe et al (2011) conducted a crossover trial with nine pre-dialysis CKD

patients who consumed one week of a vegetarian diet or meat diet containing equivalent amounts

of phosphorus. The results demonstrated the group consuming a vegetarian diet had lower serum

phosphorus levels than the meat diet group, indicating that the source of dietary phosphorus is an

important factor in determining serum phosphorus concentrations.

2.2.2.1.2 Phosphorus additives in foods

Inorganic sources of phosphorus require no enzymatic digestion, and are easily and

rapidly absorbed with a bioavailability of 80-100% (Calvo et al, 2014). Sources of inorganic

phosphorus include processed foods, such as restructured meats, processed cheeses, instant

products (puddings), refrigerated bakery products and certain beverages as they often contain

phosphorus additives. Phosphorus additives are used by food manufacturers for their ability to

extend shelf-life, improve colour, retain moisture, emulsifying properties and as a leavening and

anti-caking agent (Kalantar-Zadeh et al, 2010).

Adherence to a dietary phosphorus restriction has become increasingly difficult due to the

addition of phosphorus additives to food, which was reported to contribute up to 1000 mg

phosphorus/day to the average American diet (Bell et al, 1977; Uribarri and Calvo, 2003). A

recent unpublished study in Ontario scanned the package labels of meat, poultry and fish (MPF)

products in grocery stores in the Waterloo region. The authors reported that 43% of packaged

meat products had a phosphorus additive listed on the ingredient list (Cafferty et al, 2014

abstract). More specifically, deli meats had the highest prevalence of phosphorus additives on the

ingredients list (78.3%), followed by frozen fish (60.4 %) and frozen chicken products (57.3%).

Studies reporting the chemical analysis of packaged foods in the United States (U.S.) and Europe

9

showed that the addition of phosphorus additives significantly increases the phosphorus content

of the food items by as much as 66% (see Table 2.2). To our knowledge, no such studies have

taken place in Canada.

U.S. studies have demonstrated a high variability in the use of phosphorus additives in

the food supply, and have shown that the United States Department of Agriculture (USDA)

national nutrient database underestimates the phosphorus content of foods which contain

additives (Sullivan et al, 2007). It is therefore not usually clear to the consumer that such

products may have elevated amounts of phosphorus. Bell et al. (1977) completed a crossover

trial in which 8 healthy volunteers were fed two isocaloric diets; one with additives and one

without phosphorus additives. The high phosphorus additive diet led to increased serum

phosphorus levels and urinary phosphorus excretion. Thus, the wide array of food sources

containing phosphorus additives can contribute to hyperphosphatemia in patients with CKD and

result in difficulties maintaining a lower phosphorus intake level (Sherman and Mehta, 2009a).

In Canada, phosphorus content is usually not listed on Nutrition Fact tables, adding to the

difficulty of estimating phosphorus content of foods with additives. Currently, patients are

educated to avoid foods with a phosphorus additive listed on the ingredient list (ORN, 2013).

Reading ingredient lists can be an arduous task for patients with CKD and eliminating all foods

listing a phosphorus additive can greatly limit food choices. However, a randomized controlled

trial was conducted by Sullivan et al. (2009) in which the intervention group received education

to read the ingredients list and avoid foods that listed a phosphorus additive, while the control

group received usual care. The results indicated that patients educated to avoid phosphorus

containing food additives resulted in modest (0.2 mmol/L), but significant decreases in serum

phosphorus levels.

10

Table 2.2 Summary of studies examining phosphorus content by chemical analysis in foods with

and without phosphorus additives listed on the product label

Author

Year

Country

Method Key Findings

Lou-Arnal et al.

2014

Spain

118 various types of processed

foods

Higher P content and P:Pro ratio

in foods with P Additives (P

content varies per food group)

Carrigan et al.

2014

United States

Low additive vs. additive

enhanced diet (4-day)

60% higher P content in additive

enhanced diet

Léon et al.

2013

United States

56 top selling grocery items with

and without P additives

4-day sample meals with and

without P additives

60% more P in top-selling foods

with P additives

70% higher P content in sample

meals with P additives

Cupisti et al.

Nov 2012

Italy

40 samples of ham with and

without P additives

Measured inorganic P content

66% more inorganic phosphorus

in ham with P additives

Benini et al.

2011

Italy

60 samples of cooked ham, roast

turkey breast and roast chicken

breast with and without P

additives

57% higher total P content in

food items with P additives

Sherman et al.

2009a

United States

36 uncooked enhanced* products

and unenhanced meat and

poultry products

28% higher P:Pro ratio in food

items enhanced with P additives

Sherman et al.

2009b

United States

44 meat, poultry and fish

products with and without

phosphorus additives

62% higher P:Pro ratio in food

items with P additives

Sullivan et al.

2007

United States

38 chicken products with and

without P additives

Chicken with P additives

significantly increase the amount

of P in products.

USDA nutrient database

underestimates P content of

foods with P additives

Abbreviations: P = Phosphorus; Pro = Protein; USDA = United States Department of Agriculture

11

2.2.2.2 Phosphorus labelling regulations in Canada

It is not mandatory to report the phosphorus content of foods on the Nutrition Facts table

(NFt) in Canada. When voluntarily displaying phosphorus content, it is depicted as a percentage

of the daily value, and not it milligrams. The daily value for phosphorus represents the percent

amount of phosphorus that a serving of food provides, based on the recommended daily intake of

1100 mg/day (CFIA, 2015a). Hence, consumers generally do not know the amount of

phosphorus that is in a particular food item and if it is listed on the NFt, it is in the form of a

percent of daily value, which may be difficult to interpret. In addition, Health Canada has

recently proposed for the daily value of phosphorus to be based on the increased reference intake

of 1250 mg/day (Health Canada, 2015a).

In Canada, compositional standards in both the Food and Drug Regulations (FDR) and

the Meat Ingredient Regulations (MIR) allow for the addition of phosphate salts and/or water to

meats, including solid cut meat products (i.e. pork roasts), chopped and formed meat products

(i.e. ground meat) and prepared meat products (i.e. sausages) (CFIA, 2013). These solutions are

added or injected into meat and poultry products to help enhance moisture in meat products,

reduce purge, and increase shelf-life (Murphy-Gutekunst, 2005). According to Canadian food

labelling regulations (CFIA, 2013), the term “seasoned” is used when phosphate salts or spices

with water are injected or incorporated into the “solid cut” meat product (i.e. “seasoned chicken

breast”). The total maximum level of phosphate salts that can be added to MPF products is 0.5%

by weight, calculated as sodium phosphate dibasic added to the product (CFIA, 2013). The

contribution of phosphorus at 0.5% by weight varies based on the type of phosphate salt used,

but can range from approximately 100-150 mg phosphorus per 100 grams of MPF. Phosphate

salts, such as sodium phosphate, must be declared on the list of ingredients on both plant packed

and retail packed solid cut meats. Exemptions to this rule include side bacon, Wiltshire bacon,

pork jowls and salt beef. In addition, unpackaged meat items that are sold behind a meat or deli

counter and cured products (i.e. ham) that are packed at retail, are not required to labelled (CFIA,

2013).

If phosphorus additives are used, they must be declared in the ingredients list of pre-

packaged products, however, they do not need to be quantified and listed by weight of the

product. Also, if the product contains more than one phosphorus additive, it can be collectively

12

listed as “sodium phosphates” (CFIA, 2015b). Common phosphorus additives that are used in

meat products include, disodium phosphate, potassium phosphate, sodium acid pyrophosphate

and tetrasodium pyrophosphate (CFIA, 2015b).

2.2.2.3 Phosphorus labelling regulations in United States

Similar to Canadian regulations, the phosphorus content is not required to be listed on the

Nutrition Facts label in the U.S. If manufacturers voluntarily disclose phosphorus content, it is

also displayed as a percentage of daily value. The daily value in the U.S. is 1000 mg phosphorus

per day, which is slightly lower than the Canadian daily value. However, the U.S., like Canada,

has proposed an increase in the daily value to 1250 mg/day (FDA, 2014c).

Phosphorus additives are categorized as foods additives considered to be ‘generally

recognized as safe (GRAS)’. The term GRAS indicates that the ingredient or additive is not

known to have harmful effects under prescribed conditions of use. These products are exempted

from FDA’s testing and approval process for food additive use (USDA, 2007). As of 2009,

eleven phosphate salts were approved for use in meat products in the U.S., five of which were

potassium salts (Sherman and Mehta, 2009b).

According to Food Safety and Inspection Service (FSIS, 2015) phosphorus additives,

including potassium phosphates, can be added or injected in amounts that total up to 0.5% of the

product formula of meat and poultry products. Fish and seafood falls under the regulations of the

Food and Drug Administration (FDA), which allow sodium phosphate to be included according

to good manufacturing practice (FDA, 2014b). Good manufacturing practice (GMP) specifies

that the “quantity of the ingredients added to food does not exceed the amount reasonably

required to accomplish the intended physical, nutritional, or other technical effect in food” (FDA,

2014a). Hence, unlike Canada, there is no maximum limit specified for the amount of sodium

phosphate added to fish and seafood products in the U.S.

Phosphorus additives must be listed on the ingredient list, and if there is more than one

sodium phosphate in the food item, it can be collectively listed as sodium phosphates (USDA,

2010). Similarly, ‘potassium phosphates’ is the collective name that can be used for more than

one potassium phosphate.

13

Typically, the term ‘enhanced’ is used for a meat or poultry product that has been

injected with a solution that may contain phosphate salts. However, FSIS (2014) recently issued

a new rule which will prohibit the use of the term enhanced effective January 1st, 2016. New

labeling will include a phrase declaring the product “contains x% solution”, as well as providing

individual ingredients of the solution listed in descending order by weight.

2.2.3 Potassium, hyperkalemia and its complications in chronic kidney disease

Potassium is the most abundant intracellular cation in the body, with 98% of potassium

contained inside the cells and only 2% in the extracellular compartment (Putcha & Allon, 2007).

Small changes in extracellular or serum potassium concentrations can affect neural transmission,

muscle contraction and vascular tone (IOM, 2005). In individuals with normal kidney function,

90-95% of dietary potassium is excreted through the kidneys, while the remaining amount is

excreted in the stool (Putcha & Allon, 2007). Potassium is easily filtered by the glomerulus and

the majority of filtered potassium is reabsorbed in the proximal tubule and loop of Henle

(Palmer, 2014). As the kidneys are largely responsible for the excretion of potassium, patients

with CKD are at a greater risk of developing hyperkalemia.

Hyperkalemia is defined as a serum potassium level that is greater or equal to 5.5 mmol/L

(Jamison, 2001). If serum potassium concentration increases to high levels, it can lead to cardiac

arrhythmias. Furthermore, sudden cardiac death is the most common cause of death in patients

on hemodialysis, and it is often caused by fatal arrhythmias (Sanghavi et al, 2013).

Hyperkalemia occurs frequently in patients with chronic kidney disease (CKD) as they have a

decreased ability to excrete potassium through their kidneys. There are many causes of

hyperkalemia which include, but are not limited to, inadequate dialytic potassium removal,

medications that reduce urinary potassium excretion, insulin deficiency, metabolic acidosis,

severe constipation and excess dietary intake of potassium (Putcha & Allon, 2007).

2.2.3.1 Dietary potassium restriction

The recommended daily intake of potassium for an individual with moderate to severe

kidney disease is 2000-3000 mg/day (Nelms et al 2007) or 1 mmol (39 mg)/kg of ideal body

weight (Byham-Gray & Wiesen, 2005; ADA & DC, 2000). This is significantly lower than the

Adequate Intake (AI), which recommends 4700 mg/day in the general population (IOM, 2005).

The AI is based on the Dietary Approaches to Stop Hypertension (DASH) diet study which

14

demonstrated that along with a low sodium diet, a high intake of dietary potassium from sources

such as fruits, vegetables and low-fat dairy products resulted in significant decreases in blood

pressure in the healthy population (Sacks et al, 2001). However, both Canadian and U.S.

populations appear to consume low amounts of potassium which fall below the recommended

intake level. The Total Diet Study used CCHS 2.2 food intake data to determine that 68.5-98.8%

of Canadians were consuming less potassium than the AI, across all age groups (Tanase et al,

2011). In the U.S., the average potassium intake of people 2 years and older is 2640 mg/day

according to NHANES 2009-2010 data (Hoy & Goldman, 2012).

Although no clinical trials have examined the effects of a dietary potassium restriction on

preventing hyperkalemia, studies have demonstrated that an oral potassium load (0.25 mmol/kg

body weight) can produce a significant increase in serum potassium in patients with end-stage

renal disease (Allon et al, 1993; Fernandez et al, 1986). Thus, it is presumed that excessive

dietary potassium intake in CKD can lead to hyperkalemia which is associated with fatal

arrhythmias. In one study by Noori et al (2010), higher dietary potassium intake, as estimated by

a food frequency questionnaire, was associated with increased mortality in patients on

hemodialysis.

2.2.3.1.1 Food sources of potassium

A food containing a high amount of potassium is commonly considered to have >200 mg

potassium per serving. The highest sources of dietary potassium include fruits, vegetables,

legumes and dairy products (Sanghavi et al, 2013). However, even a low potassium food can

significantly contribute to daily potassium intake if consumed in large quantities. Therefore,

guidelines for potassium intake often specify a maximum daily serving size for low to moderate

potassium containing foods (ORN, 2013).

According to NHANES data from 2009-2010, fruits and vegetables contributed 20% of

dietary potassium intake in the US, while meats and poultry contributed 10% of total intake (Hoy

& Goldman, 2012). According to Canadian Community Health Survey (CCHS) 2.2 data, the

contribution of potassium from MPF increased with age. Men and women between the ages of

19-70 consumed 14.1% and 12% of their potassium intake from MPF, respectively (Tanase et al

2011). The major source of dietary potassium in Canada came from milk and dairy products

(Tanase et al, 2011).

15

Commercially available salt substitutes are often in the form of potassium chloride and

contain very high amounts of potassium. For instance, the salt-substitute brand Nu-Salt®

contains 3144 mg per teaspoon (www.nusalt.com), which is more than the recommended daily

intake for a patient requiring a potassium restriction. The salty flavor of potassium chloride and

its high potassium content has raised questions about the potential therapeutic role of salt

substitutes in exerting a blood pressure lowering effect. The China Salt Substitute Study (2007)

was a randomized controlled trial that compared the effects of a salt substitute (65% sodium

chloride, 25% potassium chloride, 10% magnesium sulphate) versus sodium chloride on a rural

Chinese population. Results demonstrated that after one-year, participants receiving a salt

substitute had significantly lower blood pressure and the salt substitute was generally well

accepted by participants (Li et al, 2009).

However, there have been several case-reports of life-threatening hyperkalemia due to

salt substitute use in patients with CKD, as well as patients with impaired renal potassium

handling (Ray et al, 1999; Doorenbos & Vermeij, 2003; John et al, 2011). Medical conditions

associated with impaired renal potassium handling include diabetes, severe heart failure, adrenal

insufficiency and kidney disease (IOM, 2005). In addition, medications such as potassium-

sparing diuretics, angiotensin converting enzyme inhibitors and angiotensin receptor blockers

can significantly impair urinary potassium excretion (IOM, 2005). Due to the increased

prevalence of conditions causing impaired potassium excretion and widespread use of

potassium-sparing medications, the number of people at risk for hyperkalemia is likely to

increase (Doorenbos & Vermeij, 2003). It is therefore imperative that patients are educated about

the potential adverse effect of salt substitutes due to its high potassium content.

2.2.3.1.2 Potassium additives in foods

There are many potassium additives that are used in various food products, such as

potassium chloride, potassium lactate, potassium phosphates, potassium sorbate, and potassium

citrate, among others. Potassium chloride is the most frequently used substitute for sodium

chloride, due to its salty taste and functional effects. Potassium lactate and potassium phosphate

are often used to improve shelf-life, retain moisture and improve texture in meat and poultry

products (Desmond, 2006).

16

To our knowledge, there is no Canadian study that has reported the amount of potassium

in food products which contain potassium additives. Sherman and Mehta (2009b) chemically

analyzed the potassium content of 36 uncooked meat and poultry products in the United States

and found large variability between products. The authors noted the top five enhanced products

with the most potassium contained 692-930 mg potassium per 100 grams, which is significantly

greater than the average potassium content of meat and poultry products of the same weight

(~300-375 mg/100g).

Approximately 85% of dietary potassium is absorbed in the healthy individual (Holbrook

et al, 1984), however bioavailability is much higher with potassium salts. Braschi et al (2009),

substituted 30% of sodium in bread with potassium salts and determined that the incorporated

potassium chloride was entirely bioavailable.

2.2.3.2 Potassium labelling regulations in Canada

Information regarding the potassium content of foods is generally not available for

consumers on the Nutrition Facts table (NFt). Health Canada specifies that it is only mandatory

for food manufacturers to list the potassium content on the NFt, if there is a specific product

claim such as “a source of potassium” or “sodium-reduced” with the use of potassium salts

(CFIA, 2014, CFIA 2015b). The food item needs to contain 350 mg of potassium or more in

order to be considered a source of potassium and the amount of potassium must be listed on the

NFt if this claim is used. The daily value listed on the NFt is based on an intake of 3500 mg

potassium per day, however Health Canada has proposed to increase this amount to 4700 mg per

day (Health Canada, 2015a).

Health Canada allows for a disease risk reduction claim with respect to sodium and

potassium that manufacturers can display on their product label. An example of a disease risk

reduction claim is “a healthy diet containing foods high in potassium and low in sodium may

reduce the risk of high blood pressure, a risk factor for stroke and heart disease. (Naming the

food) is a good source of potassium and low in sodium”. Manufacturers may perceive the

addition of potassium to foods to be advantageous for the general population. This perceived

advantage may in turn lead to further additions of potassium to the food supply in the form of

additives, and poses concern for those with CKD.

17

Health Canada (2012b) permits the use of potassium lactate in cooked and uncooked

meat and poultry products as it is an antimicrobial agent that prevents spoilage. Potassium lactate

was approved for use for injection and/or a cover solution for the curing of meat and poultry

products in amounts that were equivalent to 2-4% of the product’s weight (Health Canada,

2012b). At its maximum use (4%) this would contribute 1200 mg of potassium to a 100 g meat

or poultry product. Health Canada’s safety assessment of potassium lactate determined that “the

additional dietary intake of potassium per person on a daily basis would be up to 2471 mg

potassium per day” (Personal communication with Mr. P Loeven, Health Canada Aug 7, 2013).

This is a concerning amount of potassium, especially for those patients with CKD requiring a

potassium restriction of 2000 mg of potassium per day.

When potassium chloride is used as a sodium replacer, it is considered a food ingredient

(seasoning) as it provides flavor enhancement, rather than a technological purpose. As of

September 2013, potassium chloride was no longer considered a food additive; therefore

regulations surrounding its use are less specific. Under the FDR there is no established maximum

use in foods, including meat, poultry and fish products (Personal communication with Ms

Lindsay Lukeman, Health Canada 6 May 2015). However, there are certain foods (i.e. white

bread) where salt replacers, such as potassium chloride, are not permitted.

It is important to note that Health Canada recently proposed that potassium be included in

future NFt on all packaged products (Health Canada, 2015b). If the proposed changes are

approved, it would provide important information to help guide those who need to limit dietary

potassium.

2.2.3.3 Potassium labelling regulations in United States

In the U.S., it is not mandatory for food manufacturers to display the potassium content

on the package label of food items. Potassium content declaration is only mandatory if a

potassium-related claim is made on the food (FDA, 2014c). The percent daily value established

for potassium is 3500 mg per day, which is significantly less than the AI (FDA, 2013). A study

based in the United States analyzed over 6000 food products and determined that potassium

content was displayed on the label of less than 10% of food products (Curtis et al, 2013). In

2014, it was proposed that in the future, potassium content be included on the Nutrition Facts

label (FDA, 2014c)

18

Potassium chloride has GRAS status in the U.S. and has been approved by FSIS (2012)

as a tenderizing agent in raw poultry and meat cuts in amounts up to 3%. The FDA has approved

its use in fish and seafood products with no limitation other than good manufacturing practice

(FDA, 2014b).

Potassium lactate has GRAS status in the U.S. and has been approved by FSIS to be used

to inhibit microbial growth on various meat and poultry products. Its use is approved up to 2%

for flavouring and up to 4.8% as an antimicrobial agent in meat and poultry products (FSIS,

2012). Potassium lactate is required to be included on the ingredients list as its common or usual

name (FSIS, 2015). In fish and seafood products, potassium lactate is approved as an ingredient

used in food with no limit other than good manufacturing process (FDA, 2012a). Therefore,

regulations in Canada and in the U.S. differ slightly, as the U.S. allows more potassium lactate in

foods and does not specify the maximum use of additives in fish and seafood products. While

potassium chloride is allowed in poultry products up to 3% in the U.S., there are no limitations

for its use in MPF in Canada.

2.2.4 High sodium intake and its complications in chronic kidney disease

Increased sodium intake in patients with CKD can more readily lead to volume retention

and increased blood pressure (Koomans et al, 1985). Hypertension is highly prevalent in CKD

and is estimated to be present in approximately 80-85% of patients (Whaley-Connell et al, 2008).

Hypertension is an important risk factor for cardiovascular disease, which is the leading cause of

death in patients with CKD (Sarnak & Levey, 2000). Furthermore, sodium restriction in dialysis

patients has been shown to improve control of hypertension, reduce hypotension during dialysis

treatment, and lessen the prescription of anti-hypertensive medication (Kayikcioglu et al, 2009;

Wright & Cavanaugh, 2010).

In patients with CKD who are not on dialysis, a high dietary sodium intake has been

associated with increased proteinuria (Verhave et al, 2004) and has also been shown to negate

the anti-proteinuric effects of angiotensin-converting enzyme inhibitor therapy (Heeg et al, 1989;

Slagman, 2011). Since proteinuria contributes to the progression of kidney disease, dietary

sodium restriction has been implicated in delaying the progression of kidney disease (Weir and

Fink, 2005).

19

There has been some recent controversy regarding the effects of a high sodium intake on

outcomes in the general population due to the fact that not all healthy individuals are salt-

sensitive. For example, Mente et al (2014) only observed substantial increases in blood pressure

in those individuals who consumed very high amounts of sodium (>6g Na/day), and also among

persons who had existing hypertension and were over the age of 55. Blood pressure effects were

modest in patients consuming a moderate sodium intake (3-5g Na/day) and not evident with

those consuming less than 3 grams sodium per day. However, in more advanced renal failure,

almost all patients are considered to have salt-sensitive blood pressure (Ritz et al, 2009).

Therefore, dietary sodium intake is an important consideration in the management on chronic

kidney disease.

2.2.4.1 Dietary sodium restriction

The 2012 KDIGO guidelines state that the benefits of restricting dietary sodium in the

pre-dialysis population “cannot be overemphasized” and recommend a sodium restriction of

<2000 mg per day, unless contraindicated. Similarly, K/DOQI clinical practice guidelines (2006)

recommend a sodium restriction of 2000 mg (85 mmol) per day in patients on hemodialysis in

order to optimize volume status and blood pressure.

These sodium intake recommendations are between the Adequate Intake (AI) of 1500

mg/day and Upper Limit (UL) of 2300 mg/day that was set for the general population (IOM,

2005). According to the 2004 Canadian Community Health Survey (CCHS 2.2), more than 90%

of adult Canadian men and 66% of adult Canadian women consume sodium amounts above the

UL of sodium per day (Barr, 2010). Similarly, approximately 90% of adults in the US consume

in excess of the recommendations (Cogswell et al, 2012).

2.2.4.1.1 Food sources of sodium

Approximately 75% of salt intake is derived from processed foods, whereas the natural

sodium content of food only contributes 10% of total intake (Mattes & Donnelly, 1991).

Moubarac et al (2014), looked at Canadian food expenditure in relation to its caloric content

from 1938 to 2011, and demonstrated that the consumption of ready-to-eat processed foods

increased from 29% to 62%. In Canada, CCHS 2.2 data revealed that the top sources of dietary

sodium were bread, processed meats and pasta dishes, which contributed 14%, 9% 6%,

respectively. The authors concluded that breads were the main source of dietary sodium due to

20

high consumption, whereas processed meats were consumed in lower quantities but were more

nutritionally dense in sodium (Fischer et al, 2009).

Much of sodium diet education for CKD patients focuses on limiting intake of canned,

pickled, and convenience items, as well as cured meat and fish products (ORN, 2013). In order to

achieve this target, renal dietitians suggest eating fresh, unprocessed versions of foods as these

are naturally lower in salt. Patients are also advised to read food labels and search for alternative

products with a lower content of sodium (Venegoor 2009).

2.3 Sodium reduction in Canada

The mean sodium intake of Canadians is about 3400mg per day, which is significantly

higher than the UL of 2300 mg sodium/day (Health Canada, 2010). There is substantial evidence

that associates a high dietary sodium intake with elevated blood pressure (MacGregor et al,

1989; Sacks et al, 2001; Kearney et al, 2005). Elevated blood pressure or hypertension, is

prevalent among Canadians and is considered a major modifiable risk factor for stroke,

cardiovascular disease (CVD) and renal disease (Barr, 2010). CVD is the second leading cause

of death in Canada (Statistics Canada, 2011) and it has been suggested by Penz et al. (2008) that

reducing dietary sodium intake can substantially reduce CVD events. Moreover, high dietary

sodium intake has been shown to be a risk factor for osteoporosis, stomach cancer and asthma

(DeWardener & MacGregor, 2002). It has been estimated that a decrease in average sodium

intake of 1,800 mg per day would result in Canadian health care savings of approximately 1.4 to

3 billion dollars per year (Penz et al, 2008).

2.3.1 Sodium Working Group

As a result of the high intake of sodium by Canadians and its association with disease,

Health Canada established a multi-stakeholder Sodium Working Group in 2007 to develop and

oversee strategies that would result in lowering the sodium intake of Canadians. The strategy

aimed to decrease the mean sodium intake of Canadians to the UL of 2300 mg per day by 2016,

with an ultimate goal to further lower mean dietary sodium intake to the AI of 1500 mg with the

majority of people below the UL (Health Canada, 2010).

In order to achieve this goal, four areas of recommendation were made: 1) improving

education and awareness about the sodium reduction strategy, 2) research pertaining to sodium

21

and sodium reduction, 3) a sodium monitoring and evaluation plan and 4) the voluntary

reduction of sodium in processed foods by various food manufacturers (Health Canada, 2010).

In order to decrease sodium content in the food supply, Health Canada collaborated with

the food industry to establish voluntary sodium reduction targets for each food category. When

establishing targets, there was careful consideration of the current sodium levels in food

categories, food safety, food quality, and feasibility of the targets. Although the Sodium Working

Group was disbanded in the 2011, Health Canada (2012a) published a document which provided

guidance to the food industry to reduce the levels of sodium in processed foods. The sodium

reduction benchmarks included three phased sodium reduction levels for the food industry to aim

to achieve by the end of 2016.

A qualitative survey was conducted with 55 Canadian food companies by Agriculture and

Agri-Food Canada (AAFC, 2013) which provided an update on sodium reduction efforts by the

food industry. Results indicated that most companies surveyed had a sodium reduction strategy

in place and had taken steps to reduce the level of sodium in their products. In addition, the Food

& Consumer Products of Canada determined that the introduction of reduced sodium products

rose 68% (FCPC, 2011). Health Canada is currently collecting dietary intake data through the

Canadian Community Health Survey. The results of this survey will be published in 2016 and

will further help track the progress in reducing dietary sodium intake.

2.3.2 Strategies to reduce sodium in meat, poultry and fish products

There are many key functional properties of salt and sodium-containing additives that

need to be taken into consideration when reducing sodium levels of foods. Salt, also known as

sodium chloride, is comprised of 40% sodium by weight and is the major contributor of sodium

in the diet (AAFC, 2013). In addition to being used for flavouring, salt and sodium act to help

with preservation, fermentation, microbial safety, leavening, protein binding, and the

development of texture and colour (AAFC, 2013).

Processed meat, poultry and fish products are significant sources of sodium in the diet.

In Canada, 19% of dietary sodium comes from processed meat, red-meat based dishes, poultry-

meat based dishes and fish and shellfish (Fischer et al, 2009). Salt has been used for centuries to

preserve MPF products as salt decreases water-activity, thus extending the shelf-life of the

22

product (Doyle & Glass, 2010). In meat products specifically, salt increases the water-binding

capacity by increasing binding properties of proteins to improve texture (Desmond, 2006). It

solubilizes muscle protein which allows gel formation and optimum texture in processed meat

products that are emulsified (i.e. frankfurters, bologna). Thus, reducing the amount of salt can

have major implications in the flavor, texture and shelf-stability of MPF products. A recent study

by Miller et al (2015) demonstrated that sodium-reduced ready-to-eat meat products in Canada

contained higher bacterial diversity than regular counterparts.

Some of the strategies food manufacturers may use to reduce the sodium content of their

products include reducing sodium content gradually, replacing salt with other chloride salts or

using non-chloride based salts (Verma & Banerjee, 2012). A salt reduction of 10-25% might be

accomplished without having unfavorable effects on palatability of the product (CTAC, 2009). In

addition, it is beneficial for the reduction of salt to happen slowly so that it does not affect

consumer acceptability of the product (Desmond, 2006). Over time, it has been shown that

consumers are able to become more sensitive to a salty taste and adapt to lower sodium levels

(Bertino et al, 1982). The most frequently used chloride-based salt substitute is potassium

chloride, although magnesium chloride and calcium chloride have also been used. The most

common non-chloride based salt substitute is phosphate-based additives (Verma and Banerjee,

2012).

2.3.2.1 Use of potassium additives in sodium reduction of foods

Potassium chloride provides a salty flavour which allows for products to have a similar

perceived saltiness as salt, but that can be achieved with a lower sodium content (Desmond,

2006). It has been estimated that potassium chloride can replace up to about 30% of sodium

chloride in many foods (Doyle & Glass, 2010). The use of potassium chloride is limited as it

produces a bitter and metallic after taste, therefore it is often mixed with sodium chloride to form

a blend (Verma & Banerjee, 2012). Bitter blockers or taste enhancers, such as tricalcium

phosphate, can be used to mask the unpleasant flavours produced by potassium chloride (CTAC,

2009).

As mentioned previously, the DASH diet indicated that a diet lower in sodium and higher

in potassium has a blood pressure lowering effect (Sacks et al, 2001). Therefore, the addition of

potassium salts to foods can be perceived as being advantageous to food manufacturers and the

23

general population. While the U.S. Dietary Guidelines (2005) mentioned that salt substitutes can

be harmful for individuals with certain medical conditions, the guidelines also stated that a diet

rich in potassium blunts the effect of salt on blood pressure and increased dietary intake of

potassium may especially benefit certain populations who have a high prevalence of

hypertension. Health Canada’s sodium reduction strategy (2010) suggested that it would be

beneficial for food manufacturers to first reduce the use of salt, and use salt substitutes when it is

necessary.

Since sodium plays a key role in preservation and microbial safety, when it is removed

from meat products it can pose a food safety concern and reduce the shelf-life of the product.

Lactates, such as potassium lactate, are effective in controlling microbial growth in meat and

poultry products (Health Canada, 2012b) and can enhance saltiness (Dotsch et al, 2009). This

effect is further enhanced with the combination of potassium lactate and sodium diacetate which

act synergistically and can reduce sodium chloride levels by 40% in packaged cooked meats

(Doyle & Glass, 2010). Additionally, Gou et al. (1995) demonstrated that 40% of sodium

chloride could be substituted using a potassium chloride and potassium lactate mix, in dry cured

pork loins. Potassium lactate is therefore an effective sodium replacement that can extend the

shelf-life of meat and poultry products.

2.3.2.2 Use of phosphorus additives in sodium reduction of foods

Several studies have shown that phosphates, such as sodium polyphosphate, are useful to

help lower the sodium content of meat products as they increase the water holding capacity and

improve cooking yield (Verma & Banerjee, 2012). Phosphorus additives and salt act

synergistically, which reduces the requirement of salt from 3-3.5% to 1.4-1.8% (Shults et al,

1972). Phosphorus additives are most commonly found in cured pork products (ham, bacon),

pulverized meats (frankfurters, bologna), precooked breakfast sausages, deli meats, breaded

chicken products, and poultry that has been enhanced or seasoned (Lampila, 2013). Sodium

phosphate is the second highest source of sodium in meats, after sodium chloride, and contains

approximately 30% sodium (Ruusunen et al, 2002).

In meat products, solutions containing sodium phosphates, potassium salts (U.S. only),

and/or spices can be injected into the fresh meat or poultry products. These products are as

labelled “seasoned” in Canada or “enhanced” in the United States (CFIA, 2013; FSIS 2014).

24

Meat and poultry are often seasoned to help maintain tissue integrity which results in a more

moist and tender product, even when cooked (Murphy-Gutekunst & Uribarri 2003). In addition,

the injection of sodium phosphates reduces purge, which is the liquid that is released from raw

meat as it ages, and can be perceived as being undesirable by consumers (Murphy-Gutekunst &

Uribarri, 2005).

In fish and seafood, phosphorus additives help with the retention of moisture and flavor,

the prevention of lipid oxidation, protection from freezer damage, prevention of struvite in

canned seafood and preservation (Lampila, 1992). Sodium tripolyphosphate is also used as a

processing aid to mechanically peel shrimp from its shell, by dipping shrimp in a 3-5%

phosphate solution for 5 minutes prior to cooking it (Lampila, 2013). Similar to meat and poultry

products, phosphates act synergistically with sodium phosphate allowing for less use of salt in

the final product (Lampila, 1992). Fish and shellfish only contribute 2% of dietary sodium intake

of Canadians (Fischer et al, 2009), therefore the food industry may focus their sodium reduction

efforts on food groups that are higher contributors of sodium intake.

Potassium phosphates, such as potassium tripolyphosphate and tetrapotassium

pyrophosphate, are helpful for further reductions of sodium in meat products. They provide the

many favourable effects of phosphate additives and also provide a salty flavor due to the

potassium. In addition, they are effective in terms of water binding and gelation (Verma &

Banerjee, 2012). The extent of sodium reduction depends on the type of potassium phosphates

used and their sodium content (Ruusunen, 2002). In 2014, tripotassium phosphate, potassium

tripolyphosphate and sodium potassium hexametaphosphate were approved for use in Canada as

sodium analogues in the sodium reduction of foods (Health Canada, 2014). Some of the

conditions in which they were approved for use include reducing processing losses in fish and

seafood products, acting as a curing agent in meat and poultry products, and reducing fluid losses

during the thawing of fish.

25

3.0 Rationale and Objectives

Approximately three million Canadians either have chronic kidney disease (CKD), or are

at risk of developing CKD (Arora et al, 2013). As kidney function decreases, the body is unable

to excrete sufficient amounts of phosphorus and potassium through the urine, which can lead to

hyperphosphatemia and hyperkalemia (Kopple & Massry 2004).

Hyperphosphatemia is associated with an increased risk of death in patients in later stages

of CKD and those receiving dialysis (Block et al, 1998; Kestenbaum et al, 2005; Palmer et al,

2011). Guidelines recommend patients with hyperphosphatemia restrict their dietary intake of

phosphorus to between 800 and 1000 mg per day (K/DOQI, 2003). Phosphorus additives can

contribute up to 1000 mg phosphorus per day to the average American diet making adherence to

a low phosphorus diet challenging (Bell et al, 1977; Uribarri & Calvo, 2003).

Hyperkalemia is common in patients with chronic kidney disease and can lead to

increased risk of mortality, due to its effect on cardiac conductivity (Putcha & Allon, 2007).

Potassium chloride is the most frequently used salt substitute due to its salty taste and functional

effects (CTAC, 2009). The use of potassium salts has been associated with toxicity in patients

with CKD (Ray et al, 1999; Doorenbos & Vermeij, 2003; John et al, 2011).

In Canada, it is not mandatory to report phosphorus or potassium content on food labels,

unless there is a related nutrient claim. Therefore, it is difficult to accurately estimate the

potassium and phosphorus content of foods with additives. Studies in the United States and

Europe have shown that the addition of phosphorus and potassium additives significantly

increases the phosphorus and potassium content of the food item (Sherman & Mehta, 2009a;

Benini et al, 2011). To our knowledge, no such studies have taken place in Canada. Accurately

estimating the phosphorus and potassium content of foods is necessary to help CKD patients

choose appropriate foods and adhere with their diet restrictions. This in turn may help prevent

hyperphosphatemia, hyperkalemia and their respective adverse health effects.

In 2007, Health Canada formed the Sodium Working Group to develop, implement and

oversee a strategy to lower the sodium content of Canadians’ diets to within the recommended

range. The strategy included a voluntary reduction of sodium in processed foods by

manufacturers. The food industry suggested methods to reduce sodium content of foods without

26

compromising taste and food safety. Some of these suggestions include the addition of potassium

salts and phosphate-containing additives, especially in processed meats (CTAC, 2009). This

creates a concern among people suffering with ESRD, in which a diet high in protein (1.2

g/kg/day) and low in sodium (less than 85 mmol or 2000 mg per day) is recommended (KDOQI,

2000; KDIGO, 2012). Patients with ESRD are educated to increase their intake of protein from

sources such as meat, poultry and fish, as well as choose lower sodium food products, which

may unintentionally lead to an increased intake of phosphorus and potassium (Venegoor, 2009).

The overall aims of our study was to gain knowledge of the actual content of total

phosphorus and potassium content in commonly consumed meat, poultry and fish products,

among the CKD population, and to determine if the sodium reduction of processed foods is

associated with increased amounts of phosphorus and potassium additives.

We hypothesized that MPF foods containing phosphorus and potassium additives will

contain higher amounts of phosphorus and potassium compared to foods without these additives.

In addition, we hypothesized that sodium reduced foods will contain higher amounts of

phosphorus and potassium compared to its original non-sodium reduced counterpart. In order to

test our hypotheses we conducted three studies:

Study 1: Commonly consumed meat, poultry and fish (MPF) products among patients with

End-Stage Renal Disease at a Tertiary Care Teaching Hospital in Toronto, Canada: Food

Questionnaire. The primary objective of this study was to identify the most commonly

consumed MPF products among patients receiving dialysis. Our secondary objective was to

describe the patient’s purchasing and food preparation behaviours related to MPF products. The

results helped to guide the selection of foods for study 2 (food analysis).

Study 2: Phosphorus and potassium content of commonly consumed meat, poultry and fish

products among patients with CKD. The aim of this study was to gain knowledge of the actual

content of added phosphorus and potassium of commonly consumed meat, poultry and fish

products, among the CKD population. Specific objectives were:

1) To determine whether and to what extent the chemically analyzed phosphorus,

potassium, sodium and protein contents differ among commonly consumed MPF

products with and without additives listed on their ingredient list.

27

2) To determine whether and to what extent the chemically analyzed phosphorus,

potassium, sodium and protein contents differ among poultry products with and without

the term ‘seasoned’ on the product label.

Study 3: Do Sodium Reduced Meat and Poultry Products Contain a Significant Amount of

Potassium and Phosphorus from Additives? The objective of this study was to determine

whether and to what extent the reduction of sodium in meat and poultry products is associated

with higher amounts of potassium and phosphorus from food additives.

28

4.0 Commonly consumed meat, poultry and fish products among patients with

End-Stage Renal Disease at a Tertiary Care Teaching Hospital in Toronto,

Canada: Food Questionnaire

4.1 Introduction

Hyperphosphatemia is a common condition in chronic kidney disease (CKD) and is

associated with an increased risk of mortality (Block et al, 1998; Kestenbaum et al, 2005;

Palmer, et al 2011). Hence, the prevention and correction of hyperphosphatemia is a key aspect

in the management of CKD. Methods to lower serum phosphorus levels include the use of

phosphate binding medication, dialysis therapy and restriction of dietary phosphorus intake.

Approximately 20-30% of the dietary phosphate intake comes from animal protein such as, meat,

fish, poultry, milk and eggs (Calvo & Park, 1996), however, patients requiring dialysis are

advised to increase their intake of these high biological value protein sources.

There is concern that additives containing phosphorus are increasingly being used to

enhance the properties of meat, poultry and fish (MPF) products (Uribarri & Calvo, 2003).

Several studies have compared the nutrient content of MPF products that contained additives

with additive-free products. These studies showed the phosphorus content increased by

approximately 30-60% in foods containing phosphorus additives. However, the selection of

foods analyzed in these studies was often done arbitrarily (Sherman & Mehta, 2009ab; Sullivan

et al, 2007; Benini et al, 2011).

Current practice is to recommend fresh MPF products, as these are lower in sodium than

processed MPF (Vennegoor, 2009). However, there is no literature to our knowledge that

outlines the main sources of MPF that patients with CKD are purchasing and consuming. Studies

that did investigate the dietary intake of patients with ESRD did not report on the details, such as

specific types of MPF foods that were purchased (Fassett et al, 2007, Khoueiry et al, 2011;

Kalantar-Zadeh et al, 2002). Furthermore, studies describing types of foods consumed in the

general population may not be generalizable to the hemodialysis population due to the numerous

dietary restrictions that alter food intake patterns from those of healthy individuals (Kalantar-

Zadeh et al, 2002).

29

The primary objective of this study was to identify the most commonly consumed MPF

products among patients receiving dialysis. Our secondary objective was to describe the patient’s

purchasing and food preparation behaviours related to MPF products.

The results of this project will provide guidance for the evidence-based selection of foods

for the next phase of our study, in which we will analyze and compare the nutrient content of

MPF products with and without food additives. The results will ensure the MPF items chosen are

relevant to the dialysis patient population in a tertiary care teaching hospital in Toronto, Canada.

4.2 Materials and Methods

4.2.1 Design

This was a cross-sectional survey that involved hemodialysis and peritoneal dialysis

patients at St. Michael’s Hospital in Toronto, Canada. The food frequency questionnaire was

developed specifically for the purposes of this study and underwent a face validation process

with patients and health care practitioners. Ethics approval was obtained from the Research

Ethics Boards at both St. Michael’s Hospital and the University of Toronto. Informed written

consent was obtained from each participant.

4.2.2 Patient questionnaire development

Questions pertaining to the consumption of MPF products were extracted from the

Canadian Diet History Questionnaire II (DHQ II), adapted from the National Institute of Health

DHQ II(Csizmadi et al, 2007). The DHQ is a validated food frequency questionnaire with a

correlation coefficient of 0.48 between energy intake from DHQ and estimated truth by four 24-

hour recalls (Subar et al, 2001). Meat products included beef and pork based products. Poultry

products included chicken and turkey based products. Fish products included white fish,

dark/pink fish, and shellfish products. Food frequency questions pertaining to both processed and

unprocessed MPF were included as part of the patient questionnaire. The self-reported adherence

to renal restriction questions were extracted from the Block Dialysis I Food Frequency

Questionnaire (Kalantar-Zadeh et al, 2011). The questionnaire was designed to be a self-

administered, however, assistance from a research assistant was provided as needed.

The questionnaire consists of 40 questions within four principal domains (Appendix A);

30

1) Frequency, types, and brands of MPF products consumed (23 questions).

2) Purchasing and preparation behaviours (10 questions)

3) Self-reported adherence to renal restrictions (2 questions)

4) Demographic and clinical data (5 questions)

4.2.3 Face validation of patient questionnaire

The questionnaire was tested for face validity among a group of nephrology health care

professionals (n=6) and ESRD patients (n=6). Health care professionals who provided verbal

consent to participate in the face validation process were sent an e-mail by the principal

investigator outlining the study and face validation process. They were asked to provide

feedback on the readability, content, and appropriateness of questions.

In addition, patients receiving hemodialysis or peritoneal dialysis at St. Michael’s

hospital were approached by a research assistant using a recruitment pre-amble for face

validation (Appendix B). Following their consent, patients were asked to review the

questionnaire and provide comments directly on the questionnaire with specific regards to the

readability, clarity and appropriateness of the questions.

The questionnaire was revised based on the comments obtained from the face validation

exercise to ensure that questions were appropriate, as well as clear and easy to understand.

4.2.4 Eligibility criteria

Patients with ESRD receiving hemodialysis or peritoneal dialysis at St. Michael’s

Hospital who were able to verbally communicate in English or who had a primary household

shopper who was able to verbally communicate in English were eligible for inclusion into the

study.

Patients were ineligible if they and/or their primary caregiver did not cook at home and/or

were unable to grocery shop (i.e. if they lived in a nursing home or received meals on wheels),

were unable to ingest regular solid food, were vegetarian, were receiving palliative care, or had a

major psychiatric disorder or severe dementia.

31

4.2.5 Recruitment methods

All patients receiving in-centre hemodialysis or peritoneal dialysis at St. Michael’s

Hospital were identified and screened for eligibility using the patient census. Eligible

hemodialysis patients were initially approached by their nurse practitioner, while eligible

peritoneal dialysis patients were approached by the dietitian in the peritoneal dialysis clinic. A

scripted pre-amble was used to introduce the study (Appendix C). If the patient expressed

interest in enrolling in the study, they were then approached by a research assistant who was not

within the patient’s circle of care to obtain informed consent (Appendix D).

4.2.6 Questionnaire administration and data collection

The questionnaire was administered to participants by a research assistant during a

routine clinic or dialysis visit. The participant had the choice to complete the questionnaire at the

time of administration, or take it home and return it at their next hospital visit. The research

assistant reviewed completed questionnaires, and clarified any unclear answers with the

participant. Participants were encouraged to answer all the questions but were made aware that it

was not mandatory.

Questions were designed to be self-explanatory. However, participants were encouraged

to ask research assistants for clarification of any questions, or assistance in completing the

questionnaire. The questionnaire took approximately 30 to 45 minutes to complete.

Additional data was collected from the participant’s chart by a trained research individual

using a data collection form (Appendix E). This data included age, sex, dialysis vintage,

significant co-morbidities (diabetes, hypertension and heart failure), anthropometric data (dry

weight or body weight measured post-dialysis, height, BMI) and the most recent biochemical

data (pre-dialysis urea, albumin, phosphorus, calcium, potassium, and percentage reduction in

urea).

4.2.7 Data analysis

This was a sample of convenience as we aimed to screen all patients attending dialysis

during the study recruitment period for eligibility and inclusion in the study (sample pool size of

226). Continuous variables were summarized using means, medians, standard deviations and,

32

minimums and maximums, whereas categorical variables were described using frequencies and

percentages.

Consumption of MPF products was expressed as grams per month. The portion sizes

listed in the questionnaire (from Canadian DHQ II) correspond to gram weights that were sex-

specific, based on actual consumption of foods reported from dietary intake recall data from

Statistics Canada’s Community Health Survey (CCHS 2.2). Consumption per month was

estimated by calculating the product of frequency of consumption (times per month) and portion

size usually eaten (grams). The MPF products were ranked from highest to lowest according to

the estimated mean weight consumption per month. The highest mean weight consumed per

month reflected the most commonly consumed type of MPF.

In addition, servings were defined using the standard food serving sizes from Health

Canada’s Nutrient Value of Some Common Foods (2008). Weight consumption per month was

divided by the standard food serving size in order to determine serving consumption per month

for each type of MPF.

Results 4.4

4.4.1 Participant recruitment

Over the period of July to September 2013, 196 hemodialysis and 30 peritoneal dialysis

patients attended SMH in-centre hemodialysis unit and peritoneal dialysis clinic and were

screened for inclusion in the study. Of the patients screened, 122 hemodialysis and 26 peritoneal

dialysis patients met eligibility criteria. The main reasons for exclusion from the study were: did

not cook at home (49%) and language barrier (31%). Sixty-seven participants provided consent

and completed the questionnaire (Figure 4.1).

4.4.2 Demographic and clinical characteristics of participants

Characteristics of participants are summarized in Table 4.1. Sixty-four percent of

participants were male and the majority (76%) received conventional hemodialysis. The mean

(standard deviation) BMI was 26 (5) kg/m2 and laboratory values were within acceptable ranges

for patients receiving dialysis. The majority of patients (57%) had received post-secondary

education.

33

4.4.3 Commonly consumed meat, fish and poultry products

Ranked sources of MPF products based on weight (g) consumption per month are

summarized in Table 4.2. The top five most commonly consumed types of MPF (based on

estimated product weight) among ESRD patients at St. Michael’s Hospital were unbreaded

chicken, ground beef, steak, white fish and beef burgers.

Participants generally chose fresh options versus packaged types of each MPF. There

were very few participants who commented on brands of MPF purchased, however, those who

did, mentioned popular national brands most often (i.e. Maple Leaf®, Schneider’s

®, and Clover

Leaf®).

Ranked sources of MPF based on number of servings consumed per month by patients

are summarized in Table 4.3. The most commonly consumed types of MPF (based on number of

servings) were unbreaded chicken, ground beef, shrimp, steak and bacon.

4.4.4 Purchasing and preparation behaviours

Purchasing and preparation behaviours are described in the Table 4.4. The most common

grocery stores that participants shopped at were No Frills (60%), Metro (52%) and Loblaws

(39%). Either the participant or their spouse completed the grocery shopping and cooking at

home most often. Fifty-six percent of participants ate a meal outside of their home at least one

time per week. Participants reported checking the sodium, potassium and fat content of foods

most often when examining the Nutrition Facts table (78%, 54% and 51%, respectively). Forty

percent of participants looked for phosphorus in the ingredients list, while 48% looked for

potassium. Eighty-five percent of patients reported never using a salt substitute. Forty-five

percent of participants reported choosing a sodium-free or reduced sodium product most of the

time.

4.4.5 Self-reported adherence to renal diet restrictions

Self-reported adherence to renal restrictions is described in Table 4.4. The majority of

participants answered that they try to adhere to low phosphorus diet (79%), however, 42%

admitted that they don’t always follow it. Similarly, 81% of patients reported trying to follow a

low potassium diet, but 24% admit they don’t always adhere to their diet.

34

Figure 4.1 Flow diagram of subject recruitment and study completion

196 screened in-centre hemodialysis

patients at St. Michaels Hospital

(July-Sept 2013)

74 Ineligibile patients

38 Did not cook at home

24 Language barrier

4 Unable to ingest solid foods

2 Major psychiatric disorder

1 Vegetarian

1 Severe dementia

4 Transferred programs

70 Declined

122 met eligibility criteria

52 Enrolled

30 screened peritoneal dialysis patients

at St. Michaels Hospital

(July-Sept 2013)

4 Ineligibile patients

2 Major psychiatric disorder

1 Vegetarian

1 Language Barrier

26 met eligibility criteria

15 Enrolled 11 Declined

67 Enrolled

67 completed the questionnaire

35

Table 4.1 Demographic and clinical characteristics of participants (n=67)

Characteristics Results

Mean (SD) n (%)

Age, years 59 (15)

Sex

Male

Female

43 (64)

24 (36)

Dialysis Vintage†, years 4 (5)

Mode of Dialysis

Conventional (3x/wk) Hemodialysis

Peritoneal Dialysis

Short Daily Hemodialysis

51 (76)

15 (22)

1 (2)

Co-Morbidities

Diabetes

Hypertension

Cardiovascular Disease

29 (43)

54 (81)

17 (25)

Dry Weight††

, kg 73 (21)

Height, cm 165 (12)

BMI, kg/m2 26 (5)

Albumin, g/L 39 (3)

Phosphorus, mmol/L 1.6 (0.5)

Calcium, mmol/L 2.2 (0.2)

Potassium, mmol/L 4.6 (0.7)

Urea, mmol/L 23 (7)

PRU*, mmol/L 78 (7)

Type of home

House

Apartment

Other

26 (39)

38 (57)

3 (4)

# People in Household

No one else

One other

Two others

Three others

4 or more others

10 (15)

28 (42)

13 (19)

11 (16)

5 (8)

Education

Elementary School

Some high school

High school diploma

Some university/college

University/college degree

Graduate

None

3 (5)

7 (10)

18 (27)

10 (15)

20 (30)

8 (12)

1 (2)

Ethnicity**

Aboriginal

African/Black

8 (12)

8 (12)

36

Caribbean

East Asian

Caucasian / White

Middle Eastern

South Asian

South-East Asian

9 (13)

4 (6)

29 (43)

2 (3)

11 (16)

5 (7)

Annual Income

> $100,000

$80,000 -$100,000

$60,000 - $80,000

$40,000 - $60,000

$20,000 - $40,000

< $20,000

5 (8)

3 (5)

7 (10)

12 (18)

18 (27)

2 (3) *measured in patients receiving hemodialysis only (n=51)

**Indicates a questions where the participant can choose more than one answer (check all that apply) †Dialysis Vintage defined as the length of time on dialysis in years

††Dry weight defined as the established amount of body mass (weight) without extra fluid (water)

37

Table 4.2 Ranked Consumption of meat, poultry and fish products based on estimated

weight (g) consumption per month by ESRD patients (n=67)

Rank Source of

MPF

Consumption,

Total grams /

month

Mean (SD)

Serving

size*

(grams)

Zero

consumption

N (%)

Types of MPF consumed**

N (%)

1 Unbreaded

Chicken 888 (1158) 75 2 (3)

Fresh, packaged

Fresh, butcher

Frozen

Rotisserie

I don’t know

Other

45 (67)

22 (33)

10 (15)

14 (21)

1 (1)

2 (3)

2 Ground

Beef 449 (861) 75 13 (19)

Fresh

Frozen

Other

46 (69)

7 (10)

2 (3)

3 Steak 365 (639) 75 14 (21)

Fresh, packaged

Fresh, butcher

Frozen

I don’t know

28 (42)

32 (48)

1 (1)

1 (1)

4 White Fish 281 (635) 75 27 (40)

Fresh, packaged

Fresh, seafood counter

Frozen

Other

11 (16)

21 (31)

12 (18)

3 (4)

5 Burger 243 (315) 75 18 (27)

Fresh, homemade

Frozen

I don’t know

Other

35 (52)

15 (22)

1 (1)

3 (4)

6 Beef 203 (294) 75 20 (30)

Fresh, packaged

Fresh, butcher

Frozen

23 (34)

29 (43)

1 (1)

7 Cold Cuts 182 (606) 56

(2 slices) 32 (48)

Pre-packaged

Deli Counter

Other

14 (21)

23 (34)

3 (4)

8 Canned

Tuna 169 (282) 75 22 (33) n/a n/a

9 Dark Fish 169 (293) 75 31 (46)

Fresh, packaged

Fresh, deli counter

Frozen

Other

15 (22)

5 (7)

3 (4)

1 (1)

10 Pork 164 (313) 75 28 (42)

Fresh, packaged

Fresh, meat counter

Frozen

23 (34)

17 (25)

2 (3)

11 Shrimp 157 (363) 30

(6 medium) 28 (42)

Fresh, seafood counter

Frozen, unbreaded

Frozen, breaded

Other

14 (21)

29 (43)

2 (3)

3 (4)

12 Poultry

Cold Cuts 147 (235) 56 30 (45)

Pre-packaged

Deli Counter

17 (25)

24 (36)

13 Hot Dog 116 (401) 38 (1) 30 (45) Fresh, packaged

Fresh, deli counter

26 (39)

5 (7)

38

*Serving sizes were determined by Health Canada’s Nutrient Value of Some Common Foods, 2008

**Indicates a questions where the participant can choose more than one answer (check all that apply)

Frozen

I don’t know

Other

3 (4)

1 (1)

4 (6)

14 Breaded

Chicken 116 (280) 75 35 (52)*

Fresh, breaded

Frozen

Other

14 (21)

17 (25)

6 (9)

15 Sausage 115 (486) 75 40 (60)*

Fresh, packaged

Fresh, deli counter

Other

16 (24)

7 (10)

1 (1)

16 Bacon 109 (434) 24

(3 slices) 36 (54)*

Fresh, packaged

Fresh, meat counter

I don’t know

Other

28 (42)

4 (6)

1 (1)

4 (6)

17 Deli Ham 103 (202) 56

(2 slices) 33 (49)

Pre-packaged

Deli Counter

13 (19)

24 (36)

18 Canned

Salmon 82 (275) 75 41 (61)* n/a n/a

19 Breaded

Fish 81 (260) 75 39 (58)*

Fresh, battered

Frozen

7 (10)

21 (31)

20 Ham 68 (448) 75 57 (85)*

Packaged, cooked

Meat Counter

Other

5 (7)

4 (6)

1 (1)

21 Turkey 57 (96) 75 41 (61)*

Fresh, packaged

Fresh, butcher

Frozen

Other

13 (19)

6 (9)

6 (9)

3 (4)

22 Ribs 53 (95) 75 35 (52)*

Fresh, packaged

Fresh, meat counter

Frozen

Other

11 (16)

16(24)

5 (7)

3 (3)

23 Shellfish 31 (840) 75 45 (67)*

Fresh, seafood counter

Frozen

Other

13 (19)

8 (12)

1 (1)

39

Table 4.3 Ranked sources of meat, poultry and fish Products, based on number of servings

consumed per month by ESRD patients

Rank Source of MPF Serving size

(g)

Total number of servings

consumed per month

Mean (SD)

Zero

consumption

N (%)

1 Unbreaded Chicken 75 11.8 (15.4) 2 (3)

2 Ground Beef 75 8.0 (15.4) 13 (19)

3 Shrimp 30 (6 medium) 5.2 (12.1) 28 (42)

4 Steak 75 4.9 (8.5) 14 (21)

5 Bacon 24 (3 slices) 4.6 (18.1) 36 (54)*

6 White Fish 75 3.8 (8.5) 27 (40)

7 Cold Cuts 56 (2 slices) 3.3 (10.8) 32 (48)

8 Burger 75 3.2 (4.2) 18 (27)

9 Hot Dog 38 (1) 3.1 (10.6) 30 (45)

10 Beef 75 2.7 (3.9) 20 (30)

11 Poultry Cold Cuts 56 2.6 (4.2) 30 (45)

12 Canned Tuna 75 2.3 (3.8) 22 (33)

13 Dark Fish 75 2.2 (3.9) 31 (46)

14 Pork 75 2.2 (4.2) 28 (42)

15 Deli Ham 56 (2 slices) 1.8 (3.6) 33 (49)

16 Breaded Chicken 75 1.6 (3.7) 35 (52)*

17 Sausage 75 1.5 (6.5) 40 (60)*

18 Canned Salmon 75 1.1 (3.7) 41 (61)*

19 Breaded Fish 75 1.1 (3.5) 39 (58)*

20 Ham 75 0.9 (6.0) 57 (85)*

21 Turkey 75 0.8 (1.3) 41 (61)*

22 Shellfish 75 0.4 (1.1) 45 (67)*

23 Ribs 75 0.1 (1.3) 35 (52)*

* Greater than 50% (n=34) of patients do not consume source of MPF

40

Table 4.4 Purchasing, food preparation behaviours and self-reported adherence to renal

diet restrictions

Question Results n (%)

Purchasing and Preparation Behaviours

*At which grocery store(s) do

you shop?

Sobey’s 16 (24)

Metro 35 (52)

No Frills 40 (60)

Loblaws 26 (39)

Great Canadian Superstore 8 (12)

Costco 15 (22)

Other 26 (39)

*Who does the grocery shopping

at home?

You 37 (55)

Spouse 28 (42)

Children 9 (13)

Caregiver 3 (5)

Other 2 (3)

*Who does the cooking at

home?

You 40 (60)

Spouse 23 (34)

Children 8 (12)

Caregiver 5 (8)

Other 4 (6)

During the past month, how

often did you eat a meal outside

of the home (includes

restaurants, fast food, coffee

shops)?

More than once a day 4 (6)

Once a day 3 (5)

4-5 times per week 7 (10)

2-4 times per week 16 (24)

1-2 times per week

2-3 times per month

10 (15)

6 (9)

Once per month 12 (18)

Less than once per month 9 (13)

*If you read the Nutrition Facts

table (see picture) to find out

about the nutritional content of

the food, what do you usually

look for?

Calories 21 (31)

Sodium 52 (78)

Fat 34 (51)

Protein 15 (22)

Phosphorus 23 (37)

Potassium 36 (54)

Carbohydrate 10 (15)

Sugar 28 (42)

Fiber 12 (18)

I don’t read the Nutrition Facts Table 6 (9)

I don’t know 2 (3)

Do you use the salt substitute,

called NoSalt©, NuSalt© or

HalfSalt©, when you cook?

I often use a salt substitute 3 (5)

I sometimes use a salt substitute 7 (10)

I never use a salt substitute 57 (85)

I don’t know 0 (0)

*If you read the list of I don’t read the ingredient list 23 (34)

41

ingredients of the food you buy,

what do you usually look for?

Ingredients with the word “phosphorus” or letters

“phos”

27 (40)

Ingredients with the word “potassium” 32 (48)

Other 17 (25)

How often do you try to choose

foods that say “Sodium-Free” or

“No Sodium” or “No Added

Salt” on the food package?

Most of the time 30 (45)

Some of the time 19 (28)

Never 14 (21)

I don’t know 4 (6)

How often do you try to choose

foods that say “Reduced in

Sodium” or “25% Less Sodium”

or “Lightly Salted” or “Lower

in Sodium” on the package?

Most of the time 30 (45)

Some of the time 18 (27)

Never 17 (25)

I don’t know 2 (3)

Self-reported adherence to renal restrictions

If you are asked to follow a low

phosphorus diet, do you think

you are following it?

I am not asked to follow a low phosphorus diet

7 (10)

I try to follow a low phosphorus diet and I usually

do

25 (37)

I try to follow a low phosphorus diet, but I don’t

always follow it

28 (42)

I don’t follow a low phosphorus diet 3 (5)

I don’t know what a low phosphorus diet is 4 (6)

If you are asked to follow a low

potassium diet, do you think you

are following it?

I am not asked to follow a low potassium diet

6 (9)

I try to follow a low potassium diet and I usually do 38 (57)

I try to follow a low potassium diet, but I don’t

always follow it

16 (24)

I don’t follow a low potassium diet 6 (9)

I don’t know what a low potassium diet is 1 (1) * Indicates a question where the participant can choose more than one answer (check all that apply)

42

Table 4.5 Characteristics of study patients receiving hemodialysis as compared with the

Canadian Institute for Health Information data

Study Participants

(2013)

SMH CIHI

(2012)

Province

CIHI (2012)

Canada CIHI

(2012)

n = 52 n = 248 n = 8,160 n = 14, 632

Age, Mean (SD) 59.4 (13.7) 60 (14) 65.2 (15.3) 64.9(15.4)

Male, % 67.3 59.1 58.4 58.7

Caucasian Race, % 42 43 65 64

Diabetes, % 38.5 44.0 48.3 47.4

BMI, Mean, kg/m2 26.1 26.5 28.5 28.6

Phosphorus,

Mean (SD), mmol/L

1.6 (0.5) 1.5 (0.5) 1.6 (0.5) 1.7 (0.5)

Calcium,

Mean (SD), mmol/L

2.2 (0.2) 2.3 (0.2) 2.4 (0.3) 2.3 (0.2)

Albumin,

Mean (SD), g/L

39.5 (3.1) 38.8 (4.2) 36.2 (5.2) 35.6 (5.2)

Table 4.6 Characteristics of study patients receiving peritoneal dialysis as compared with

the Canadian Institute for Health Information data

Study Participants

(2013)

SMH CIHI

(2012)

Province

CIHI (2012)

Canada CIHI

(2012)

n = 15 n = 52 n = 1,538 n = 3,128

Age, Mean (SD) 59.7 (17.7) 66.1 (15.6) 63.6 (15.0) 62.4 (14.9)

Male, % 53.3 61.5 58.2 58.5

Caucasian Race, % 46.7 40.4 60.5 61.2

Diabetes, % 40.0 51.9 44.7 42.1

BMI, Mean, kg/m2 27.6 25.1 27.4 27.6

Phosphorus,

Mean (SD), mmol/L

1.7 (0.6) 1.5 (0.5) 1.6 (0.5) 1.7 (0.5)

Calcium,

Mean (SD), mmol/L

2.2 (0.2) 2.4 (0.2) 2.5 (0.2) 2.4 (0.2)

Albumin,

Mean (SD), g/L

36.7 (3.8) 36.4 (4.5) 34.0 (5.5) 33.6 (5.6)

*Source: Canadian Institute for Health Information. Canadian Organ Replacement Register (2014):

Centre-Specific Clinical Measures Report of Dialysis Patients in Canada 2010 to 2012

Abbreviations: SMH = St. Michael’s Hospital; CIHI = Canadian Institute for Health Information;

BMI = Body Mass Index

43

4.5 Discussion

The results of the dietary survey indicate that unbreaded chicken is the most commonly

consumed source of MPF among patients with ESRD at St. Michael’s Hospital. Ground beef,

steak, white fish and burgers were also among the most common MPF foods consumed by

weight. These results are in line with Agriculture Canada data (2013) which demonstrates

chicken is the most commonly consumed animal protein per capita in Canada. Similarly,

NHANES 2007-2010 data showed that poultry and beef were the top sources of dietary animal

protein (Pasiakos et al, 2015). The majority of participants tended to choose fresh versions of

MPF, which is recommended by their dietitian as part of a renal diet. This study was the first

Canadian study to describe the most frequently consumed types of MPF products among patients

with ESRD.

We also examined MPF consumption based on the number of servings consumed per

month as the typical serving size consumed varies per type of MPF. For example, the standard

serving size of solid cuts of meat and poultry is 75g; however, the standard serving for deli meat

and bacon is only 56g and 24g, respectively. While five out of the top eight foods were identical

to those shown by consumption by weight; shrimp, bacon and cold cuts were considered

commonly consumed MPF based on serving size. Bacon and cold cuts are not a part of a low

sodium diet indicating that patients are often non-adherent to low sodium diet restrictions. A

recent study among CKD patients in England, demonstrated that 87% of patients reported

consumption of canned or processed meats at least once per week (Nerbass et al, 2014).

Participants shopped at No Frills, Loblaws and Metro most often, which are among the

top grocery store chains in Canada (Mintel, 2009; Schermel et al, 2013). Twenty-one percent of

participants eat a meal outside of the home at least 4-5 times per week. Another 24% of

participants eat meals outside the home 2-4 times per week. This is slightly lower than studies

that analyzed the CCHS 2004 data, which reported that 29% of adults in Ontario had eaten at a

fast food outlet on the day before their interview (Garriguet, 2004).

The majority of participants (78%) reported that they actively read the sodium content on

food labels and tried to purchase products that were low in sodium, contained no added salt or

were reduced in sodium. However, Wong et al (2013) demonstrated that Canadian consumers do

44

not seem to differentiate between different types of sodium claims. This is of concern as the

sodium content can vary widely depending on the type of claim that is displayed on the product.

To our knowledge there is no other data that describes the most commonly consumed

types of MPF products in the CKD population. Studies that have looked at dietary intake in the

CKD population have ranked food consumption according to specific nutrient intakes (Khoueiry

G et al. 2011; Fassett RG et al. 2007). Kalantar-Zadeh et al (2011) used a 3-day food record to

rank sources of energy intake among 154 hemodialysis patients in South Bay, Los Angeles, CA.

The most frequently consumed items (n=55) represented 83% of patients’ energy intake. The

study concluded that the top 5 sources of MPF according to percent of energy intake were eggs

or breakfast sandwiches with eggs; beef (fat off); chicken, not fried (no skin); mixed dish with

beef or pork; and hamburgers. The results are difficult to compare to ours as they ranked MPF

intake according to percent of energy intake and include additional information regarding animal

protein sources we did not inquire about, such as eggs and mixed dishes with beef or chicken. In

addition, the difference in the results between the Kalantar-Zadeh study and ours is possibly due

to the difference in populations of the two geographic areas. South Bay consists mainly of

individuals of Hispanic and African American ethnicity, whereas Toronto has a more ethnically

diverse population.

Our study has several limitations. First, we chose a convenience sample at a single centre

in Toronto, Ontario, which limits the generalizability of the results to the entire dialysis CKD

population. In addition, as this was a convenience sample, the possibility of selection bias cannot

be excluded. While we showed that characteristics, such as age and BMI, were similar to the

SMH dialysis population (see Table 4.5 & 4.6), we were not able to compare aspects such as

education level and household income, which may influence food purchasing and consumption

behaviours. Patients who do not cook at home were excluded from the study, and therefore the

results cannot be extrapolated to patients who obtain food elsewhere. Future studies could

address patients who eat food outside of the home (i.e. patients living in a nursing home or who

rely on fast food), as these are often convenience products which are likely to contain additives.

Lastly, although a wide variety of MPF foods were captured using a validated tool, general

limitations of food frequency questionnaires are that they lack the accuracy to assess the

adequacy of dietary intakes, they rely on the patient’s memory which can affect accuracy of the

results and they may not have adequate coverage to include all MPF food items consumed

45

(Brown, 2006; Bross et al, 2010). For instance, eggs were not included and have been shown to

be a significant source of animal protein intake (Pasiakos et al, 2015; Kalantar-Zadeh et al,

2011).

4.5.1 Conclusions

In conclusion, the most commonly consumed MPF by patients with CKD were chicken,

ground beef, steak, white fish, beef burgers, shrimp, deli ham and bacon. Participants generally

chose a fresh version of MPF products in accordance with a low sodium diet. However, they also

consumed certain types of high-sodium processed MPF products frequently, such as bacon and

deli ham. We conclude that participants often look at the nutrition facts table for the amount of

sodium and potassium. However, less than half of participants look for the word ‘phosphorus’ or

‘potassium’ on the ingredient list, which determines if the product contains additives.

This study provided information on amounts of MPF products consumed, as well as

purchasing and cooking behaviours. The results enabled us to select the most relevant MPF

foods for Canadian patients with ESRD, to be chemically analyzed in the next phase of the study.

46

5.0 Phosphorus and potassium content of commonly consumed meat, poultry

and fish products among patients with CKD

5.1 Introduction

Cardiovascular disease is a leading cause of mortality among patients with chronic

kidney disease (CKD) (USRDS, 2003). Hyperphosphatemia is associated with cardiovascular

mortality (Block et al, 1998; Kestenbaum et al, 2005; Palmer et al, 2011), whereas hyperkalemia

can lead to fatal arrhythmias or sudden cardiac death (Sanghavi et al, 2013). Low potassium and

low phosphorus diets are often prescribed to patients with CKD and form an integral part of their

nutritional therapy to manage and prevent hyperkalemia and hyperphosphatemia (Kopple &

Massry, 2004).

Adherence to low phosphorus and potassium diets is becoming increasingly difficult due

to the addition of phosphorus and potassium additives to foods. Phosphorus additives are often

added to meat, poultry and fish (MPF) products to extend shelf life, improve texture, and

preserve moisture (Lampila, 2013). Sodium phosphates can also be injected into solid cuts of

meat and poultry, in which case it may be labelled as ‘enhanced’ (U.S.) or ‘seasoned’ (Canada).

Several studies conducted in Europe and the United States have demonstrated that phosphorus

additives significantly contribute to the phosphorus content of food (Léon JB et al, 2013; Cupisti

A et al, 2012; Benini O et al, 2011; Sherman & Mehta, 2009b; Sullivan et al, 2007). Recently,

Carrigan et al. (2014) compared chemically analyzed foods from a low additive and an additive-

enhanced 4-day menu. The study demonstrated that a processed diet rich in additives increased

phosphorus content by 60%. To our knowledge, there is no published analytical Canadian data of

foods with phosphorus additives. In addition, studies that have looked at the contribution of

potassium additives to the potassium content of foods are limited (Sherman & Mehta, 2009b).

The problem of additives is compounded by the fact that phosphorus and potassium

contents are not listed on the Nutrition Facts table of food packages, unless there is a specific

nutrient-related claim (CFIA, 2015b; FDA 2013). Therefore, this creates uncertainty as to which

foods are appropriate to consume on a renal diet. In addition, it poses a challenge for renal

dietitians who are often advising patients on dialysis to consume animal sources of protein, many

of which may be hidden sources of phosphorus and potassium. The aim of this study was to gain

knowledge of the actual content of phosphorus and potassium in commonly consumed meat,

47

poultry and fish products, among the CKD population. Specific objectives were to determine

whether and to what extent the chemically analyzed phosphorus, potassium, sodium and protein

content differs among commonly consumed MPF products with and without additives listed on

their ingredient list and among poultry products with and without the term ‘seasoned’ on the

product label.

5.2 Materials and Methods

MPF products were chosen for chemical analysis based on the results of a food frequency

questionnaire (FFQ) administered to hemodialysis and peritoneal dialysis patients (n=67) during

July-September 2013 at St. Michael’s Hospital (Toronto, Ontario). Twenty-three questions

related to MPF consumption were extracted from the Canadian Diet History Questionnaire II

(DHQ II), from the National Institute of Health, adapted for Canada (Csizmadi et al, 2007). The

FFQ items asked about the frequency, amount and types of MPF consumption. In addition, data

was collected surrounding the purchasing and preparation behaviours, self-reported adherence to

renal diet restrictions, and clinical and demographic data.

Products from each type of commonly consumed MPF categories namely: unbreaded

chicken, ground beef, steak, white fish, beef burgers, deli meats, bacon and shrimp, were

purchased from the top 3 grocery stores in Canada. A concerted effort was made to purchase

store brands and national brands of each type of MPF product. If there were multiple brands,

products that occupied the most shelf space were chosen. In order to further examine the

contribution of additives, comparable reference products were also chosen for each type of MPF

product. A reference product was defined as a fresh MPF item that contained no additional

ingredients or additives. These products were purchased from local butchers or from companies

that could confirm no additives had been added to the product.

A minimum of 150 grams of MPF product was pre-weighed. Foods were cooked

according to package directions. If package directions were not available, foods were cooked

until they reached a safe internal cooking temperature (Government of Canada, 2015). Once

cooked, foods were stored into a re-sealable Ziploc® plastic bag, and kept refrigerated at 5° C

until analysis. All food packaging was retained for labelling information. A product was

considered ‘seasoned’ if the word seasoned was used anywhere on the food package. A product

was considered to contain a phosphorus or potassium additive if such an additive was listed on

48

the ingredient list. Foods sold at a deli, meat or seafood counter in Canada are not required to

have ingredients listed on the consumer package label. Original package information with an

ingredient list was obtained from the deli counter personnel to determine if deli ham contained a

phosphorus or potassium additive. Package information was not available for sole and tilapia

products sold at a seafood counter and therefore the addition of P and K additives for these

products was unknown.

The analyses for the protein, phosphorus, potassium and sodium content of food were

performed by Maxxam Analytics (Mississauga, Ontario). Samples were homogenized, and a

portion was used for nutrient analysis. Protein was analyzed according to the Association of

Analytical Communities (AOAC) official method 992.15 by combustion using TruMacTM

N

(LECO Corporation, St Joseph, MI). The total nitrogen was multiplied by the factor 6.25 to

calculate the protein content. Samples were run in batches and the instrument was corrected for

daily calibration drift. A blank, reference material, EDTA (ethylenediaminetetraacetic acid)

check, and duplicate of a random sample were run for each batch. A CCB (continuous

calibration blank) and CCV (continuous calibration verification) check were also run between

batches.

Phosphorus, potassium and sodium content were determined according to the AOAC

official method 984.27. The samples were digested in a mixture of nitric and hydrochloric acid,

and then analyzed by ICP-OES (inductively coupled plasma - optical emission spectrometry)

using a Thermo Scientific iCAP 6500 ICP instrument (Thermo Fisher Scientific Inc., Waltham,

MA). Samples were run in batches and a daily calibration, blank, matrix spike, duplicate of a

random sample and reference material were run for each batch. A CCB and CCV were also run

between batches. In addition, Maxxam Analytics participates in proficiency testing that

compares inter-laboratory results.

The potassium, phosphorus and sodium contents of each food item are expressed as mg

per 100g of product, while protein is expressed in g per 100g of product. Additionally, the ratio

of milligrams of phosphorus per gram of protein content is reported as the phosphorus to protein

ratio, because of its advantage of being independent from the weight of the food item. Food

categories for which MPF products did not contain an additive were excluded from the analyses

which compared additive, non-additive and reference groups. Comparisons between additive,

49

non-additive and reference groups were determined using Kruskal-Wallis test. If a significant

difference was observed, then Mann-Whitney tests were used for analysis between groups. A

similar approach was used for foods that were labelled seasoned, those not labelled seasoned and

reference foods. Results were considered statistically significant if p < 0.05. All analyses were

done using SPSS version 17.0 (Chicago, IL). The potassium, phosphorus, sodium and protein

content of MPF were compared to the Canadian Nutrient file values and results are reported in

Appendix I.

5.3 Results

Commonly consumed MPF (n=76) in twelve food categories, and comparable reference

foods (n=15) were purchased and chemically analyzed (Table 5.1). Phosphorus additives were

present on the ingredient list in 37% of MPF (Table 5.2), and were highly prevalent in bacon,

deli ham and shrimp products (100%, 73% and 57%, respectively) (Figure 5.1). All phosphorus

additives listed on the ingredient list were a type of sodium phosphate. Potassium additives were

found on the ingredient list in 9% of MPF and found in frozen chicken breast, unbreaded chicken

strips and deli ham products (Table 5.2). The word “seasoned” was found on the package label of

25% of MPF foods, with the majority of seasoned MPF being chicken products (Table 5.2).

Three tilapia and 3 sole products were purchased from the seafood counter where no labelling or

ingredient information was available (Figure 5.1).

Within MPF categories that contained a phosphorus additive (bacon, deli ham, shrimp,

sole, unbreaded chicken breasts, frozen chicken breasts and beef burgers), there was a significant

difference in the sodium, phosphorus and phosphorus to protein ratio among groups (Table 5.3, p

<0.001). No difference was seen in the potassium and protein content between groups. Further

analysis showed that foods listing a phosphorus additive on the ingredient list contained

significantly more phosphorus than foods that did not list a phosphorus additive (Table 5.3, p

<0.05). In addition, foods listing a phosphorus additive had a significantly greater phosphorus to

protein ratio and more sodium than its counterparts without a phosphorus additive and reference

foods (Table 5.3, p <0.05).

In order to gain insight into the extent of the contribution of phosphorus additives to

phosphorus content, we examined foods within MPF categories. Wide variability in phosphorus

content was noted for those foods where phosphorus additives were listed on the ingredient list

50

(Table 5.4). However, the phosphorus to protein ratio appeared to be consistently higher in MPF

foods listing a phosphorus additive compared to foods not listing a phosphorus additive and

reference foods (Table 5.4).

As chicken products contained the largest number of products using the word “seasoned”

on its packaging, only chicken products were included in the analysis of foods labelled seasoned

versus those not labelled seasoned. We found a significant difference in the sodium content

between foods labelled seasoned, foods not labelled seasoned and reference chicken products

(Table 5.5, p = 0.03). Additional analysis indicated that foods labelled seasoned had significantly

more sodium than reference products only (Table 5. 5, p < 0.05). There were no differences in

phosphorus, protein, phosphorus to protein ratio and potassium content among groups.

Among the food groups containing a potassium additive, namely frozen chicken breast,

unbreaded chicken slices and deli ham, there were significant differences in the sodium and

potassium content among foods listing a potassium additive, foods that did not list a potassium

additive and reference foods (Table 5.6, p = <0.05). Between group analyses revealed that foods

listing a potassium additive on the ingredient list had significantly more potassium than foods

without potassium additives and reference foods (Table 5.6, p < 0.05). Foods with and without a

potassium additive listed on the ingredient list had significantly more sodium than reference food

items (Table 5.6, p <0.05). There was a tendency for lower protein content of foods with

potassium additives, however differences were not significantly different. All potassium

additives included in foods were in the form of potassium lactate.

51

Table 5.1 Meat, poultry and fish food categories and comparable reference foods

Food Category n Reference Food n

Chicken Breast, Fresh 5

Chicken Breast 3 Chicken Breast, Frozen 8

Chicken Strips, Packaged 6

Chicken, Rotisserie 5

Ground Beef, Fresh 3 Ground Beef 3

Beef Burgers, Frozen 7

Steak, Fresh 3 Steak 3

Tilapia, Fresh/Frozen† 6 No reference available

Sole, Fresh/Frozen† 7 No reference available

Shrimp, Frozen 7 Shrimp 1

Deli Ham, Packaged 11 Pork Leg 2

Bacon, Packaged 8 Pork Belly 3

A reference product was defined as a fresh MPF item that contained no additional ingredients or

additives. Reference products (n=15) were purchased from local butchers or from companies that

could confirm no additives had been added to the product.

52

Table 5.2 Characteristics of meat, poultry and fish (MPF) products commonly consumed

by patients with chronic kidney disease (n=76)

MPF Category n

Contains

Phosphorus

Additives

Contains

Potassium

Additives

Labelled

Seasoned

Seafood /

Meat/Deli

Counter

n (%)

Chicken

Chicken Breast,

Fresh 5 0 (0) 0 (0) 0 (0) 0 (0)

Chicken Breast,

Frozen 8 2 (25) 1 (13) 8 (100) 0 (0)

Chicken,

Unbreaded

Strips, Packaged

6 2 (33) 2 (33) 3 (50) 0 (0)

Chicken,

Rotisserie 5 0 (0) 0 (0) 4 (80) 5 (100)

Beef

Ground Beef,

Fresh 3 0 (0) 0 (0) 0 (0) 0 (0)

Steak, Fresh 3 0 (0) 0 (0) 0 (0) 0 (0)

Beef Burgers,

Frozen 7 1 (14) 0 (0) 1 (14) 0 (0)

White Fish

Tilapia,

Fresh/Frozen† 6 0 (0) 0 (0) 0 (0) 3 (50)

Sole,

Fresh/Frozen† 7 3 (43) 0 (0) 0 (0) 3 (43)

Shrimp

Shrimp, Frozen 7 4 (57) 0 (0) 0 (0) 1 (14)

Processed Meat

Deli Ham 11 8 (73) 4 (36) 3 (27) 5 (46)

Bacon 8 8 (100) 0 (0) 0 (0) 0 (0)

*Alternate brand is national brand

† Tilapia (n=3) and Sole (n=3) purchased from the seafood counter do not include a list of

ingredients and it was unknown if these products contained phosphorus additives

53

Figure 5.1 Percent of MPF foods containing phosphorus additives on the ingredient list

according to MPF category (descending order)

Tilapia (n=3) and sole (n=3) purchased from the seafood counter do not include/require a list of

ingredients and it was unknown if these products contained phosphorus additives

54

Table 5.3 Comparison of analyzed nutrients content among MPF categories containing

phosphorus additives, without phosphorus additives and reference foods§

Reference

n=12

P additives

n=28

No P additives*

n= 26

Median (min,

max)

Median (min,

max)

Median (min,

max) p-value

†

Sodium

62 (41, 290)a 935 (200, 2800)

b 485 (130, 1100)

c < 0.001

Potassium

375 (66, 450) 295 (10, 1100) 305 (52, 920) 0.88

Phosphorus

210 (100, 260)a 270 (140, 500)

b 200 (130, 510*)

a < 0.001

Protein

23 (13, 29) 18 (12, 49) 20 (13, 30)

0.47

Phosphorus:Protein

8.7 (7.2, 9.3)a 12.5 (8.6, 19.9)

b 9.5 (7.4, 27.9)

c < 0.001

§Food groups containing phosphorus additives: Frozen chicken breast, unbreaded chicken strips,

beef burgers, sole, shrimp, deli ham and bacon

Abbreviation: P = Phosphorus

Phosphorus, Sodium, Potassium were analyzed and reported as mg/100g. Protein is analyzed and

reported as g/100mg. Phosphorus:Protein ratio is reported as mg P/g protein.

abc Medians significantly different by Mann-Whitney and p<0.05 if subscripts differ from each

other

†Kruskal-Wallis test

*includes foods from seafood counter where an ingredient list was not available

.

55

Table 5.4 Analyzed nutrient content of MPF categories with and without phosphorus

additives listed on the ingredient list and reference foods

Food Group Data Source n P Pro P:Pro Na K

Bacon†† P Additives 8 301 (115) 31 (11) 9.7 (0.8) 1625 (658) 355 (133)

Reference 3 123 (32) 17 (4) 7.4 (0.2) 71 (9) 233 (68)

Deli Ham†

P Additives 8 264 (33) 16 (2) 17.1 (3.2) 999 (67) 543 (346)

No P Additives 3 217 (29) 18 (5) 13 (5.9) 977 (21) 573 (287)

Reference 2 195 (64) 23 (8) 8.5 (0.1) 51 (1) 345 (106)

Shrimp,

Fresh/Frozen

P Additives 4 198 (57) 14 (2) 14.5 (4.5) 420 (67) 31 (21)

No P Additives 3 200 (82) 17 (3) 12 (5) 630 (61) 94 (56)

Reference 1 130 16 7.9 290 66

Sole,

Fresh/Frozen

P Additives 3 267 (25) 17 (3) 15.8 (1.7) 310 (106) 168 (79)

No P Additives* 4 290 (150) 16 (1) 17.3 (7.5) 295 (135) 152 (75)

Chicken strips,

unbreaded

P Additives 2 290 (14) 23 (1) 12.5 (0.1) 430 (42) 715 (544)

No P Additives 4 195 (19) 23 (1) 8.7 (0.9) 488 (147) 470 (194)

Reference 3 247 (15) 27 (2) 9.0 (0.2) 54 (12) 427 (25)

Chicken

breast, Frozen

P Additives 2 335 (35) 26 (4) 13.3 (3.6) 445 (346) 445 (35)

No P Additives 6 212 (22) 26 (2) 8.2 (1) 420 (55) 435 (243)

Reference 3 247 (15) 27 (2) 9.0 (0.2) 54 (12) 427 (25)

Beef Burger,

Frozen

P Additives 1 210 17 12.1 340 300

No P Additives 6 178 (29) 18 (4) 9.9 (1.1) 485 (54) 295 (54)

Reference 3 223 (25) 24 (3) 9.3 (0.1) 68 (14) 400 (50)

Tilapia,

Fresh/Frozen No P Additives* 6 205 (14) 20 (2) 10 (0.5) 58 (37) 390 (51)

Chicken

Breast, Fresh

No P Additives 5 260 (23) 28 (1) 9.2 (0.5) 56 (11) 444 (43)

Reference 3 247 (15) 27 (2) 9.0 (0.2) 54 (12) 427 (25)

Chicken,

Rotisserie

No P Additives 5 200 (12) 27 (1) 7.5 (0.5) 306 (90) 360 (26)

Top Sirloin

Steak, Fresh

No P Additives 3 270 (12) 31 (3) 8.7 (0.5) 66 (9) 460 (25)

Reference 3 263 (6) 30 (2) 8.7 (0.5) 63 (8) 460 (26)

Lean Ground

Beef, Fresh

No P Additives 3 203 (6) 23 (1) 8.9 (0.6) 71 (2) 367 (21)

Reference 3 223 (25) 24 (3) 9.3 (0.1) 68 (14) 400 (50)

Notes: No reference product available for Tilapia and Sole

Values for analyzed and reference foods are expressed as Mean (Standard Deviation)

P, Na, K were analyzed and reported as mg/100g. Pro is analyzed and reported as g/100mg. P:Pro

ratio is reported as mg P/g protein.

Abbreviations: Na = Sodium, K = Potassium, P = Phosphorus, Pro = Protein; P:Pro Ratio = Phosphorus to

protein ratio

†Reference product for deli ham is unprocessed pork leg

††Reference product for bacon is unprocessed pork belly

*Tilapia (n=3) and sole (n=3) purchased from the seafood counter do not include a list of ingredients and

it was unknown if these products contained phosphorus additives

56

Table 5.5 Comparison of analyzed nutrient content among chicken products labelled

seasoned, products not labelled seasoned and reference products

Reference

n=3

Labelled

Seasoned*

n=15

Not Labelled

Seasoned

n=9

Median (min,

max)

Median (min,

max)

Median (min,

max)

p-value†

Sodium 58 (41, 63)a

400 (200, 690)b

75 (49, 610)ab

0.03

Potassium 430 (400, 450) 370 (300, 1100) 420 (310, 490) 0.65

Phosphorus 250 (230, 260) 210 (190, 360) 240 (180, 290) 0.64

Protein 28 (26, 28) 25 (22, 30) 27 (22, 29) 0.41

Phosphorus:Protein 8.9 (8.8, 9.2) 8.0 (7.3, 15.8) 8.9 (6.9, 9.8) 0.64

*A product was considered ‘seasoned’ if the word seasoned was used anywhere on the food package abc

Medians significantly different by Mann-Whitney and p<0.05 if subscripts differ from each other

†Kruskal-Wallis test

Phosphorus, Sodium, Potassium, were analyzed and reported as mg/100g. Protein is analyzed and

reported as g/100mg. Phosphorus : Protein ratio is reported as mg P/g protein.

Table 5.6 Comparison of analyzed nutrient content among MPF foods containing

potassium additives, not containing potassium additives and reference foods§

Reference

n=5

K additives

n=7

No K additives

n= 18

Median (min,

max)

Median (min,

max)

Median (min,

max) p-value

†

Sodium 52 (41, 63)a

930 (280, 1100)b

590 (200, 1100)b

0.002

Potassium 420 (270, 450)a

900 (750, 1100)b

325 (260, 470)a

<0.001

Phosphorus 240 (150, 260) 270 (190, 300) 215 (190, 360) 0.32

Protein 28 (18, 29) 17 (13, 25) 23 (13, 30) 0.06

Phosphorus:Protein 8.8 (8.4, 9.2) 17.6 (7.7, 19.8) 9.7 (7.4, 19.9) 0.09

abc Medians significantly different by Mann-Whitney and p<0.05 if subscripts differ from each other

†Kruskal-Wallis test §Food groups containing potassium additives: Frozen chicken breast, unbreaded chicken slices, and deli

ham

Phosphorus, Sodium, Potassium, were analyzed and reported as mg/100g. Protein is analyzed and

reported as g/100mg. Phosphorus : Protein ratio is reported as mg P/g protein.

57

5.4 Discussion

Our study demonstrated that phosphorus and potassium additives significantly contribute

to the phosphorus and potassium content of MPF in Canada. Generally, foods that were frozen,

packaged or processed, such as frozen chicken breasts, unbreaded chicken strips and deli ham

were more likely to contain additives compared to fresh MPF. Products labelled as “seasoned”

surprisingly did not contain significantly more phosphorus than those not labelled as seasoned.

MPF foods with a phosphorus additive listed on the ingredient list contain a higher

amount of phosphorus and greater phosphorus to protein ratio than foods that do not list a

phosphorus additive. In MPF types containing products with and without additives (excludes

sole products), the higher phosphorus content of foods with phosphorus additives ranged from -

1% to 58%, with a mean increase of 29%. Our results are in line with existing literature from the

U.S and Europe, which have reported a 30-60% increase in phosphorus in additive-containing

foods (Léon JB et al, 2013; Cupisti et al, 2012; Benini et al, 2011; Sherman et al, 2009ab;

Sullivan et al, 2007). Food regulations in the U.S and Canada are similar, as they both allow

phosphorus additives to be added to meat and poultry products in amounts up to 0.5% of the

product formula (CFIA 2013; FSIS 2015). However, there is no maximum limit for the use

phosphorus additives in fish and seafood products in the United States, while the maximum use

in Canada is 0.5% (CFIA 2013, FDA 2014b). As all phosphorus additives were in the form of

sodium phosphate, there was significantly more sodium in MPF foods containing a phosphorus

additive. This study supports educating patients to avoid foods containing a phosphorus additive

on the ingredient list, especially given that it is a highly bioavailable form of phosphorus.

Furthermore, such intervention was previously shown to result in statistically significant

decreases in serum phosphorus concentrations (Sullivan et al, 2009).

While almost all food products contained an ingredient list, there were six fish products

that were purchased from a seafood counter where a list of ingredients was not available.

Therefore, we were unable to ascertain if these products contained phosphorus additives. As we

recognized that patients may assume these fresh seafood products do not contain additives, we

included the products in the analysis as “no phosphorus additive” foods. However, one sole

product had the highest phosphorus content and phosphorus to protein ratio of all foods

analyzed, (510 mg P/100g and 27.9 mg P/g Pro, respectively) and is therefore highly likely to

58

contain phosphorus additives. It has been revealed that sodium compounds may come into

contact with fish and seafood products during the commercial processing before they are sold in

retail stores (Ahuja et al, 2015). Hence, it would be prudent for patients to be aware and

informed of the potential of additives from fresh fish at a seafood counter.

Renal dietitians educate patients with CKD to avoid seasoned products, as these foods

may include phosphorus additives (ORN, 2013; Sherman & Mehta, 2009b). In our study, no

differences in the phosphorus content were noted in chicken products labelled as ‘seasoned’

compared to those that were not labelled as seasoned. According to the Canadian Food

Inspection Agency (CFIA), the term ‘seasoned’ reflects a solid cut of meat that contains one of:

phosphate salts; phosphate salts and water; or spices and water. Therefore, the term ‘seasoned’ is

not synonymous with phosphorus additives. Only 4 of 15 products labelled ‘seasoned’ contained

a phosphorus additive, so it is possible that the other products contained spices and water which

did not add to the phosphorus content of the food. Injection of solutions into poultry is common

and is estimated to occur in 30% of chicken products in the U.S (Ahuja et al, 2015). Sherman &

Mehta (2009b) measured the phosphorus content of 36 uncooked meat and poultry products and

determined that enhanced products contained a higher phosphorus to protein ratio. Notably, the

authors indicated that 39% of enhanced products listed a phosphorus additive which is a higher

percentage compared to our results. ‘Seasoned’ products contained higher amounts of sodium

than reference MPF foods, and therefore, those patients requiring a dietary sodium restriction

should be educated to choose fresh MPF without additives and avoid ‘seasoned’ poultry.

However, in Canada, dietitians should re-consider the impact of educating patients to avoid

‘seasoned’ chicken products as part of a low phosphorus diet, given our findings. Our study

shows that it would be more effective to educate patients requiring a phosphorus restricted diet to

avoid foods with a phosphorus additive listed on the ingredient list.

The higher amount of potassium in MPF foods listing a potassium additive compared to

those without potassium additives was remarkable. While there was a wide range in the

potassium content of foods containing a potassium additive, two of the products analyzed

contained 1100 mg of potassium per 100g. This a concerning amount of potassium, especially

for patients with CKD requiring a potassium restriction, as this amount contributes to more than

half of their daily recommended intake of less than 2000 mg of potassium (Nelms et al, 2007). In

addition, patients with impaired urinary potassium excretion such as those with heart failure,

59

diabetes and those taking angiotensin converting enzyme inhibitors and angiotensin receptor

blocker medications are at increased risk of life-threatening hyperkalemia (IOM, 2005) and may

be unaware of the potential high potassium content of these foods. We have determined that

sodium reduced foods that listed a potassium additive on the ingredient list had on average, more

than double the amount of potassium compared with sodium reduced foods that did not list a

potassium additive (713 mg/100g versus 350 mg K/100g) (Sharma Parpia et al, 2014, Chapter 6).

We attribute the large increase in potassium content to the fact that potassium lactate, the type of

potassium additives found in analyzed products is allowed as an antimicrobial agent up to 4% in

meat and poultry products in Canada, and 4.8% in the U.S. (Health Canada, 2012b; FSIS, 2012).

This is considerably greater than the allowable amount of phosphorus additives (0.5%), therefore

potassium lactate may have a greater potential to contribute to the potassium content of meat and

poultry products.

While previous studies have examined the contribution of phosphorus and potassium

additives to the nutrient content of foods, this is the first study to chemically analyze foods for

this purpose in Canada. Strengths of our study include that a representative sample of foods were

chosen for analysis and were relevant to the food consumption and preparation habits of patients

with CKD. In addition, we included additive-free reference foods which acted as a control for

possible mislabelling of MPF products. However, this is a cross sectional study that is only

applicable to the study time period as food products are often reformulated. As new phosphorus

and potassium additives are continuously being approved for use in various types of food, it is

likely that the contribution of potassium and phosphorus from additives will increase over time.

While efforts were made to choose store and national brands, products were purchased from

Toronto, Ontario, where the food supply may be different than other geographical regions.

In conclusion, MPF foods with a phosphorus and/or potassium additive on the ingredient list

significantly contributes to the phosphorus and potassium content of the food. Patients with CKD

should be educated to avoid MPF foods containing a phosphorus additive, and particularly

potassium additives where there is a marked increase in potassium content from potassium

lactate. In Canada, we found the term ‘seasoned’ does not always imply the food item contains

phosphorus additives or higher phosphorus content, but does contain high amounts of sodium. In

addition, patients should be cautious when purchasing fish and seafood from a counter as these

foods do not contain an ingredient list and may contain additives. Generally, MPF foods that

60

were fresh were least likely to contain additives. Therefore, encouraging consumption of fresh

MPF products may lead to improved dietary compliance in patients with CKD.

61

6.0 Do Sodium Reduced Meat and Poultry Products Contain a Significant

Amount of Potassium and Phosphorus from Additives?

This manuscript has been submitted to the Clinical Journal of the American Society of

Nephrology for publication: Parpia AS, Goldstein MB, Arcand J, L’Abbé MR, Darling PB.

Sodium Reduced Meat and Poultry Products Contain a Significant Amount of Potassium from

Additives

This study was presented in part at the American Society of Nephrology Kidney week,

Philadelphia, PA, November 11-16, 2014. The abstract was published in the Journal of the

American Society of Nephrology. 2014; 25:685A

6.1 Introduction

The reduction of sodium in processed foods is a key component of population-wide

health strategies being implemented by various countries in an effort to reduce the sodium intake

of individuals (Mohan et al, 2009). Current American and Canadian recommendations are that

food manufacturers lower the sodium content of their food products (Henney et al, 2010; Health

Canada, 2010). As sodium chloride acts to preserve and enhance the taste and texture of meat

and poultry products (MPP), food manufacturers may use phosphorus and potassium additives to

replace the functional and flavor properties of sodium chloride (Verma & Banerjee, 2012).

Phosphorus additives are increasingly being added to MPP as they increase shelf-life,

retain moisture, maintain color and improve texture (Kalantar-Zadeh et al, 2010; Murphy-

Gutekunst & Uribarri, 2005). Studies have demonstrated that phosphorus additives significantly

contribute to the dietary phosphorus load which can contribute to hyperphosphatemia and its

respective complications in patients with chronic kidney disease (CKD) (Benini et al, 2011;

Carrigan et al, 2014; Leon et al, 2013; Sullivan et al, 2007; Sherman & Mehta, 2009ab; Bell et

al, 1977).

Potassium additives, such as, potassium chloride, confer a salty taste and are often used

for sodium replacement in sodium reduced foods (Dotsch et al, 2009). Potassium lactate and

potassium phosphate have the added benefits of improving shelf-life and moisture retention in

MPP (Verma & Banerjee, 2012; Desmond, 2006; Ruuseunen et al, 2002; Health Canada, 2014).

While evidence suggests that a diet high in potassium from fruits, vegetables and low-fat dairy is

62

associated with a significant blood pressure lowering effect (Sacks et al, 2001) and may be

advantageous to the general population (Salehi-Abargouei et al, 2013), an increased potassium

load from additives could potentially contribute to hyperkalemia and fatal arrhythmias in patients

with CKD. Life-threatening hyperkalemia due to use of potassium containing salt substitutes has

been reported to affect individuals with impaired renal excretion, as well as patients with heart

disease (Doorenbos & Vermeij, 2003; John et al, 2011). The risk of hyperkalemia is further

increased with the use of medications such as angiotensin-converting enzyme inhibitors,

angiotensin II receptor blockers and potassium-sparing diuretics, especially when taken

concomitantly with salt substitutes (Ray et al, 1999).

Patients with CKD are educated to restrict sodium intake, which includes choosing low

sodium alternatives (NKF, 2015). Due to the possible inclusion of phosphorus and potassium

additives as a sodium replacer, it is unclear if sodium reduced foods are suitable for inclusion in

a renal diet. Currently, the phosphorus and potassium content of packaged foods are not included

on the Nutrition Facts table. Thus it is difficult for patients and health care providers to assess the

contribution of additives to the intake of those nutrients in order to make appropriate food

choices. The primary objective of this study was to determine whether and to what extent the

reduction of sodium in MPP is associated with increased amounts of potassium and phosphorus

from food additives.

6.2 Materials and Methods

This was a cross-sectional study of MPP selected for chemical analysis. Stores from the

top three grocery store chains in Canada were scanned for all sodium reduced MPP in May 2014.

An inclusive sample of all sodium reduced products with a corresponding original non-sodium

reduced counterpart (n=38) were selected. We considered a product to be sodium reduced if the

package label had a nutrient content claim stating the percentage reduction in sodium (eg. “25%

less sodium than our original product”). The “original product” of the same brand, but without

the sodium reduction claim was selected as the original non-sodium reduced counterpart. In

addition, reference foods were used in order to act as a control and to gain insight into the

magnitude to which additives contribute to the phosphorus and potassium content of the food.

The two types of reference foods were: 1) non-packaged additive-free reference foods (Ref-0)

(n=5) and 2) packaged potassium and phosphorus additive-free reference foods (Ref-KP)

63

(n=8).The fresh, Ref-0 foods were purchased from local butchers and contained no additional

ingredients or additives. The Ref-KP foods were processed MPP that were labeled as being

“Made with natural ingredients. No preservatives added”. While these products did not have any

potassium or phosphorus additives on the ingredients list, they did contain other additives, such

as sodium.

A minimum of 200 grams of product was cooked according to package directions, stored

into a re-sealable Ziploc® plastic bag, and kept at 5° C until analysis. All original food packages

were retained for labeling information. Protein, phosphorus, potassium and sodium were

analyzed by Maxxam Analytics (Mississauga, Ontario). Samples were homogenized and a

portion was used for nutrient analysis.

Protein was analyzed according to the Association of Analytical Communities (AOAC)

official method 992.15 by combustion using TruMacTM

N (LECO Corporation, St Joseph, MI).

The total nitrogen was multiplied by the factor 6.25 to calculate the protein content. Samples

were run in batches and the instrument was corrected for daily calibration drift. A blank,

reference material, EDTA (ethylenediaminetetraacetic acid) check, and duplicate of a random

sample were run for each batch. A CCB (continuous calibration blank) and CCV (continuous

calibration verification) check were also run between batches.

Phosphorus, potassium and sodium content were determined according to the AOAC official

method 984.27. The samples were digested in a mixture of nitric and hydrochloric acid, and then

analyzed by ICP-OES (inductively coupled plasma - optical emission spectrometry) using a

Thermo Scientific iCAP 6500 ICP instrument (Thermo Fisher Scientific Inc., Waltham, MA).

Samples were run in batches and a daily calibration, blank, matrix spike, duplicate of a random

sample and reference material were run for each batch. A CCB and CCV were also run between

batches. In addition, Maxxam Analytics participates in proficiency testing that compares inter-

laboratory results.

The potassium, phosphorus and sodium contents of each food item were expressed as mg

per 100g of product, while protein was expressed in g per 100g of product. Additionally, the

ratio of mg of phosphorus per g of protein content is reported as the phosphorus to protein ratio,

with the advantage of its independence from the size of the food serving (K/DOQI, 2003).

Results are summarized as mean and standard deviation. Differences between the original and

64

sodium reduced MPP were determined using paired t-test. Comparisons between original,

sodium reduced and reference foods groups were determined using one-way anova. If a

significant difference was observed, then t-tests were used for analysis between groups. Results

were considered significant at p<0.05. All analyses were done using SPSS version 17.0

(Chicago, IL).

6.3 Results

Sodium reduced MPP (n=19) contained on average 44% more potassium (mg/100g)

compared with their original non-sodium reduced counterparts, with an average difference of

184 mg/100g (95% confidence interval (CI): 90-279; p< 0.001) (Table 6.1). There was 38% less

sodium in products that had been sodium reduced compared to original counterparts, with an

average difference of 486 mg/100g (95% CI: 334-638; p <0.001). The difference in the amounts

of phosphorus and protein was not statistically significant. The original non-sodium reduced

foods had a slightly higher (p=0.009) phosphorus to protein ratio.

Table 6.2 compares mean values of reference foods with sodium reduced and original

MPP. There was an overall significant (p<0.05) difference in the sodium, potassium, phosphorus

and phosphorus to protein ratio among groups. Between group analysis revealed that REF-0

products had significantly less (p<0.05) sodium, compared to the sodium reduced MPP, original

non-sodium reduced, and REF-KP products. The REF-KP products had similar amounts of

phosphorus and potassium as REF-0 products, however these products contained significantly

higher sodium (p<0.05). Both REF-0 and REF-KP products contained significantly less (p<0.05)

phosphorus and potassium compared to sodium reduced foods (Table 6.2).

Further detail on individual products, including the presence of additives and sodium

claims, is shown in Table 6.3. The potassium content of sodium reduced products ranged from

210-1500 mg. Potassium containing additives were found on the ingredient list in 63% of the

sodium reduced products and in only 25% of the non-sodium reduced products (p = 0.02). Mean

potassium content of sodium reduced products with a potassium additive listed on the ingredient

list was 713 mg/100g versus 320 mg K/100g in sodium reduced foods without listed potassium

additives (p=0.002). In contrast, phosphorus-containing additives, such as sodium phosphate,

were found on the ingredient list in 68% of sodium reduced products and 95% of original non-

65

sodium reduced products. There was a 21% increase in the use potassium phosphates in sodium

reduced products (Table 6.3 and Figure 6.1).

Table 6.1 Comparison of analyzed nutrient levels in paired sodium reduced and original (non-

sodium reduced) meat and poultry products

Na, K, and P are measured in mg/100g. Protein is measured in g/100mg. Phosphorus to protein

ratio is measured in mg P/g protein.

Abbreviation: Na = Sodium; K = Potassium; P = Phosphorus; SD = standard deviation; CI =

Confidence Interval

Value expressed at Mean (SD), unless noted otherwise.

Statistical analyses comparing matched pairs of original and Na-reduced meat and poultry

products were done using paired t-tests. p <0 .05 was considered statistically significant.

Nutrient Na -Reduced

(n=19)

Original

(n=19)

Mean Paired

Difference

(95% CI)

p-value Mean Percent

Change

Na 749 (299) 1236 (548) -486 (-638, -334) < 0.001 ↓ 38 (11)

K 568 (334) 383 (173) 184 (90, 279) 0.001 ↑ 44 (43)

P 253 (75) 265 (87) -13 (-34, -8) 0.20 ↓ 3 (16)

Protein 25 (9) 23 (9) 1 (0.8, 3) 0.26 ↑ 6 (18)

P:Protein

ratio

10.8 (2.6) 11.5 (3.0) -1.1 (-1.9, -0.3) 0.009 ↓ 8 (13)

66

Table 6.2 Comparison of sodium reduced, original (non-sodium reduced), and reference meat

and poultry products

Nutrient

Reference-0

(n=10)

Reference - KP

(n=8)

Original

(n=18)

Na-Reduced

(n=19) p-value

†

Na

60 (11)a

866 (215)bc

1235 (577)c

749 (299)b

< 0.001

K

342 (96)a

384 (64)a

383 (173)a

568 (334)b

0.03

P

193 (60)b

188 (33)ab

265 (87)c

254 (75)dc

0.02

Protein

24 (6)

22 (5) 24 (9) 24 (9) 0.94

P:Protein

Ratio

8.1 (0.7)c

8.5 (0.8)ac

11.5 (3.0)d

10.8 (2.7)bd

0.001

Na, K, and P are measured in mg/100g. Protein is measured in g/100mg. Phosphorus to protein

ratio is measured in mg P/g protein.

abcd Medians significantly different by independent t-test and p<0.05 if subscripts differ from

each other

†One-way anova test

Abbreviation: Na = Sodium; K = Potassium; P = Phosphorus; SD = standard deviation; CI =

Confidence Interval; Ref-0 = Additive-free reference food; Ref-KP = Potassium and phosphorus

additive-free reference food

Value expressed at Mean (SD), unless noted otherwise.

67

Table 6.3 Chemical analysis of sodium, potassium, phosphorus and protein content of paired original (non-sodium reduced) and

sodium-reduced meat and poultry products

# Original (Non-Sodium Reduced) Sodium-Reduced

Original Product Na K P Pro PO4

AdditivesListed

K Additives

Listed Sodium Reduced Product Na K P Pro

PO4 Additives

Listed

K Additives

Listed

Reduction in Na (%)

Change in K (%)

1 President's Choice

Extra Lean Stone Roasted Ham 950 320 270 18 Y N

45% less sodium than PC Traditional Black Forest Ham

560 520 270 22 Y Y 41 +63

2 President's Choice

Stone-Roasted Ham Rosemary & Black Pepper

950 320 270 18 Y N 45% less sodium than PC

Traditional Black Forest Ham 620 600 310 22 Y Y 35 +88

3 President's Choice

Oven Roasted Turkey Breast 770 450 260 19 Y Y

55% less sodium than PC Oven Roasted Turkey Breast

460 950 260 22 Y† Y† 40 +111

4 President's Choice Tomato and Basil

Oven Roasted Turkey Breast 770 450 260 19 Y Y

30% less sodium than PC oven roasted turkey breast

550 800 240 19 Y Y 29 +78

5 President's Choice

Oven Roasted Chicken Breast 760 420 240 19 Y Y

40% less sodium than PC oven roasted chicken breast

550 520 290 21 Y Y 28 +24

6 Schneider's Olde Fashioned Fully Cooked Smoked Ham

1000 910 270 17 Y Y 25% less sodium than our

regular Olde Fashioned Ham 600 1500 200 18 Y† Y† 40 +65

7 Maple Leaf

Flakes of Ham (canned) 940 280 230 17 Y N

33% less sodium that our regular flakes of ham

590 260 220 18 Y N 37 -7

8 Maple Leaf Top Dogs

1200 540 260 14 Y Y 25% less salt than our original 790 850 210 13 Y† Y† 34 +57

9 President's Choice

Breakfast Sandwich Pork Sausage

830 310 170 20 N N 30% less sodium that PC breakfast sandwich pork

sausage 610 410 220 26 N N 27 +32

10 President's Choice

Naturally Smoked Bacon 1500 350 300 32

Y

N 50% less salt than regular PC

bacon 1200 340 320 30 Y N 20 -3

11 No Name

Mild Sugar Cured Bacon 1500 240 170 18 Y N

50% less salt that no name bacon

770 210 150 19 Y N 49 -13

12 Maple Leaf

Bacon 1200 290 260 27 Y N

33% less salt than our regular bacon

490 270 250 27 Y N 59 -7

13 Schneider's

Naturally smoked bacon 800 230 280 26 Y N

40% less salt per 50g serving than our regular bacon

400 500 180 24 Y Y 50 +117

14 Irresistibles

Bacon 1100 220 150 17 Y N

40% less salt than selection bacon

840 370 170 28 N N 24 +68

68

15 Selection

Bacon 1100 220 150 17 Y N

50% less salt than regular selection bacon

840 210 140 16 Y Y 24 -5

16 President's Choice

Fully Cooked Bacon 2300 470 380 35 Y N

50% less salt than PC fully cooked bacon

1000 380 330 33 Y N 56 -19

17 Maple Leaf

Fully Cooked Bacon 1800 470 370 41 Y N

50% less salt than our regular fully cooked bacon

1100 740 390 48 Y Y 39 +57

18 Compliments

Naturally Cooked Fully Cooked Bacon

2800 570 500 49 Y N 50% less salt than our

compliments fully cooked bacon 1600 1000 410 43 Y Y 43 +75

19 Butterball

Bacon Style Turkey 1200 230 280 20 Y N

50% less salt than our original bacon style turkey

660 360 260 18 Y† Y† 45 +57

Abbreviation: Na = Sodium; K = Potassium; P = Phosphorus; Pro = Protein

Values for sodium, potassium, phosphorus are reported in mg/100g. Values for protein are reported in g/100g. †Includes a potassium phosphate additive (i.e.potassium phosphate, potassium pyrophosphate) in the ingredient list on product label

69

Figure 6.1 Presence and type of additives in original and sodium reduced meat and poultry

products (MPP)

Note: Phosphorus Additives and Potassium Additives groups exclude foods listing potassium

phosphate on the ingredient list

0

10

20

30

40

50

60

70

80

90

100

PhosphateAdditives

PotassiumAdditives

PotassiumPhosphate*

% o

f M

PP

conta

inin

g a

dditiv

es

Original (n=19)

Sodium-Reduced (n=19)

70

6.4 Discussion

We demonstrate significantly greater amounts of potassium in sodium reduced meat and

poultry foods. The higher potassium content is due to the increased prevalence of potassium

additives, such as potassium chloride, potassium lactate, and potassium phosphate, which

manufacturers are likely using as a sodium replacer. The wide variability in potassium content

was remarkable, for example one sodium reduced product contained 1500 mg of potassium in a

typical serving (100g or 3.5oz) of cooked meat product. This amount is 75% of the

recommended daily intake of potassium for an individual with moderate to severe kidney disease

(Nelms et al, 2007) and is equivalent to taking approximately two doses of the 20mEq potassium

chloride supplement, K-Dur® (K/DOQI, 2004). This is of concern as an oral potassium load such

as this can produce a significant increase in serum potassium (Allon et al, 1993; Fernandez et al,

1986) in patients with end-stage renal disease, and along with usual dietary potassium intake

from other food sources, may subsequently lead to hyperkalemia which is associated with

arrhythmias and sudden cardiac death (Sanghavi et al, 2013). In one study by Noori et al (2010),

higher dietary potassium intake was associated with increased mortality in patients on

hemodialysis. Furthermore, as meat and poultry is not commonly considered as a high potassium

food source, it would be very difficult for the patient with hyperkalemia and health care team to

identify the source of dietary potassium.

Patients are often educated to select lower sodium foods, and may perceive sodium

reduced foods as being advantageous without realizing the potential for higher potassium content

in these foods. Sodium reduced products with a potassium additive listed on the ingredients list

contained, on average, more than double the amount of potassium compared to products with no

potassium additives on the ingredients list. Currently, product label information on potassium

content is available for less than 10% of packaged food products in the United States (Curtis et

al, 2013). More recently, the Health Canada and U.S. Food and Drug Administration have both

proposed that potassium be included in future Nutrition Facts tables on all packaged products,

which would provide important information to help guide those who need to limit dietary

potassium.

Interestingly, there was no difference in the phosphorus content between the sodium

reduced and original formulations of food products. This is likely due in part to the fact that

71

phosphorus additives were more prevalent in original non-sodium reduced products (95%) than

sodium-reduced products (68%). In several products, manufacturers replaced sodium phosphate

with a potassium phosphate additive in order to reduce the sodium in the product, resulting in a

21% increase in the use of potassium phosphates in sodium reduced products. This is not entirely

surprising, as five of the 11 phosphate salts approved for use in the United States are potassium

salts (Sherman & Mehta, 2009b). We therefore attribute the increase in potassium and

unchanged phosphorus in these sodium reduced products to the substitution of phosphorus

additives by potassium additives.

Although the REF-KP products were lower in potassium and phosphorus, they were as

high in sodium as the original non-sodium reduced product and thus are not appropriate for

patients needing to follow a renal diet. Choosing the Ref-0, non-packaged additive-free fresh

version of the meat and poultry in its unprocessed or unaltered state would be considered the best

option with regards to potassium, phosphorus, phosphorus to protein ratio and sodium content.

However, issues such as lack of convenience, lack of cooking skills and the complexity of the

renal diet remain large barriers to diet adherence in this population (Wright & Cavanaugh, 2010;

Venegoor, 2009; Moubarac et al, 2014).

There are few published data on the potassium content of foods. Sherman & Mehta

(2009b) measured the potassium content of 36 uncooked MPP and found that enhanced products,

injected with a sodium and additive-containing solution, contained 8.7% more potassium than

regular (non-enhanced) products. Our results are in line with those published by Sherman &

Mehta (2009b) as they also noted that there was marked variability in potassium content, with

the potassium content of enhanced MPP ranging from 170 to 930 mg/100g.

While no other study to our knowledge has chemically analyzed the potassium content in

sodium reduced MPP, Jaffery & Hood (2006) compared the phosphorus content in low sodium

and regular sodium foods obtained from the USDA food composition tables. He reported no

difference in phosphorus content in the majority (68%) of products measured.

It should be noted that our study is a cross-sectional analysis of MPP obtained from one

geographical area. Although many of the foods analyzed were national brands, the formulation

of these products can change over time, thus altering the nutritional content.

72

In conclusion, potassium additives are frequently added to sodium reduced meat and

poultry products in amounts that significantly contribute to the potassium load for patients with

chronic kidney disease and others with impaired renal excretion of potassium. Patients requiring

a potassium restriction should be educated to avoid sodium reduced meat and poultry products.

Our results support the inclusion of potassium content as a mandatory component on food

labeling to potentially decrease the risk of life-threatening hyperkalemia from sodium reduced

foods in vulnerable populations.

73

7.0 Overall Discussion & Conclusions

We have identified that the most commonly consumed meat, poultry and fish products

among patients on dialysis in Toronto, Canada were chicken, ground beef, steak, white fish, beef

burgers, shrimp, deli ham, and bacon. Participants generally chose a fresh version of MPF

products in accordance with a low sodium diet. The majority of patients (78%) also reported

checking for sodium on the Nutrition Facts table. However, they consumed certain types of high-

sodium processed MPF products frequently, such as bacon and deli ham. Likewise, a recent

study among CKD patients in England demonstrated that 87% of patients reported consumption

of tinned or processed meats at least once per week (Nerbass et al, 2014).

This was the first study to our knowledge to specifically examine the types of MPF foods

most commonly consumed among the dialysis population. As these patients are educated to

increase consumption of high biological value protein, it is valuable for health care providers to

gain an understanding of their intake patterns. Previous studies that have examined dietary intake

in the CKD population differ from our study findings as they have ranked food sources more

generally according to percent of energy intake or to a specific nutrient intake such as fatty acid.

In addition, their study population resided in a different geographical region (Khoueiry et al,

2011; Fasset et al, 2007; Kalantar-Zadeh et al, 2002). While it has been shown that animal

protein contributes to 46% of total protein intake (Pasiakos et al, 2015), it is important to note

that our FFQ did not assess intake of plant protein, dairy or egg intake. The results of Study 1

add to our current understanding of the dietary intake and food consumption behaviours of

patients with end-stage renal disease (ESRD) in Canada. Furthermore, the results enabled us to

select relevant MPF foods that our patients with ESRD commonly consume, for analysis in

Study 2.

There is no data to our knowledge describing the contribution of phosphorus and

potassium additives to the nutrient content of foods in Canada. This creates a challenge for both

patients with CKD and their clinicians to determine which foods are appropriate to consume

while on renal diet. In Study 2, we determined that MPF foods containing a phosphorus and/or

potassium additive on the ingredient list significantly contributes to the phosphorus and

potassium content of MPF foods. Potassium and phosphorus additives were generally found in

packaged, frozen or processed MPF foods, as opposed to fresh MPF foods. According to the

74

results of our questionnaire, less than half of participants looked for the word ‘phosphorus’ or

‘potassium’ on the ingredient list, which determines if the product contains additives. This is an

important finding as it indicates an area for improvement in patient education.

Phosphorus additives can increase the phosphorus content of foods by up to 59%. These

results were not entirely surprising as many studies that have taken place in the United States

(U.S.) and Europe demonstrated that the phosphorus content of foods with additives similarly

ranged from approximately 30 to 60% higher compared to foods that did not contain a

phosphorus additive (Léon et al, 2013; Cupisti et al, 2012; Benini et al, 2011; Sherman et al,

2009ab; Sullivan et al, 2007). In addition, regulations regarding the use of phosphorus additives

in meat and poultry foods in the U.S. are comparable to regulations in Canada as both countries

allow phosphorus additives in amounts up to 0.5% of the product formula by weight in meat and

poultry products (CFIA 2013, FSIS 2015). Phosphorus additives are considered to contribute to

the dietary phosphorus load as they are entirely bioavailable, unlike phosphorus naturally found

in foods which is only 40-60% absorbed in the gastrointestinal tract (Calvo et al, 2014).

Education regarding the avoidance of foods with phosphorus additives has been previously

shown to be an effective intervention for reducing serum phosphorus levels in the short term

(Sullivan et al, 2009). This in turn, may help moderate hyperphosphatemia and its complications,

however further studies are needed to demonstrate the effectiveness of dietary phosphorus

restriction on morbidity and mortality outcomes.

Meat and poultry products listing potassium lactate on the ingredient list contained up to

1100 mg of potassium in a 100g serving, which is more than half of the daily recommendation

for a patient with CKD requiring a potassium restriction (Sanghavi et al, 2013). These results

were in line with a previous study by Sherman & Mehta (2009b) where the authors noted the top

five enhanced products with the most potassium contained 692-930 mg potassium per 100

grams, which is considerably greater than the average potassium content of meat and poultry

products of the same weight (~300-375 mg K/100g). Potassium lactate is allowed up to 4% of

meat and poultry products in Canada (Health Canada, 2012b), which is equivalent to 1200 mg of

potassium in a 100g product and substantially greater than the maximum allowable amount of

phosphorus additives (0.5%) (CFIA, 2013). Therefore, potassium lactates may have the potential

to significantly contribute to the potassium content of meat and poultry products in Canada.

75

A previous study showed that MPF products injected with solutions by manufacturers

(labelled as ‘enhanced’ or ‘seasoned’) had significantly higher phosphorus to protein ratios than

foods that were not injected with solutions (Sherman & Mehta, 2009b). Therefore, it was a

surprising finding that poultry products labelled as ‘seasoned’ did not result in higher amounts of

phosphorus than products that were not labelled as ‘seasoned’. We attribute these results to the

fact that in Canadian regulations, the term ‘seasoned’ is not synonymous with the use

phosphorus additives. Therefore, we concluded that it is more effective for patients requiring a

dietary phosphorus restriction to look at the list of ingredients to determine if a product contains

an additive. If a product does not contain a list of ingredients, for example, fish from a seafood

counter, it is possible the product contains additives. In keeping with this finding, Ahuja et al

(2015) noted that sodium compounds may come in contact with fish and seafood products during

commercial processing.

We revealed in our study using a food questionnaire that approximately half of patients

reported choosing sodium reduced products most of the time. Importantly, study 3 determined

that sodium reduced meat and poultry products contain significantly more (44%) potassium that

their non-sodium reduced counterparts due to the use of potassium additives as a sodium

replacer, and are a significant source of potassium. Sodium reduced meat and poultry products

contain on average 38% less sodium and similar amounts of phosphorus and protein compared to

its original non sodium reduced counterpart. This was the first study to chemically analyze and

compare original and sodium reduced food product formulations.

As population-wide health strategies to reduce sodium levels in processed foods are being

implemented in various countries, such as Canada, United Kingdom and the U.S (Webster et al,

2014), sodium reduced food products will be increasingly available to consumers. In addition,

food additives containing phosphorus and potassium are continuously being approved for sodium

reduction and their use is likely underestimated. Manufacturers may be inclined to use potassium

additives due to its efficacy in lowering sodium and increasing potassium, which are both

associated with beneficial health outcomes. While the effects of potassium from fruits and

vegetables are known to be beneficial in the healthy population, the consequences of increased

potassium from potassium additives is not known and might be lead to unintentional negative

health effects in those with compromised kidney function.

76

The general population is likely unaware of the potential increase in potassium-based

additives in sodium reduced meat and poultry products. Furthermore, severe heart failure, kidney

disease and medications such as potassium-sparing diuretics, angiotensin converting enzyme

inhibitors and angiotensin receptor blockers can lead to impaired urinary potassium excretion.

With the increased prevalence of kidney disease, diabetes, heart failure and the use of multiple

anti-hypertensive agents, the risk of life-threatening hyperkalemia is likely to rise. Our results

support the inclusion of potassium content as a mandatory component on food labeling to

potentially decrease the risk of life-threatening hyperkalemia from potassium additives in

vulnerable populations.

7.1 Study Implications for Practice and Future Studies

Our findings directly impact nutrition education strategies and interventions for patients with

CKD in Canada. Patients should be educated to choose fresh, unpackaged versions of MPF

without additives most often as these foods have the least amount of sodium, phosphorus and

potassium. The exception to this guidance may be fresh seafood from a seafood counter, for

which an ingredient list is often not available and additives may be present. Therefore, the

availability of product information should be encouraged for products from the seafood counter.

Dietitians should be made aware that the term ‘seasoned’ is not synonymous with

phosphorus additives in poultry products. Seasoned products contain high amounts of sodium

and are not appropriate for those following a low sodium diet, such as those with CKD. For the

purpose of phosphorus restriction, it would be most effective to educate patients to identify and

avoid MPF products with phosphorus additives on the ingredient list. Since less than half of

patients surveyed reported looking for additives on the ingredient list, it would be beneficial to

increase efforts in educating patients to read the ingredient list to search for phosphorus

additives, and particularly potassium additives where there is a marked increase in potassium

content from potassium lactate.

Lastly, patients should be educated regarding the potential for increased potassium content in

sodium reduced meat and poultry products. Patients should be cautious when choosing sodium

77

reduced foods and look for potassium additives on the ingredient list, as well as the potassium

content on the nutrition facts table, if available.

Since there is wide variability in the phosphorus and potassium content of MPF foods

containing additives, it would be ideal for consumers to be able to access the nutrient content

information of these MPF products. Preferably, if food products containing additives had

phosphorus and potassium content present on the nutrition facts table, this may facilitate greater

adherence with dietary restrictions and allow for more food choices within the parameters of the

renal diet. Our findings can be used to advocate to policy makers for the requirement of

potassium and phosphorus content to be listed on the nutrition facts table of packaged food

products.

Further research is required to examine the discrepancies between the MPF subtypes

analyzed and the comparable CNF values (Appendix I). As the CNF should be a trusted source

of nutrient information, its accuracy is important to ensure patients are able to make appropriate

foods choices for their therapeutic dietary restrictions. While our study focused on MPF foods, it

would be interesting investigate other sources of protein and food groups known to contain

additives, such as commercially baked goods. In addition, as 21% of participants surveyed ate a

meal outside of the home at least 4-5 times per week, it would be important to analyze the

nutrient content commonly consumed fast-food items. Finally, as phosphorus and potassium

additives were less likely to be found in fresh MPF, future research is needed to examine

whether consuming a diet that consists of unprocessed, fresh foods leads to improved nutritional

markers and outcomes in CKD patients.

78

REFERENCES

AAFC: Agriculture and Agri-Food Canada. 2013. Sodium reduction efforts by the Canadian

Food Industry. Food regulatory issues division. [cited 2015 April 10] Available from:

www.agr.gc.caéfood-regulatory-issues

AAFC: Agriculture and Agri-Food Canada: Per Capita Consumption Poultry and Other

Animal Protein Sources Comparison. 2013. [cited March 15, 2015]. Available from:

http://www.agr.gc.ca/eng/industry-markets-and-trade/statistics-and-market-information/by-

product-sector/poultry-and-eggs/poultry-and-egg-market-information-canadian-

industry/industry-indicators/per-capita-consumption/?id=1384971854413

ADA & DC: American Dietetic Association & Dietitians of Canada. 2000. Manual of

Clinical Dietetics, 6th

edition. Chicago, Illinois, USA

Ahuja JK, Pehrsson PR, Haytowitz DB, Wasswa-Kintu S, Nickle M, Showell B, Thomas R,

Roseland J, Williams J, Khan M, Nguyen Q, Hoy K, Martin C, Rhodes D, Moshfegh A,

Gillespie C, Gunn J, Merritt R, Cogswell M. 2015. Sodium monitoring in commercially

processed and restaurant foods. American Journal of Clinical Nutrition 101(3), pp. 622-631

Albaaj F, Hutchison AJ. 2003. Hyperphosphatemia in Renal Failure: Causes, consequences,

and current management. Drugs 63(6), pp.577-496.

Allon M, Dansby L, Shanklin N. 1993. Glucose modulation of the disposal of an acute

potassium load in patients with end-stage renal disease. The Amercian Journal of Medicine

94:475-482

Arora P, Vasa P, Brenner D, Iglar K, McFarlane P, Morrison H, Badawi A. 2013. Prevalence

estimates of chronic kidney disease in Canada: results of a nationally representative survey.

Canadian Medical Association Journal 185(9), pp. 417-423

Barr S. 2010. Reducing dietary sodium intake: the Canadian context. Applied Physiology

Nutrition and Metabolism 35(1):1-8.

Bell RR, Draper HH, Tzeng DYM, Shin HK, Schmidt GR. 1977. Physiological responses of

human adults to foods containing phosphorus additives. The Journal of Nutrition 107(1), pp.

42-50.

Benini O, D’Alessandro C, Gianfaldoni D, Cupisti A. 2011. Extra-phosphate load from food

additives in commonly eaten foods: A real insidious danger for renal patients. Journal of

Renal Nutrition I21(4), pp. 303-308

Bertino M, Beauchamp GK, Moran M. 1982. Long-term reduction in dietary sodium alters

the taste of salt. American Journal of Clinical Nutrition. 36(6), pp. 1134-1144

Block GA, Hulbert-Shearon T, Levin NW, Port FK. 1998. Association of serum phosphorus

and calcium x phosphorus product with mortality risk in chronic hemodialysis patients: a

national study. American Journal of Kidney Diseases 31(4), pp. 607-617.

79

Boaz M, Smetana S. 1996. Regression equation predicts dietary phosphorus intake from

estimate of dietary protein intake. Journal of the American Dietetic Association. 96(12),

pp.1268-70

Braschi A, Gill L, Naismith DJ. 2009. Partial substitution of sodium with potassium in white

bread: feasibility and bioavailability. International Journal of Food Sciences and Nutrition

60(6), pp. 507-521

Bross R, Noori N, Kovesdy CP, Murali SB, Benner D, Block G, Kopple JD, Kalantar-Zadeh

K. 2010. Dietary assessment of individuals with chronic kidney disease. Seminars in dialysis

23(4), pp. 359-364.

Brown D. 2006. Do Food Frequency Questionnaires Have Too Many Limitations? Journal of

the American Dietetic Association 106(10), pp. 1541–1542

Byham-Gray L and Wiesen K. 2005. A clinical guide to nutrition care in kidney disease.

Renal dietitians dietetic practice group of the American Dietetic Association and the council

on renal nutrition of the National Kidney Foundation. USA

Cafferty J, Martin J, Marcus H, Wan C, Mulderrig K. 2014. Prevalence of Phosphate

Additives in Meat Products in Waterloo Region Grocery Stores. Journal of Renal Nutrition

24(2): 137

Caldeira D, Amaral T, David C, Sampaio C. 2011. Educational strategies to reduce serum

phosphorus in hyperphosphatemic patients with chronic kidney disease: systematic review

with meta-analysis. Journal of Renal Nutrition 21(4), pp. 285-294

Calvo MS, Uribarri J. 2013. Contributions to Total Phosphorus Intake: All Sources

Considered. Seminars in Dialysis 26(1), pp. 54-61

Calvo MS, Moshfegh AJ, Tucker KL. 2014. Assessing the health impact of phosphorus in the

food supply: Issues and considerations. Advances in Nutrition 5(1), pp. 104-113

Calvo MS, Park YK. 1996. Changing phosphorus content of the US diet: potential for

adverse effects on bone. Journal of Nutrition 126, pp.S1168–S1180

Calvo MS. 2000. Dietary considerations to prevent loss of bone and renal function. Nutrition

16(7-8), pp. 564-566

Carrero JJ, Stenvinkel P, Cuppari L, Ikizler TA, Kalantar-Zadeh K, Kaysen G, Mitch WE,

Price SR, Wanner C, Wang AY, Wee P, Franch HA. 2013. Etiology of the protein-energy

wasting syndrome in chronic kidney disease: a consensus statement from the International

Society of Renal Nutrition and Metabolism (ISRNM). Journal of Renal Nutrition. 23(2),

pp.77-90

Carrigan A, Klinger A, Choquette SS, Luzuriaga-McPherson A, Bell EK, Darnell B,

Gutierrez OM. 2014. Contribution of food additives to sodium and phosphorus content of

diets rich in processed foods. Journal of Renal Nutrition 24(1), pp. 13-19

80

CFIA: Canadian Food Inspection Agency. 2013. Solid cut meats which contain phosphate

salts and/or water. [cited December 20, 2013] Available from:

http://www.inspection.gc.ca/food/retail-food/information-bulletins/phosphate-

salts/eng/1331671950278/1331672020243

CFIA: Canadian Food Inspection Agency. 2014. Specific nutrient content claim

requirements. [cited March 31, 2015] Available from: http://www.inspection.gc.ca

CFIA: Canadian Food Inspection Agency. 2015a. Information within the nutrition facts table:

Additional nutritional information. [cited March 31, 2015] Available from:

http://www.inspection.gc.ca

CFIA: Canadian Food Inspection Agency. 2015b. Food Labelling for Industry. [Cited 2015

April 7]. Available from: http://www.inspection.gc.ca/food/labelling/food-labelling-for-

industry/eng/1383607266489/1383607344939

Chang AR, Lazo M, Appel LJ, Guiterrez OM, Grams ME. 2014. High dietary phosphorus

intake is associated with all-cause mortality: results from NHANES III. American Journal of

Clinical Nutrition 99, pp. 320-327

China Salt Substitute Study Collaborative Group. 2007. Salt substitution: a low-cost strategy

for blood pressure control among rural Chinese: A randomized, controlled trial. Journal of

Hypertension 25(10), pp.2011-2018.

Chiu YW, Teitelbaum I, Misra M, de Leon EM, Adzize T, Mehrotra R. 2009. Pill burden,

adherence, hyperphosphatemia and quality of life in maintenance dialysis patients. Clinical

Journal of the American Society of Nephrology 4(6), pp. 1089-1096.

CNF User’s Guide: Nutrition Research Division, Health Canada. Canadian Nutrient File

User’s guide. 2010. [cited May 10 2015] Available at http://www.hc-sc.gc.ca/fn-

an/nutrition/fiche-nutri-data/user_guide_d_utilisation01-eng.php

CNF: Health Canada. Canadian Nutrient File, 2010 version. [cited May 10 2015]. Available

at: http://www.hc-sc.gc.ca/fn-an/nutrition/fiche-nutri-data/index-eng.php

Cogswell ME, Zhang Z, Carriquiry AL, Gunn JP, Kuklina EV, Saydah SH, Yang Q,

Moshfegh AJ.2012. Sodium and potassium intakes among US adults: NHANES 2003-2008.

American Journal of Clinical Nutrition. 96(3), pp.647-57

CORR: Canadian Organ Replacement Register Annual Report: Treatment of End-Stage

Organ Failure in Canada, 2003 to 2012. 2014. Available at:

https://secure.cihi.ca/free_products/2014_CORR_Annual_Report_EN.pdf [Accessed: 21

March 2015]

Csizmadi I, Kahle L, Ullman R, Dawe U, Zimmerman TP, Friedenreich CM, Bryant H,

Subar AF. 2007. Adaptation and evaluation of the National Cancer Institute's Diet History

Questionnaire and nutrient database for Canadian populations. Public Health Nutrition 10(1),

pp.88-96

81

CTAC: Conseil de la transformation agroalimentaire et des produits de consummation. 2009.

Reformulation of products to reduce sodium: Salt reduction guide for the food industry.

Quebec: CTAC.

Curtis JC, Niederman SA, Kansagra SM. 2013. Availability of potassium on the nutrition

facts panel of US packaged foods. JAMA Internal Medicine 173(9), pp. 828-829

Cupisti A, Benini O, Ferretti V, Gianfaldoni D, Kalantar-Zadeh K. 2012. Novel differential

measurement of natural and added phosphorus in cooked ham with or without preservatives.

Journal of Renal Nutrition 22(6), pp. 533-540

Desmond E. 2006. Reducing salt: A challenge for the meat industry. Meat Science 74(1),

pp.188-196, 2006

DeWardener HE, MacGregor GA. 2002. Harmful effects of dietary salt in addition to

hypertension. Journal of Human Hypertension 16(4), pp. 213–23.

Dickinson HO, Nicolson DJ, Campbell F, Beyer FR, Mason J. 2006. Potassium

supplementation for the management of primary hypertension in adults. Cochrane Database

Systematic Reviews 19(3), pp. CD004641.

Dhingra R, Sullivan LM, Fox CS, Wang TJ, D’Agostino RB, Gaziano MJ, Ramachandaran

VS. 2007. Relations of serum phosphorus and calcium levels to the incidence of

cardiovascular disease in the community. Archives of Internal Medicine 167, pp. 879-885

Doorenbos CJ, Vermeij CG. 2003. Danger of salt substitutes that contain potassium in

patients with renal failure. British Medical Journal 326(7379), pp. 35-36

Dotsch M, Busch J, Batenburg M, Leim G, Tareius E, Mueller R, Meijer G. 2009. Strategies

to reduce sodium consumption: a food industry perspective. Critical review in food science

and nutrition. 49(10), pp. 841-851

Doyle ME, Glass KA. 2010. Sodium Reduction and Its Effect on Food Safety, Food Quality,

and Human Health. Comprehensive Reviews in Food Science and Food Safety 9(1), pp. 44–

56

Fassett RG, Robertson IK, Geraghty DP, Ball MJ, Coombes JS. 2007. Dietary intake of

patients with chronic kidney disease entering the LORD trial: Adjusting for underreporting.

Journal of Renal Nutrition 17(4), pp. 235-242

FCPC: Food and Consumer Products of Canada. 2011. Offering Canada more products with

reduced sodium. [cited 2015 April 27]. Available at:

http://www.fcpc.ca/Portals/0/Userfiles/PAResources/Public2014/HealthWellness_Report2.pd

f

FDA: Food and Drug Administration. 2013. Guidance for Industry: A Food Labeling Guide.

[cited April 28, 2015] Available at:

http://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/L

abelingNutrition/ucm2006828.htm

82

FDA: Food and Drug Administration. 2014a. Code of Federal Regulations Title 21 – Food

and Drugs, Part 184 Direct food substances affirmed as generally recognized as safe.

Department of Health and Human Services. [cited May 5, 2015]. Available at:

http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=184

FDA: Food and Drug Administration. 2014b. Code of Federal Regulations Title 21. [cited

April 28, 2015] Available at:

http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?fr=101.9

FDA: Food and Drug Administration. 2014c. Food Labeling: Revision of the Nutrition and

Supplement Facts Labels. Federal Regulations 79(41), pp. 11879 -11987

Fernandez J, Oster JF, Perez GO. 1986. Impaired extrarenal disposal of an acute oral

potassium load in patients with end-stage renal disease on chronic hemodialysis. Mineral and

Electrolyte Metabolism 12(2); pp. 125-129

Fischer PW, Vigneault M, Huang R, Arvaniti K, Roach P. 2009. Sodium food sources in the

Canadian diet. Applied Physiology Nutrition and Metabolism 34(5), pp. 884-892

Food and Nutrition Board, National Research Council, National Academy of Sciences:

Recommended Dietary Allowances. 10th

edition. 1989. Washington, DC, National Academy

Press, pp 52-77

Foque D, Kalantar-Zadeh K, Kopple JD, Cano N, Chauveau P, Cuppari L, Franch H,

Guarnieri G, Ikizler TA, Kaysen G, Lindholm B, Massy Z, Mitch W, Pineda E, Stenvinkel P,

Treviño-Becerra A, Wanner C. 2008. A proposed nomenclature and diagnostic criteria for

protein-energy wasting in acute and chronic kidney disease. Kidney International 73(4), pp.

391-398

Friedman EA. 2005. Consequences and management of hyperphosphatemia in patients with

renal insufficiency. Kidney International 67(S95), pp.S1-S7.

FSIS: Food Safety and Inspection Services. 2012. Code of Federal Regulations, Section

424.21. [cited May 5, 2015] Available at: http://www.gpo.gov/fdsys/granule/CFR-2012-

title9-vol2/CFR-2012-title9-vol2-sec424-21

FSIS: Food Safety and Inspection Services. 2014. Descriptive Designation for Raw Meat and

Poultry Products Containing Added Solutions. Federal Register 79(50).

FSIS: Food Safety and Inspection Services. 2015. Safe and suitable ingredients used in the

production of meat, poultry and egg products. 7120.1, Rev 26. [cited April 28, 2015]

Available at: http://www.fsis.usda.gov/wps/wcm/connect/bab10e09-aefa-483b-8be8-

809a1f051d4c/7120.1.pdf?MOD=AJPERES

Garriguet D. 2004. Nutrition: Findings from the Canadian Community Health Survey,

Overview of Canadians’ Eating Habits. Statistics Canada.

83

Gou P, Guerrero L, Gelabert J, Arnau J. 1995. Potassium chloride, potassium lactate and

glycine as sodium chloride substitutes in fermented sausages and in dry-cured pork loin.

Meat Science 42(1), pp. 37-48

Government of Canada. 2015. Safe internal cooking temperatures. [cited 2015 May 30].

Available at: http://healthycanadians.gc.ca/eating-nutrition/safety-salubrite/cook-

temperatures-cuisson-eng.php

Health Canada. 2004. Guide to Food Labelling and Advertising - Chapter 14. [Cited 2012

Feb 18]. Available from: http://www.inspection.gc.ca/english/fssa/labeti/guide/tab14e.shtml

Health Canada. 2008. Nutrient value of some common foods. [cited 2015, March 16]

Available at: http://www.hc-sc.gc.ca/fn-an/nutrition/fiche-nutri-data/nutrient_value-

valeurs_nutritives-tc-tm-eng.php

Health Canada. 2010. Sodium reduction strategy for Canadians, Recommendations of the

sodium working group. Nutrition Evaluation Division. [cited 2015 April 10]. Available from:

http://www.hc-sc.gc.ca/fn-an/nutrition/sodium/related-info-connexe/strateg/reduct-strat-

eng.php#a6

Health Canada. 2012a. Guidance for the Food Industry on Reducing Sodium in Processed

Foods. Bureau of Nutritional Sciences [cited 2015 April 10] Available from: http://www.hc-

sc.gc.ca/fn-an/legislation/guide-ld/2012-sodium-reduction-indust-eng.php

Health Canada. 2012b. Notice of Modification to the List of Permitted Preservatives to

Enable the Addition of Potassium Lactate and Sodium Lactate to Standardized Meat

Products and Poultry Meat Products. Bureau of chemical safety food directorate health

products and food branch. [cited 2015 April 1] Available from: http://www.hc-sc.gc.ca/fn-

an/consult/nom-adm-0001/index-eng.php

Health Canada. 2014. Health Canada`s proposal to enable the use of tripotassium phosphate

(potassium phosphate, tribasic), potassium tripolyphosphate, sodium potassium

tripolyphosphate, and sodium potassium hexametaphosphate in various standardized and

unstandardized foods. Bureau of chemical safety. [cited 2015 April 10]. Available at:

http://www.hc-sc.gc.ca/fn-an/consult/nop-adm-0008/document-consultation-eng.php

Health Canada. 2015a. Proposed food label changes to the nutrition facts table [cited August

31, 2015]. http://healthycanadians.gc.ca/health-system-systeme-sante/consultations/food-

label-etiquette-des-aliments/nutrition-facts-valeur-nutritive-eng.php

Health Canada. 2015b. Health Canada's Proposed Changes to the Daily Values (DVs) for

Use in Nutrition Labelling. [cited July 7, 2015] http://www.hc-sc.gc.ca/fn-an/consult/2014-

daily-value-valeurs-quotidiennes/document-consultation-eng.php#appe

Heeg JE, De Jong PE, Van Der Hem GK, Zeeuw D. 1989. Efficacy and variability of the

antiproteinuric effect of ACE inhibition by lisinopril. Kidney International. 36(2), pp. 272-

279

84

Henney JE, Taylor CL, Boon CS, editors. 2010. NIH sodium reduction strategy: Institute of

Medicine (US) Committee on Strategies to Reduce Sodium Intake in the United States.

Washington, DC, National Academies Press.

Holbrook JT, Patterson KY, Bodner JE, Douglas LW, Veillon C, Kelsay JL, Mertz W, Smith

JC. 1984. Sodium and potassium intake and balance in adults consuming self-selected diets.

American Journal of Clinical Nutrition 40(4):786-793

Hoy MK, Goldman JD. 2012. Potassium intake of the U.S. Population: What we eat in

America, NHANES 2009-2010. Food Surveys Research Group Dietary Data Brief No. 10.

[cited April 28, 2015] Available at: http://www.ars.usda.gov/Services/docs.htm?docid=19476

Ikizler TA, Flakoll PJ, Parker RA, Hakim RM. 1994. Amino acid and albumin losses during

hemodialysis. Kidney International 46(3):830-837

IOM: Institute of Medicine. 1997. Dietary Reference Intakes: Calcium, Phosphorus,

Magnesium, Vitamin D and Fluoride. Washington, DC: The National Academy Press

IOM: Institute of Medicine. 2005. Dietary Reference Intakes for Water, Potassium, Sodium,

Chloride, and Sulfate. Washington, DC: The National Academy Press

Jadeja YP, Kher V. 2012. Protein energy wasting in chronic kidney disease: An update with

focus on nutritional interventions to improve outcomes. Indian Journal of Endocrinology and

Metabolism 16(2), pp. 246-251

Jaffery JB, Hood VL. 2006. Conflicting dietary advice for adhering to low-sodium and low-

phosphorus diet. Journal of Renal Nutrition 16, pp. 332-336

Jamison RL. 2001. Hyperkalemia in the patient with end-stage renal disease. Nephrology

Rounds 4, pp. 1-6

John S, Rangan Y, Block C, Koff M. 2011. Life-threatening hyperkalemia from nutritional

supplements: uncommon or undiagnosed? American Journal of Emergency Medicine 29(9),

pp.1237.e1-1237.e2

K/DOQI: National Kidney Foundation Kidney Disease Outcomes Quality Initiative. 2000.

Clinical practice guidelines for nutrition in chronic renal failure. American Journal of Kidney

Diseases 35(6), pp. S1–140.

K/DOQI: National Kidney Foundation Kidney Disease Outcomes Quality Initiative. 2003.

Clinical practice guidelines for bone metabolism and disease in chronic kidney disease.

American Journal of Kidney Diseases 42(Suppl 3), pp. S1–S201, 2003

K/DOQI: National Kidney Foundation Kidney Disease Outcomes Quality Initiative. 2006.

Clinical Practice Guidelines for hemodialysis adequacy – update Guideline 5. American

Journal of Kidney Diseases 48(Suppl 1), pp. S2-S90

85

K/DOQI: National Kidney Foundation Kidney Disease Quality Outcomes Initiative. 2004.

Clinical practice guidelines on hypertension and antihypertensive agents in chronic kidney

disease. American Journal of Kidney Diseases 43(5 Suppl 1), pp.S1-290

Kalantar-Zadeh K, Block G, McAllister CJ, Humphreys MH, Kopple JD. 2004. Appetite and

inflammation, nutrition, anemia, and clinical outcome in hemodialysis patients. American

Journal Clinical Nutrition 80(2), pp. 299–307

Kalantar-Zadeh K, Gutekunst L, Mehrotra R, Kovesdy CP, Bross R, Shinaberger CS, Noori

N, Hirschberg R, Benner D, Nissenson AR, Kopple JD. 2010. Understanding sources of

dietary phosphorus in the treatment of patients with chronic kidney disease. Clinical Journal

of the Amercian Society of Nephrology 5, pp. 519-30.

Kalantar-Zadeh K, Kopple JD, Deepak S, Block D, Block G. 2002. Food intake

characteristics of hemodialysis patients as obtained by food frequency questionnaire. Journal

of Renal Nutrition 12(1), pp. 17-31

Kalantar-Zadeh K, Kovesdy CP, Bross R, Benner D, Noori N, Murali SB, Block T, Norris J,

Kopple JD, Block G. 2011. Design and development of a dialysis food frequency

questionnaire. Journal of Renal Nutrition 21(3), pp. 257-262

Kayikcioglu M, Tumuklu M, Ozkhaya M, Ozdogan O, Asci G, Duman S, Toz H, Can LH,

Basci A, Ok E. 2009. The benefit of salt restriction in the treatment of end-stage renal disease

by haemodialysis. Nephrology Dialysis Transplantation 24(3), pp. 956-962.

KDIGO: Kidney Disease: Improving Global Outcome. 2009. Clinical practice guideline for

the diagnosis, evaluation, prevention, and treatment of chronic kidney disease-mineral and

bone disorder (CKD-MBD) Kidney International 76(Suppl), pp. 1–130.

KDIGO: Kidney Disease: Improving Global Outcome. 2012. Clinical practice guideline for

the evaluation and management of chronic kidney disease. Kidney International Supplements

5(1), pp.73-90

Kearney PM, Whelton M, Reynolds K, Muntner P, Whelton PK, He J. 2005. Global burden

of hypertension: Analysis of worldwide data. Lancet 265(9455), pp. 217-223

Kendrick J, Chonchol M. 2011. The Role of Phosphorus in the Development and Progression

of Vascular Calcification. American Journal of Kidney Diseases 58(5), pp. 826-834.

Kestenbaum B, Sampson JN, Rudser KD, Patterson DJ, Seliger SL, Young B, Sherrard DJ,

Andress DL. 2005. Serum phosphate levels and mortality risk among people with chronic

kidney disease. Journal of the American Society of Nephrology 16(2), pp. 520-528.

Khoueiry G, Waked A, Goldman M, El-Charabaty E, Dunne E, Smith M, Kleiner M,

Lafferty J, Kalantar-Zadeh K, El-Sayegh S. 2011. Dietary intake in hemodialysis patients

does not reflect a heart healthy diet. Journal of Renal Nutrition 21(6), pp. 438-447.

Knochel JP. 2006. ‘Phosphorus’, in Modern Nutrition in Health and Disease, 10th

edition.

Baltimore, Lippincott Williams & Wilkins. pp, 211-222.

86

Koomans HA, Roos JC, Dorhout Mees EJ, Delawi IMK. 1985. Sodium balance in renal

failure: A comparison of patients with normal subjects under extremes of sodium intake.

Hypertension 7(50), pp. 714-721.

Kopple JD and Massry SG. 2004. Nutritional Management of Renal Disease. 2nd Edition,

Lippincott, Williams and Wilkins, Philadelphia

Kopple JD. 2001. The National Kidney Foundation K/DOQI Clinical Practice Guidelines for

Dietary Protein Intake for Chronic Dialysis. American Journal of Kidney Diseases 38(4), pp.

S68-S73

Kovesdy CP, Trivedi BK, Anderson JE. 2006. Association of kidney function with mortality

in patients with chronic kidney disease not yet on dialysis: A historical prospective cohort

study. Advances in Chronic Kidney Disease 13(2), pp. 183–188

Kuhlmann MK, Kribben A, Wittwer M and Ho WH. 2007. OPTA—malnutrition in chronic

renal failure. Nephrology Dialysis Transplant 22(Suppl 3), pp. iii13–iii19

Kuhlmann MK. 2010. Phosphate elimination in modalities of hemodialysis and peritoneal

dialysis. Blood Purification 29(2), pp. 137-144

Lampila LE. 1992. Functions and uses of phosphates in the seafood industry. Journal of

Aquatic Food Product Technology 1(3/4), pp. 29-41

Lampila LE. 2013. Applications and functions of food-grade phosphates. Annals of the New

York Academy of Sciences 1301, pp. 37-44

Leon JB, Sullivan CM, Sehgal AR. 2013. The prevalence of phosphorus-containing food

additives in top-selling foods in grocery stores. Journal of Renal Nutrition 23, pp. 265-270

Levey AS, De Jong PE, Coresh J, El Nahas M, Astor BC, Matsushita K, Gansevoort RT,

Kasiske BL, Eckardt KU. 2011. The definition, classification, and prognosis of chronic

kidney disease: a KDIGO controversies conference report. Kidney International. 80(1), pp.

17-28.

Li N, Prescott J, Wu Y, Barzi F, Yu X, Zhao L, Neal B; China Salt Substitute Study

Collaborative Group. 2009. The effects of a reduced-sodium, high-potassium salt substitute

on food taste and acceptability in rural northern China. British Journal of Nutrition

101(7):1088-1093

Lou-Arnal LM, Arnaudas-Casanova L, Caverni-Muñoz A, Vercet-Tormo A, Caramelo-

Gutiérrez R, Munguía-Navarro P, Campos-Gutiérrez B, García-Mena M, Moragrera B,

Moreno-López R, Bielsa-Gracia S, Cuberes-Izquierdo M; Grupo de Investigación ERC

Aragón. 2014. Hidden sources of phosphorus: presence of phosphorus-containing additives

in processed foods. Nefrologia 34(4), pp. 498-506

Macgregor Ga, Markandu ND, Sagnella GA, Singer DR, Carppuccio FP. 1989. Double-blind

study of three sodium intakes and long-term effects of sodium restriction in essential

hypertension. Lancet 2(8674), pp. 1244-1247

87

Mattes RD, Donnelly D. 1991. Relative contributions of dietary sodium sources. Journal of

the American College of Nutrition. 10(4), pp. 383-393

Mente A, O'Donnell MJ, Rangarajan S, McQueen MJ, Poirier P, Wielgosz A, Morrison H, Li

W, Wang X, Di C, Mony P, Devanath A, Rosengren A, Oguz A, Zatonska K, Yusufali AH,

Lopez-Jaramillo P, Avezum A, Ismail N, Lanas F, Puoane T, Diaz R, Kelishadi R, Iqbal R,

Yusuf R, Chifamba J, Khatib R, Teo K, Yusuf S; PURE Investigators. 2014. Association of

urinary sodium and potassium excretion with blood pressure. New England Journal of

Medicine 371(7), pp. 601-11

Miller P, Liu X, McMullen LM. 2015. Microbiota of regular sodium and sodium-reduced

ready-to-eat meat products obtained from the retail market. Canadian Journal of

Microbiology 61(2), pp.150-154.

Mintel International. 2009. Global Market Navigator Database. Mintel Group Ltd., Chicago,

Illinois.

Moe SM, Zidehsarai MP, Chambers MA, Jackman LA, Radcliff JS, Trevino LL, Donahue

SE, Asplin JR. 2011. Vegetarian compared with meat dietary protein source and phosphorus

homeostasis in chronic kidney disease. Clinical Journal of the American Society of

Nephrology 6(2), pp. 257-264

Mohan S, Campbell NRC, Willis K. 2009. Effective population-wide public health

interventions to promote sodium reduction. Canadian Medical Association Journal 181, pp.

605-609

Moubarac JC, Batal M, Martins AP, Claro R, Levy RB, Cannon G, Monteiro C. 2014.

Processed and ultra-processed food products: consumption trends in Canada from 1938 to

2011. Canadian Journal of Dietetic Practice and Research 75(1), pp. 15-21

Murphy-Gutekunst L, Uribarri J. 2005. Hidden phosphorus-enhanced meats: Part 3. Journal

of Renal Nutrition 15(4), pp. E1-E4

Murphy-Gutekunst L. 2005. Hidden phosphorus in popular beverages: part 1. Journal of

Renal Nutrition 15(2), pp: e1-e6.

Navaneethan SD, Palmer SC, Craig JC, Elder GJ, Strippoli GF. 2009. Benefits and harms of

phosphate binders in CKD: a systematic review of randomized controlled trials. American

Journal of Kidney Disease 54(4), pp.619-637.

Nelms MN, Sucher KP, Lacey K, Roth SL. 2007. Nutrition Therapy & Pathophysiology, 2nd

ed. Belmont CA: Wadsworth Centgage Learning

Nerbass FB, Pecoits-Filho R, McIntyre NJ, McIntyre CW, Willingham FC, Taal MW. 2014.

Demographic associations of high estimated sodium intake and frequency of consumption of

high sodium foods in people with chronic kidney disease stage 3 in England. Journal of

Renal Nutrition 24(4), pp. 236-242

88

NKF: National Kidney Foundation: Sodium and Your CKD Diet: How to Spice Up Your

Cooking Available at https://www.kidney.org/atoz/content/sodiumckd accessed February 23,

2015

Noori N, Kalantar-Zadeh K, Kovesdy CP, Murali SB, Bross R, Nissenson A, Kopple JD.

2010. Dietary potassium intake and mortality in long term hemodialysis patients. American

Journal of Kidney Diseases 56(2), pp. 338-347

Noori N, Sims JJ, Kopple JD, Shah A, Shah A, Colman S, Shinaberger CS, Bross R,

Mehrotra R, Kovesdy CP, Kalantar-Zadeh K. 2010. Organic and inorganic dietary

phosphorus and its management in chronic kidney disease. Iranian Journal of Kidney

Diseases 4(2), pp. 89-100

Olson DG. 1982. Salt for processing probably can be cut by only one quarter. The National

Provisioner 17, pp. 7-10

ORN: Ontario Renal Network. 2013. Chronic Kidney Disease Nutrition Fact Sheets. [Cited

March 31 2015] Available from:

http://www.renalnetwork.on.ca/common/pages/UserFile.aspx?fileId=266411

Palmer BF. 2014. Regulation of Potassium Homeostasis. Clinical Journal of the American

Society of Nephrology Published online before print doi: 10.2215/CJN.08580813

Palmer SC, Hayen A, Macaskill P, Pellegrini F, Craig JC, Elder F, Strippoli GFM. 2011.

Serum levels of phosphorus, parathyroid hormone, and calcium and risks of death and

cardiovascular disease in individuals with chronic kidney disease. Journal of the American

Medical Association 203(11), pp. 1119-1127

Palmer SC, McGregor DO, Macaskill P, Craig JC, Elder GJ, Strippoli GF. 2007.

Metaanalysis: vitamin D compounds in chronic kidney disease. Annals of Internal Medicine

147(12), pp.840-853.

Pasiakos SM, Agarwal S, Lieberman HR, Fulgoni VL. 2015. Sources and amounts of animal,

dairy and plant protein intake of US adults in 2007-2010. Nutrients 7(8), pp. 7058-7069

Penz Ed, Joffres MR, Campbell NR. 2008. Reducing dietary sodium and decreases in

cardiovascular disease in Canada. Canadian Journal of Cardiology 26(6), pp. 497-501

Putcha N, Allon M. 2007. Management of hyperkalemia in dialysis patients. Seminars in

dialysis. 20(5), pp. 431-439

Ray KK, Dorman S, Watson RDS. 1999. Severe hyperkalemia due to the concomitant use of

salt substitutes and ACE inhibitors in hypertension: A potentially life threatening interaction.

Journal of Human Hypertension 13(10), pp. 717-720

Ritz E, Koleganova N, Piecha G. 2009. Role of sodium intake in the progression of chronic

kidney disease. Journal of renal nutrition 19(1), pp. 61-62.

89

Rosenberg M. 2013. Overview of the management of chronic kidney disease in adults.

Available at: www.uptodate.com [Accessed: 21 March 2015]

Ruusunen M, Niemisto M, Puolanne E. 2002. Sodium reduction in cooked meat products by

using commercial potassium phosphate mixtures. Agricultural and food science in Finland

11(1), pp. 199-207

Sacks FM, Svetkey LP, Vollmer WM, Appel LJ, Bray GA, Harsha D, Obarzanek E, Conlin

PR, Miller ER 3rd, Simons-Morton DG, Karanja N, Lin PH; DASH-Sodium Collaborative

Research Group. 2001. Effects on blood pressure of reduced dietary sodium and the Dietary

Approaches to Stop Hypertension (DASH) diet. New England Journal of Medicine 344 (1):3-

10

Salehi-Abargouei A1, Maghsoudi Z, Shirani F, Azadbakht L. 2013. Effects of Dietary

Approaches to Stop Hypertension (DASH)-style diet on fatal or nonfatal cardiovascular

diseases--incidence: a systematic review and meta-analysis on observational prospective

studies. Nutrition 29, pp. 611-8

Sanghavi S, Whiting S, Uribarri J. 2013. Potassium balance in dialysis patients. Seminars in

dialysis. 26(5), pp. 597-603

Sarnak MJ, Levey AS. 2000. Epidemiology, diagnosis, and management of cardiac disease in

chronic renal disease. Journal of Thrombosis and Thrombolysis 10 (2), pp.169–180

Schermel A, Emrich TE, Arcand J, Wong CL, L'Abbé MR. 2013. Nutrition marketing on

processed food packages in Canada: 2010 Food Label Information Program. Applied

Physiology, Nutrition, and Metabolism 38(6), pp. 666-672

Sherman RA, Mehta DO. 2009a. Dietary phosphorus restriction in dialysis patients: Potential

impact of processed meat, poultry and fish products as protein sources. American Journal of

Kidney Diseases 54(1), pp.18-23

Sherman RA, Mehta DO. 2009b. Phosphorus and potassium content of enhanced meat and

poultry products: Implications for patients who receive dialysis. Clinical Journal of the

American Society of Nephrology 4(8), pp.1370-1373

Sherman RA, Mehta O. 2009. Potassium in Food Additives, Something else to consider.

Journal of Renal Nutrition. 19 60, pp. 441, 442

Sherman RA. 2007. Dietary phosphate restriction and protein intake in dialysis patients: a

misdirected focus. Seminars in Dialysis 20(1), pp.16-18.

Shinaberger CS, Greenland S, Kopple JD, Van Wyck D, Mehrotra R, Kovesdy CP, Kalantar-

Zadeh K. 2008. Is controlling phosphorus by decreasing dietary protein intake beneficial or

harmful in persons with kidney disease? American Journal of Clinical Nutrition. 88(6), pp.

1511-1518

90

Shults GW, Russell DR, Wierbicki E. 1972. Effect of condensed phosphates on pH, swelling

and water holding capacity of beef. Journal of Food Sciences 37(6), pp 860-864

Slagman MC, Waanders F, Hemmelder MH, Woittiez AJ, Janssen WM, Lambers Heerspink

HJ, Navis G, Laverman GD; HOlland NEphrology STudy Group. 2011. Moderate dietary

sodium restriction added to angiotensin converting enzyme inhibition compared with dual

blockade in lowering proteinuria and blood pressure: randomised controlled trial. British

Medical Journal. 2011 343, pp. d4366

Statistics Canada. Canadian Community Health Survey (CCHS) 2.2, Nutrition. 2004 [cited

2010 Mar 25]. Available from: http://www.statcan.gc.ca/cgi-

bin/imdb/p2SV.pl?Function=getSurvey&SDDS=5049&lang=en&db=imdb&adm=8&dis=2

Statistics Canada. 2011. The 10 leading causes of death. [cited July 7 2015]. Available at:

http://www.statcan.gc.ca/pub/82-625-x/2014001/article/11896-eng.htm

Strippoli GFM, Palmer SC, Tong A, Elder G, Messa P, Craig JC. 2006. Metaanalysis of

biochemical and patient-level effects of calcimimetic therapy. American Journal of Kidney

Disease 47(5), pp. 715-726.

Subar AF, Thompson FE, Kipnis V, Midthune D, Hurwitz P, McNutt S, McIntosh A,

Rosenfeld S. 2001. Comparative validation of the Block, Willett, and National Cancer

Institute food frequency questionnaires : the Eating at America's Table Study. American

Journal of Epidemiology 154(12), pp.1089-1099.

Sullivan C, Sayre SS, Leon JB, Machekano R, Love TE, Porter D, Marbury M, Sehgal AR.

2009. Effect of food additives on hyperphosphatemia among patients with end-stage renal

disease: a randomized controlled trial. Journal of the American Medical Association 301(6),

pp. 629-35

Sullivan CM, Leon JB, Sehgal AR. 2007. Phosphorus-containing food additives and the

accuracy of nutrient databases: Implications for renal patients. Journal of Renal Nutrition

17(5), pp. 350-354.

Tanase SM, Koski KG, Laffey, PJ, Cooper MJ, Cockell KA. 2011. Canadians continue to

consume too much sodium and not enough potassium. Canadian Journal of Public Health

102(3), pp. 164-168

Tomiyama C, Higa A, Dalboni MA, Cendoroglo M, Draibe SA, Cuppari L, Carvalho AB,

Neto EM, Canziani ME. 2006. The impact of traditional and non-traditional risk factors on

coronary calcification in pre-dialysis patients. Nephrology Dialysis Tranplantation. 21(9),

pp. 2464-2471.

Tonelli M, Sacks F, Pfeffer M, Gao Zhiwi, Curham G. 2005. Relation between sersum

phosphate and cardiovascular event rate in people with coronary disease. Circulation 112,

pp. 2627-2633

91

U.S. Department of Health and Human Services. 2005. Dietary guidelines for Americans.

[cited April 30, 2015] Available at:

http://www.health.gov/dietaryguidelines/dga2005/document/html/chapter8.htm

Uribarri J, Calvo MS. 2003. Hidden sources of phosphorus in the typical American diet:

Does it matter in nephrology? Seminars in Dialysis 16(3), pp. 186-188.

Uribarri J. 2007. Phosphorus homeostasis in normal health and in chronic kidney disease

patients with special emphasis on dietary phosphorus intake. Seminars in dialysis 20(4), pp.

295-301

USDA: United States Department of Agriculture. 2007. Are any additives exempt from the

approval process? [cited April 9, 2015]. Available at:

http://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-

safety-fact-sheets/food-labeling/additives-in-meat-and-poultry-products/additives-in-meat-

and-poultry-products

USDA: United States Department of Agriculture. 2010. Can approved phosphates be

collectively designated as “sodium phosphates” or “potassium phosphates”, as the case may

be? [cited April 9, 2015]. Available at:

http://askfsis.custhelp.com/app/answers/detail/a_id/461/~/can-approved-phosphates-be-

collectively-designated-as-sodium-phosphates-or

USRDS: United States Renal Data System. 2003. Annual data report: atlas of end-stage

renal disease in the United States. Bethesda, MD: National Institutes of Health, National

Institute of Diabetes and Digestive and Kidney Diseases

Vennegoor MA. 2009. Salt restriction and practical aspects to improve compliance. Journal

of Renal Nutrition 19(1), pp. 63-68

Verhave JC, Hillege HL, Burgerhof JG, Janssen WM, Gansevoort RT, Navis GJ, DeZeeuw

D, De Jon PE. 2004. Sodium intake affects urinary albumin excretion especially in

overweight subjects. Journal of Internal Medicine 256(4), pp. 324-330

Verma AK, Banerjee R. 2012. Low-sodium meat products: retaining salty taste for sweet

health. Critical review in food science and nutrition. 52(1), pp. 72-84

Webster J, Trieu K, Dunford E, Hawkes C. 2014. Target Salt 2025: A global overview of

national programs to encourage the food industry to reduce salt in foods. Nutrients 6(8), pp.

3274-3287

Weir MR, Fink JC. 2005. Salt intake and progression of chronic kidney disease: an

overlooked modifiable exposure? A commentary. American Journal of Kidney Diseases

45(1), pp. 176

92

Whaley-Connell AT, Sowers JR, Stevens LA, McFarlane SI, Shlipak MG, Norris KC, Chen

SC, Qiu Y, Wang C, Li S, Vassalotti JA, Collins AJ, Kidney Early Evaluation Program

Investigators. 2008. CKD in the United States: Kidney Early Evaluation Program (KEEP)

and National Health and Nutrition Examination Survey (NHANES) 1999-2004. American

Journal of Kidney Diseases 51(4 Suppl 2), pp. S13

Wong CL, Arcand J, Mendoza J, Henson SJ, Qi Y, Lou W, L'Abbé MR. 2013. Consumer

attitudes and understanding of low-sodium claims on food: an analysis of healthy and

hypertensive individuals. American Journal of Clinical Nutrition 97(6), pp.1288-98.

Wright JA, Cavanaugh KL. 2010. Dietary sodium in the chronic kidney disease: A

comprehensive approach. Seminars in Dialysis 23(4), pp. 415-421

93

APPENDICES

Appendix A – Food Questionnaire

94

Food Questionnaire

Study Title: The phosphorus and potassium content of frequently consumed

types of meat, poultry and fish items among patients with end-stage renal

disease

Participant ID # ___________

Date: ___________

ABOUT THIS SURVEY

We are asking you to complete this form to find out more about the

foods you have eaten at home, during the past month?

It will take approximately 25-35 minutes to complete. Please answer

each question as best you can and ask for help from the person who

shops and cooks most often in your home. Estimate if you aren’t

sure. Ask a research staff if you are unclear about a question.

1a) How often did you eat chicken that is NOT breaded (such as

breast, thighs, wings or drumsticks)?

□ NEVER (GO TO QUESTION 2)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

1b) Each time you ate chicken, how much did you usually eat?

□ Less than 1 breast or thigh or less than 2 wings or drumsticks

□ 1 breast or thigh or 2 drumsticks or wings

□ More than 1 breast or thigh or more than 2 drumsticks or wings

95

1c) How do you usually buy chicken? (Check all that apply)

□ Fresh, packaged □ Fresh, from butcher or meat counter

□ Frozen, packaged □ Rotisserie, cooked

□ I don’t know □ Other (please

explain):_____________________

1d) If you buy a specific brand of chicken most often, please state this

brand: ____________________________________________

2a) How often did you eat breaded chicken (including nuggets,

breaded wings, breaded burgers and chicken fingers)?

□ NEVER (GO TO QUESTION 3)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

2b) Each time you ate breaded chicken, how much did you usually

eat?

□ Less than 1 patty or less than 4 nuggets or less than 2 wings

□ 1 patty or 4-8 nuggets or 2 wings

□ More than 1 patty or more than 8 nuggets or more than 2 wings

2c) How do you usually buy your breaded chicken?

□ Frozen / Packaged

□ I buy fresh chicken that I coat in breadcrumbs myself

□ I don’t know □ Other (please

explain):_____________________

96

2d) If you buy a specific brand of breaded chicken most often, please

state this brand:

3a) How often did you eat turkey (such as roast turkey or turkey

cutlets)?

□ NEVER (GO TO QUESTION 4)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

3b) Each time you ate turkey, how much did you usually eat?

Note: 3 oz is about the size of a deck of cards

□ Less than 2 ounces

□ 2 to 5 ounces

□ More than 5 ounces

3c) How do you usually buy turkey?

□ Fresh, packaged □ Fresh, from butcher or meat counter

□ Frozen, packaged □ I don’t know

□ Other (please explain):_____________________

3d) If you buy a specific brand of turkey most often, please state this

brand:

97

4a) How often did you eat turkey cold cuts or chicken cold cuts (such

as luncheon meat, turkey ham, turkey salami or turkey pastrami?)

□ NEVER (GO TO QUESTION 5)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

4b) Each time you ate turkey or chicken cold cuts, how much did you

usually eat?

□ Less than 1 slice

□ 1 to 3 slices

□ More than 3 slices

4c) How do you usually buy your turkey or chicken cold cuts?

□ Pre-packaged □ From the deli counter □ I don’t

know

□ Other (please explain):_____________________

4d) If you buy a specific brand of turkey or chicken cold cuts most

often, please state this brand:

98

5a) How often did you eat luncheon ham or deli-style ham

□ NEVER (GO TO QUESTION 6)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

5b)Each time you ate luncheon ham or deli-style ham, how much did

you usually eat?

□ Less than 1 slice

□ 1 to 3 slices

□ More than 3 slices

5c) How do you usually buy your luncheon ham or deli-style ham?

□ Pre-packaged □ From the deli counter □ I don’t

know

□ Other (please explain):_____________________

5d) If you buy a specific brand of luncheon ham or deli-style ham

most often, please state this brand:

99

6a) How often did you eat other cold cuts or luncheon meats (such as

bologna, salami, corned beef, pastrami and others)?

□ NEVER (GO TO QUESTION 7)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

6b)Each time you ate other cold cuts or luncheon meats, how much

did you usually eat?

□ Less than 1 slice

□ 1 to 3 slices

□ More than 3 slices

6c) How do you usually buy your cold cuts or luncheon meats?

□ Pre-packaged □ From the deli counter □ I don’t

know

□ Other (please explain):_____________________

6d) If you buy a specific brand of cold cuts or luncheon meats most

often, please state this brand:

100

7a) How often did you eat beef hamburgers that were NOT from a fast

food or other restaurant?

□ NEVER (GO TO QUESTION 8)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

7b) Each time you ate beef hamburgers, how much did you usually

eat?

□ Less than 1 patty or less than 2 ounces

□ 1 patty or 2 to 4 ounces

□ More than 1 patty or more than 4 ounces

7c) How do you usually buy your beef hamburgers?

□ Frozen / Packaged □ Homemade hamburgers from fresh ground

beef

□ I don’t know □ Other (please

explain):_____________________

7d) If you buy a specific brand of beef hamburgers most often, please

state this brand:

101

8a) How often did you eat roast beef, pot roast, steak or other forms

of beef? (We will ask about ground beef and steak later on)

□ NEVER (GO TO QUESTION 9)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

8b) Each time you ate beef, how much did you usually eat?

Note: 3 oz is about the size of a deck of cards

□ Less than 2 ounces

□ 2 to 6 ounces

□ More 6 ounces

8c) How do you usually buy your beef?

□ Fresh, packaged □ Fresh, from butcher or meat counter

□ Frozen, packaged □ I don’t know

□ Other (please explain):_____________________

8d) If you buy a specific brand of beef most often, please state this

brand:

102

9a) How often did you eat steak (beef)?

□ NEVER (GO TO QUESTION 10)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

9b) Each time you ate steak, how much did you usually eat?

Note: 3 ounces is about the size of a deck of cards

□ Less than 3 ounces

□ 3 to 7 ounces

□ More than ounces

9c) How do you usually buy steak?

□ Fresh, packaged □ Fresh, from butcher or meat counter

□ Frozen, packaged □ I don’t know

□ Other (please explain):_____________________

9d) If you buy a specific brand of steak most often, please state this

brand:

103

10a) How often did you eat ground beef in mixtures (such as

meatballs, casseroles, chili or meatloaf)?

□ NEVER (GO TO QUESTION 11)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

10b) Each time you ate ground beef in mixtures, how much did you

usually eat?

□ Less than 3 ounces or less than ½ cup

□ 3 to 8 ounces or ½ cup to 1 cup

□ More than 8 ounces or more than 1 cup

10c) How do you usually buy ground beef in mixtures?

□ Frozen, packaged □ Fresh ground beef used in homemade

mixture

□ I don’t know □ Other (please

explain):_____________________

10d) If you buy a specific brand of ground beef in mixtures most

often, please state this brand:

104

11a) How often did you eat pork spareribs or beef spareribs?

□ NEVER (GO TO QUESTION 12)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

11b) Each time you ate spareribs, how much did you usually eat?

□ Less than 4 ribs

□ 4 to 12 ribs

□ More than 12 ribs

11c) How do you usually buy your spareribs?

□ Fresh, packaged □ Fresh, from meat counter

□ Frozen, packaged □ I don’t know

□ Other (please explain):_____________________

11d) If you buy a specific brand of spareribs most often, please state

this brand:

105

12a) How often did you eat pork (including chops, roasts, and in

mixed dishes)?

□ NEVER (GO TO QUESTION 13)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

12b) Each time you ate pork, how much did you usually eat?

Note: 3 ounces is about the size of a deck of cards

□ Less than 1 ounce

□ 1 to 3 ounces

□ More 3 ounces

12c) How do you usually buy your pork?

□ Fresh, packaged □ Fresh, from meat counter

□ Frozen, packaged □ I don’t know

□ Other (please explain):_____________________

12d) If you buy a specific brand of pork most often, please state this

brand:

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13a) How often did you eat baked ham or ham steak?

□ NEVER (GO TO QUESTION 14)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

13b) Each time you ate baked ham or ham steak, how much did you

usually eat? Note: 3 ounces is about the size of a deck of cards

□ Less than 1 ounce

□ 1 to 3 ounces

□ More 3 ounces

13c) How do you usually buy your baked ham or ham steak?

□ Packaged, cooked □ Meat counter, cooked □ Canned

□ I don’t know □ Other (please

explain):_____________________

13d) If you buy a specific brand of baked ham or ham steak most

often, please state this brand:

14a) How often did you eat bacon?

□ NEVER (GO TO QUESTION 15)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

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14b) Each time you ate bacon, how much did you usually eat?

□ Fewer than 2 slices

□ 2 to 4 slices

□ More than 4 slices

14c) How do you usually buy your bacon?

□ Fresh, packaged □ Fresh, from meat counter

□ I don’t know

□ Other (please explain):___________________

14d) If you buy a specific brand of bacon most often, please state this

brand:

15a) How often did you eat sausage? (Please do not include hot dogs,

wieners or frankfurters)

□ NEVER (GO TO QUESTION 16)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

15b) Each time you ate sausage, how much did you usually eat?

□ Less than 2 small links or less than 1 large link

□ 2 to 5 small links or 1 to 2 large links

□ More than 5 small links or more than 2 large links

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15c) How do you usually buy sausage?

□ Fresh, packaged □ Fresh, from deli counter □ I don’t

know

□ Frozen, packaged □ Other (please

explain):_____________________

15d) If you buy a specific brand of sausage most often, please state

this brand:

__________________________________________________________

16a) How often did you eat hot dogs, wieners or frankfurters?

□ NEVER (GO TO QUESTION 17)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

16b)Each time you ate hot dogs, wieners or frankfurters, how much

did you usually eat?

□ Less than 1 hot dog

□ 1 to 2 hot dogs

□ More than 2 hot dogs

16c) How do you usually buy hot dogs, wieners or frankfurters?

□ Fresh, packaged □ Fresh, from deli counter

□ Frozen, packaged □ I don’t know

□ Other (please explain):_____________________

109

16d) If you buy a specific brand hot dogs, wieners and frankfurters

most often, please state this brand:

17a) How often did you eat canned tuna (including in salads,

sandwiches or casseroles)?

□ NEVER (GO TO QUESTION 18)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

17b) Each time you ate canned tuna, how much did you usually eat?

□ Less than ¼ cup or less than 2 ounces

□ ¼ to ½ cup or 2 to 3 ounces

□ More than ½ cup or more than 3 ounces

17c) If you buy a specific brand of canned tuna most often, please

state this brand:

110

18a) How often did you eat canned salmon (including in salads,

sandwiches or casseroles)?

□ NEVER (GO TO QUESTION 19)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

18b) Each time you ate canned salmon, how much did you usually eat

□ Less than ¼ cup or less than 2 ounces

□ ¼ to ½ cup or 2 to 3 ounces

□ More than ½ cup or more than 3 ounces

18c) If you buy a specific brand of canned salmon most often, please

state this brand:

19a) How often did you eat dark or oily fish like salmon, fresh tuna,

trout, or mackerel that is NOT breaded, canned or smoked?

□ NEVER (GO TO QUESTION 20)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

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19b) Each time you ate dark or oily fish, how much did you usually

eat?

□ Less than 2 ounces or less than 1 fillet

□ 2 to 6 ounces or 1 fillet

□ More than 6 ounces or more than 1 fillet

19c) How do you usually buy dark or oily fish?

□ Fresh, packaged □ From seafood counter

□ Frozen, packaged □ I don’t know

□ Other (please explain):_____________________

19d) If you buy a specific brand of dark or oily fish most often, please

state this brand:

___________________________________________________________

20a) How often did you eat white or lean fish like cod, haddock, perch

or sole that is NOT breaded, canned or smoked?

□ NEVER (GO TO QUESTION 21)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

20b) Each time you ate white or lean fish, how much did you usually

eat?

□ Less than 2 ounces or less than 1 fillet

□ 2 to 6 ounces or 1 fillet

□ More than 6 ounces or more than 1 fillet

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20c) How do you usually buy white or lean fish?

□ Fresh, packaged □ From seafood counter

□ Frozen, packaged □ I don’t know

□ Other (please explain):_____________________

20d) If you buy a specific brand of white or lean fish most often,

please state this brand:

____________________________________________________________

21a) How often did you eat shrimp?

□ NEVER (GO TO QUESTION 22)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

21b) Each time you ate shrimp, how much did you usually eat?

Note: 1 ounce is about 4 medium-sized shrimp

□ Less than 1 ounce

□ 1 to 4 ounces

□ More than 4 ounces

21c) How do you usually buy shrimp?

□ From seafood counter □ Frozen, packaged, not breaded

□ Frozen, packaged, breaded □ I don’t know

□ Other (please explain):_____________________

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21d) If you buy a specific brand of shrimp most often, please state

this brand:

22a) How often did you eat other shellfish (such as crab, lobster or

scallops)?

□ NEVER (GO TO QUESTION 23)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

22b) Each time you ate shellfish, how much did you usually eat?

□ Less than 1 ounce

□ 1 to 4 ounces

□ More than 4 ounces

22c) How do you usually buy shellfish?

□ From seafood counter □ Frozen, packaged

□ I don’t know

□ Other (please explain):_____________________

22d) If you buy a specific brand of shellfish most often, please state

this brand:

114

23a) How often did you eat battered/breaded fish or fish sticks?

□ NEVER (GO TO QUESTION 24)

□ 1 time in the past month □ 3-4 times per week

□ 2-3 times in the past month □ 5-6 times per week

□ 1 time per week □ 1 time per day

□ 2 times per week □ 2 or more times per day

23b) Each time you ate battered/breaded fish or fish sticks, how much

did you usually eat?

□ Less than 2 ounces or less than 1 fillet

□ 2 to 6 ounces or 1 fillet

□ More than 6 ounces or more than 1 fillet

23c) How do you usually buy battered/breaded fish or fish sticks?

□ Frozen, packaged □ Fresh fish that I bread or batter myself

□ I don’t know

□ Other (please explain):_____________________

23d) If you buy a specific brand of battered/breaded fish or fish sticks

most often, please state this brand:

____________________________________________________________

24) Is there any other type of meat, poultry or fish product that you

ate, that was not included in the previous questions?

____________________________________________________________

115

25) At which grocery store(s) do you shop? (Check all that apply)

□ Sobey’s □ Metro

□ Loblaws □ Costco

□ No Frills □ Great Canadian Superstore

□ Other _____________________________

26) Who usually does the grocery shopping at home?

□ You □ Spouse / Partner □ Children □ Caregiver / Parent

□ Other _______________________

27) Who usually does the cooking at home?

□ You □ Spouse / Partner □ Children □ Caregiver / Parent

□ Other _______________________

28) During the past month, how often did you eat a meal outside of

the home (includes restaurants, fast food, coffee shops)?

□ More than once a day □ Once a day □ 4-5 times per week

□ 2-3 times per week □ 1-2 times per week □ 2-3 times per month

□ Once per month □ Less than once per month

29) If you are asked to follow a low phosphorus diet, do you think you

are following it?

□ I am not asked to follow a low phosphorus diet

□ I try to follow a low phosphorus diet and I usually do

□ I try to follow a low phosphorus diet, but I don’t always follow it

□ I don’t follow a low phosphorus diet

□ I don’t know what a low phosphorus diet is

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30) If you are asked to follow a low potassium diet, do you think you

are following it?

□ I am not asked to follow a low potassium diet

□ I try to follow a low potassium diet and I usually do

□ I try to follow a low potassium diet, but I don’t always follow it

□ I don’t follow a low potassium diet

□ I don’t know what a low potassium diet is

31) If you read the Nutrition Facts table (see picture) to

find out about the nutritional content of the food, what

do you usually look for? (check all that apply)

□ Calories □ Sodium □ Fat

□ Protein □ Phosphorus □ Potassium

□ Carbohydrate □ Sugar □ Fiber

□ I don’t read the nutrition facts table □ I don’t

know

32) Do you use the salt substitute called NoSalt©, NuSalt© or HalfSalt©,

when you cook?

□ I often use a salt substitute □ I sometimes use a salt substitute

□ I never use a salt substitute □ I don’t know

33) If you read the list of ingredients of the food you buy, what do you

usually look for? (check all that apply)

□ I don’t read the ingredient list

□ Ingredients with the word “phosphorus” or letters “phos”

□ Ingredients with the word “potassium”

□ Other ingredient (please specify): ______________________________

117

34) How often do you try to choose foods that say “Sodium-Free” or

“No Sodium” or “No Added Salt” on the food package?

□ Most of the time □ Some of the time □ Never □ I don’t know

35) How often do you try to choose foods that say “Reduced in

Sodium” or “25% Less Sodium” or “Lightly Salted” or “Lower in

Sodium” on the package?

□ Most of the time □ Some of the time □ Never □ I don’t know

Demographic Information

Reminder: All information given here and throughout the

questionnaire, will be kept confidential

36) Where do you live?

□ House □ Apartment □ Nursing Home □ Other: __________

37) How many people do you live with?

□ No one else □ 1 □ 2 □ 3 □ 4 or more

38) What is your highest level of education obtained?

□ Elementary School □ Some high school

□ High school diploma □ Some university / college

education

□ University / college degree □ Graduate education

□ None

118

39) Please identify your ethnic origin? (Sample geographic

backgrounds in brackets). Check all that apply:

□ Aboriginal (Inuit, First Nations, Metis, Aborigine, Maori)

□ African / Black (Afro-Caribbean, Kenyan, Ethiopian, Moroccan, Nigerian,

Egyptian)

□ Australasian / Pacific Islander (Australia, New Zealander, Fijian,)

□ Caribbean (Jamaican, Antiguan, Trinidadian)

□ Central Asian (Uzbeck, Afghan)

□ East Asian (Chinese, Japanese, Korean)

□ Caucasian / White / European (British, French, Greek, Italian, Russian)

□ Latin American (Brazilian, Peruvian, Nicaraguan, Mexican, Argentinean)

□ Middle Eastern / West Asian (Israeli, Palestinian, Armenian, Iraqi,

Iranian)

□ South Asian (Indian, Indo-Caribbean, Pakistani, Sri Lankan)

□ South-East Asian (Filipino, Laotian, Vietnamese)

□ Unknown

□ Other, please specify _________________________________________

40) What is your household annual income before taxes from all

sources?

□ Greater than $100,000

□ $80,000 – less than $100,000

□ $60,000 – less than $80,000

□ $40,000 – less than $ 60,000

□ $20,000 – less than $40,000

□ Less than $20,000

□ No income

119

Appendix B – Face Validation Recruitment Pre-Amble

Food Questionnaire

120

Study Title: The phosphorus and potassium content of frequently consumed types of meat, poultry and fish items

among patients with end-stage renal disease

Face Validation Recruitment Pre-Amble

RGM = Research Group Member RGM: I would like your help in making a questionnaire for a dialysis nutrition

study. The questionnaire is about which types of meat, poultry and fish products you eat at home most often. It will also include questions about how you or your primary caregiver purchase and prepare foods and some general questions about you. This information will help us learn more about what you eat, so we can study these foods in more detail.

Would you like to hear more about how you can help us with the

questionnaire?

Patient: Yes or No RGM: IF NO: Not a problem. Thank you for your time.

IF YES: You will be asked to carefully read each question in the diet questionnaire. As you answer the questions, we will want you to comment on if they are easy to understand and to let us know about words that are not clear. We will also want to know whether you feel the questions are appropriate, and whether you would choose not to answer certain ones. You can write your comments directly on the questionnaire. You will not be required to answer all of the questions on the questionnaire if you do not wish to. It will take approximately 25-35 minutes to go through the questionnaire. The information you give will be kept confidential and your answers will not be used in the study. Do you have any questions or concerns?

Patient: (Answer any questions the patient has to the best of your ability. If needed, the principal investigator can be contacted to answer any questions of uncertainty)

RGM: Are you interested in providing your feedback about this questionnaire

Mr/Mrs. _____?

121

Patient: Yes or No RGM: IF NO: Not a problem. Thank you for your time and consideration.

IF YES: Thank you for your help. Your comments will give us important information and will be very helpful in this research project.

RGM: (Provide patient and/or primary household shopper / caregiver with a copy of the questionnaire, and explain how to comment)

In case the pt asks why we need their help: We need your feedback to help us make a clear and concise questionnaire about the foods that dialysis patients eat at home. We will use all of the feedback to improve the questionnaire and make sure that it is asking the right questions in a way that is understandable by everyone. Then we would like to use it for a study that we are planning to do. The reason we are planning to do this study is because meat, poultry and fish food items are important sources of protein in the hemodialysis diet and may contain added amounts of potassium and/or phosphorus that are not seen on the nutritional label. The results of the questionnaire will help us determine the meat, poultry and fish products that patients consume most often. We will use this information to help us decide which foods to analyze for the phosphorus, potassium and sodium content. There is currently no Canadian information about the amount of phosphorus and potassium in foods that contain additives, so the study that we are planning to do will give us more information to help patients with kidney disease to better manage their renal diet.

122

Appendix C – Recruitment Pre-Amble

Food Questionnaire

123

Study Title: The phosphorus and potassium content of frequently consumed types of meat, poultry and fish items

among patients with end-stage renal disease

Recruitment Pre-Amble

RGM = Research Group Member RGM: I would like to talk to you about an opportunity to take part in a dialysis

nutrition study. The study is about which types of meat, poultry and fish products you consume most often. In order to do this, we will give you a questionnaire to complete, which will include questions about which types of meat, fish and poultry you purchase and how frequently you eat them.

The reason we are doing this study is because meat, poultry and fish food items are important sources of protein for your diet and may contain added amounts of potassium and/or phosphorus that are not seen on the nutritional label. We will use the information you provide us to find out more about the phosphorus, potassium and sodium content of meat, poultry and fish products that you consume most often. There is currently no Canadian information about the amount of phosphorus and potassium contained in foods with additives, so this study will help give us more information to help manage the renal diet. Would you like to hear more about the study?

Patient: Yes or No RGM: IF NO: No problem. Thank you for your time.

IF YES: To participate in the study, you will be asked to fill out a questionnaire which has questions about which types of meat, fish and poultry you purchase and how often you eat them. It will also include questions about how you or the primary caregiver purchase and prepare foods and some general questions about you. The research staff will also collect some information from your chart about your kidney disease. The questionnaire should take approximately 25-35 minutes to complete. You can decide to complete it right away, or to take it home and bring it back at a later visit. You may choose not to answer or skip any questions. However, if you require clarification in order to answer a question, we will be available to assist you.

124

There are no risks anticipated with this study. Also, your participation is completely voluntary. You also have the right to withdraw from this study at any time and your medical care will not be affected. Do you have any questions or concerns?

Patient: (Answer any questions the patient has to the best of your ability. If needed, the principal investigator can be contacted to answer any questions of uncertainty)

RGM: Are you interested in participating in this study Mr/Mrs. _____? Patient: Yes or No RGM: IF NO: No problem. Thank you for your time.

IF YES: Please read the consent form. If you cannot read the consent form, let me know, and I will read it to you. You may take as much time as you like to decide if you wish to participate in the study. Please also let me know if you have any questions about the study. If you decide to participate, you will be asked to sign and date the consent form. You will then be given a copy of the consent form for your reference.

Patient: (May potentially ask questions) (Signs the consent form OR Doesn’t Sign the Consent form) RGM: IF NO: No problem. Thank you for your time.

IF YES: Thank you for deciding to participate. Your participation will give us valuable information and will be very helpful in this research project. (Photocopy the consent form. Give the copy to the participant and store the original in the white binder labeled “Study 1 research consent forms”)

RGM: (Provide patient and/or primary household shopper / caregiver with a copy

of the questionnaire, and explain how to complete the questionnaire. Provide assistance in completed the questionnaire as needed.)

125

Appendix D – Patient Consent Form

Food Questionnaire

126

Consent to Participate in a Research Study

Study Title: The phosphorus and potassium content of frequently consumed types of meat, poultry and fish items among patients with end-stage renal disease

Study Investigators and Study Contact: Principal Investigator:

Arti Sharma Parpia, RD St. Michael’s Hospital 30 Bond Street, 8CC, Rm 014 Toronto, ON M5B 1W8 Tel: (416) 864-6060 ext. 6113 Availability: 9:00 am – 5:00 pm, Monday to Friday

Co-Investigators:

Pauline Darling, RD, PhD 1. Associate Scientist, Li Ka Shing Knowledge Institute St. Michael’s Hospital 2. 209 Victoria Street, 4th Floor, Suite 411 3. Toronto, ON M5B 1W8 4. Tel: (416) 978-5556 Availability: 9:00 am – 5:00 pm, Monday to Friday

Marc Goldstein, MD

Staff Nephrologist, St Michael’s Hospital 30 Bond Street, 8CC, Rm 014 Toronto, ON M5B 1W8 Tel: (416) 864-5290 Availability: 9:00 am – 5:00 pm, Monday to Friday

Mary L’Abbé, PhD

Earle W. McHenry Professor, and Chair, Department of Nutritional Sciences Faculty of Medicine, University of Toronto FitzGerald Building, 150 College Street, Rm 315 Toronto, ON, Canada M5S 3E2 Tel: (416) 978-7235 Availability: 9:00 am – 5:00 pm, Monday to Friday

Other Research Study Members:

Carol Huang, RD Registered Dietitian, Nephrology St. Michael’s Hospital

Kristen Wetherall, HBSc Dietetic Student, Volunteer Services St. Michael’s Hospital

Maxine Seider, BSc, MSc Volunteer Research Assistant St. Michael’s Hospital

Ms Arti Sharma Parpia is a student at the University of Toronto, working on a Masters of Science degree in the Department of Nutritional Sciences. Ms Sharma Parpia’s faculty supervisor is Dr. Pauline Darling.

127

Introduction You are asked to consider participating in our study to find out more about the food you usually eat at home. Before agreeing to take part in this research study, it is important that you read all of the information in this research consent form. If you cannot read, this information will be read to you. This form includes details we think you need to know in order to decide if you wish to take part in the study. All research is voluntary and you do have the option to decline participation in this research study. If you have any questions, ask a study investigator or a research study member. You should not sign this form until you are sure you understand the information. Purpose of the Research Study You are asked to consider participating in this study to find out more about the types of meat, poultry and fish products you usually eat at home. Meat, poultry and fish food items are important sources of protein for your diet and may contain added amounts of potassium and/or phosphorus that are not seen on the nutritional label. We will use the information you provide us to find out more about the phosphorus, potassium, protein and sodium content of the foods most commonly eaten by patients with chronic kidney disease. Description of the Research Study If you choose to participate in this study, you will be asked to complete a questionnaire which will include questions about which types of meat, fish and poultry you usually eat at home and how frequently you eat them. It will also include questions about how you or the food shopper at your home, purchases and prepares the food at your home, and some general questions about your education, ethnicity and annual income. The questionnaire should take approximately 25-35 minutes to complete. You can decide to complete it right away, or to take it home and bring it back at a later visit. We will also collect demographic information (e.g., age, gender) and information about your kidney disease and nutritional status from your medical record. There will be about 100 individuals participating in this study being conducted at St. Michael’s Hospital. Potential Harms There are no harms anticipated with participation in this study. Completing the questionnaire may be a slight inconvenience. If you feel uncomfortable answering any of the questions, you can choose not to answer them. Potential Benefits You may receive no direct benefits from being in this study. However, results from this study will be used to provide further information about the protein, potassium, phosphorus, and sodium content of foods with and without additives, which may help in managing chronic kidney disease. Protecting Your Health Information All information obtained during this study will remain confidential. You will be identified by a study code number and any personal information that includes your name will be securely stored in a locked cabinet, inside a locked room. Only your study code number will be on the data collection forms. The data collection forms will also be securely stored in a locked cabinet in a locked room. Electronic files will be stored securely on the hospital/institutional network. No information identifying you will be allowed off site in any form. The investigators will protect your records and keep all the information in your study file confidential to the greatest extent possible. However, it is important to understand that despite

128

these protections being in place, there is a risk of unintentional release of information. Experience in similar studies indicates that the greatest risk in this study to you is the unintentional release of information from your health records. The chance that this information will accidentally be given to someone else is small. By signing this form, you are authorizing access to your medical records by the study investigators/study team, and the St. Michael’s Hospital Research Ethics Board. Such access will be used only for the purpose of verifying the authenticity and accuracy of the information collected for the study, without violating your confidentiality to the extent permitted by applicable laws and regulations. Federal and Provincial Data Protection regulations, including the Personal Information Protection and Electronic Documents Act (PIPEDA 2000) and the Personal Health Information Protection Act (PHIPA 2004) of Ontario, protect your personal information. They also give you the right to control the use of your personal information (including personal health information) and require your written permission for this personal information to be collected, used, or disclosed for the purposes of this study, as described in this consent form. You have the right to review and copy your personal information collected in this study, and to request corrections to any information inaccurately recorded. Once the study has been completed and published, the link between your name/ identifying information and your study data will be broken. The study data will be kept in a secure location for up to 10 years and then securely destroyed. In no way does signing this form waive your legal rights nor release the investigators or involved institutions from their legal and professional responsibilities. Study Results The study results may be presented as a Masters thesis at the University of Toronto. It is possible that the results of this study may be published in scientific literature or presented at a conference or seminar. Confidentiality will be upheld and no names or identifying information about you will be used in any publication or presentation. If you are interested in obtaining a copy of the study results/publication, please contact Arti Sharma Parpia, Principal Investigator. Participation and Withdrawal Participation in any research study is voluntary. If you choose not to participate, you and your family will continue to have access to customary care at St. Michael’s Hospital. If you decide to participate in this study you can change your mind without giving a reason, and you may withdraw from the study at any time without any effect on the care you and your family will receive at St. Michael’s Hospital.

If you withdraw from the study, your study data/information collected about you up to that time will be used to maintain the integrity of the study, but no more data about you will be collected. Research Ethics Board Contact If you have any questions regarding your rights as a research participant, you may contact Dr. Bob Hyland, Chair of Research Ethics Board, St. Michael’s Hospital, at 416-864-6060 ext. 2557 during business hours. The Research Ethics Board is also required to do periodic review of ongoing research studies. As part of this review, someone may contact you from the Research Ethics Board to discuss your experience in the research study. Study Contact If you have any further questions about this study, please call Arti Sharma Parpia, Principal Investigator at St. Michael’s Hospital, Hemodialysis Unit at (416) 864-6060 ext. 6113.

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Appendix E – Data Collection Form

Food Questionnaire

130

Data Collection Form

(Data from chart)

Participant ID # _______________

Date: _______________

1) Age (years): _________

2) Gender: □ Male □ Female

3) Dialysis Vintage / Dialysis Start Date: ________________

4) Mode of Dialysis: □ Conventional In-centre hemodialysis (4 hours, 3x/week) □ Home Peritoneal Dialysis □ Short Daily In-Centre Dialysis □ Other: ________________________________________

5) Significant Co-Morbidities

□ Diabetes □ Hypertension □ Cardiovascular Disease

6) Dry Weight: ___________

7) Height: ___________

8) BMI: ___________

9) Biochemical Indices of Nutritional Status:

Albumin: __________ PO4: ___________ Calcium :___________ Potassium: __________ Pre-Dialysis Urea ________ PRU: _____________

131

Appendix F

Comparison of Store Brands and National Brands among Major

Subgroups of MPF Foods

132

Comparison of store brands and national brands among major subgroups of MPF foods

Chicken Beef Fish and Seafood Processed Meats

Store Brand

n =12

National

Brand

n = 11

Store Brand

n = 11

National

Brand

n = 1

Store Brand

n = 14

National

Brand

n = 6

Store Brand

n = 7

National

Brand

n = 10

Mean (SD)

(min, max)

Mean (SD)

(min, max)

Mean (SD)

(min, max)

Mean (SD)

(min, max)

Mean (SD)

(min, max)

Mean (SD)

(min, max)

Mean (SD)

(min, max)

Mean (SD)

(min, max)

Sodium

(mg/100g) 282 (149)

(49, 470)

404 (214)

(51, 690)

247 (213)

(60, 540) 440

322 (215)

(42, 700)

251 (209)

(34, 590)

1590 (708)

(950,2800)

1083 (275)

(800,1800)

Potassium

(mg/100g) 449 (191)

(300, 920)

465 (219)

(310,1100)

360 (80)

(250, 480) 300

175 (147)

(22, 420)

233 (164)

(10, 450)

350 (128)

(220, 570)

574 (328)

(230,1100)

Phosphorus

(mg/100g) 218 (30)

(190, 290)

257 (53)

(190, 360)

214 (39)

(150, 270) 170

236 (91)

(130, 510)

213 (51)

(140, 290)

290 (121)

(150, 500)

274 (45)

(200, 370)

Protein

(g/100g) 26 (2)

(23, 29)

26 (3)

(22, 30)

23 (6)

(13, 33) 16

17 (2)

(13, 21)

18 (4)

(12, 23)

26 (13)

(13, 49)

20 (9)

(13, 41)

Phosphorus:Protein

(mg P/g Pro) 8.3 (1.0)

(7.3, 10.2)

10.2 (2.5)

(7.4, 15.8)

9.6 (1.2)

(8.1, 12.1) 10.2

14.1 (5.3)

(9.1, 27.9)

12.0 (3.2)

(9.2, 17.4)

11.9 (4.1)

(8.6, 19.9)

15.1 (4.7)

(9.1, 19.8)

PO4 additives

(n, %) 0 (0) 4 (36) 1 (9) 0 (0) 4 (29) 3 (50) 7 (100) 7 (70)

Seasoned

(n, %) 9 (75) 6 (55) 1 (9) 0 (0) 0 (0) 0 (0) 1 (14) 2 (20)

Price

Mean (SD) 12.06

(5.20)

10.66

(3.83) 8.57 (2.89) 14.99 7.60 (3.74) 7.66 (1.97) 5.21 (1.14) 5.12 (1.06)

Comments: We were unable to ascertain if store brands differed from national brands due to variability in

products. There were no consistent trends observed and it was challenging to further analyze subgroups

due to small sample sizes. In addition, some types of MPF were all store brand (i.e. rotisserie chicken,

ground beef, steak), therefore we were unable to make a comparison.

133

Appendix G

Comparison of Analyzed Nutrient Content Among

Processed and Minimally Processed Foods

134

Comparison of analyzed nutrient content among processed and minimally processed foods

(n=91)

Processed

n=55

Minimally

Processed* n=36

Mann-Whitney

Median (min, max) Median (min, max) p-value

Sodium

(mg/100g) 510 (200, 2800) 62 (34, 460) < 0.001

Potassium

(mg/100g) 320 (<10, 1100) 400 (66, 490) 0.12

Phosphorus

(mg/100g) 230 (130, 500) 235 (100, 510) 0.75

Protein

(g/100g) 21 (12, 49) 24 (13, 33) 0.05

Phosphorus:Protein

(mg P/g Pro) 11.6 (6.9, 19.9) 9.9 (7.2, 27.9) 0.02

abc Medians significantly different by Mann-Whitney and p<0.05 if subscripts differ from each other

†Kruskal-Wallis test

*Includes foods from seafood counter where an ingredient list was not available

Comments: Minimally processed foods were defined as an unprocessed food altered in ways that

do not add or introduce any substance, and usually subtract parts of the food, without

significantly changing its nature and/or use (Moubarac et al, 2014). Since this definition is in line

with our definition for reference foods (as a fresh MPF item that contained no additional

ingredients or additives), we combined reference foods and minimally processed foods for the

purpose of this analysis.

The minimally processed food group included all fresh chicken breast, ground beef, steak,

tilapia, some sole products, plus reference products. The processed foods group tended to be

completed different types of MPF (i.e. bacon, deli ham, frozen chicken breast, chicken strips,

rotisserie chicken, beef burger, shrimp and some sole products). Thus, we did not feel it was

methodologically sound to compare two groups containing completely different types of MPF.

Carrigan et al (2014) have previously chemically analyzed a low-additive minimally processed

4-day menu compared to an additive-rich processed 4-day menu and determined that the

processed diet contained 60% more phosphorus.

135

Appendix H

Comparison of Analyzed Nutrient Content Among

Breaded Chicken Products

136

Comparison of Analyzed Nutrient Content Among Breaded Chicken Products

Comments: Breaded chicken was identified as a major source of phosphate additives (Lampila, 2013),

and occupies a substantial amount of shelf space at the grocery store, therefore we decided to chemically

analyze these products. However, as the frequency of consumption of breaded chicken was not ranked as

high as other types of MPF, we did not include breaded chicken products in the analysis of commonly

consumed MPF. Similar to other types of MPF, breaded chicken with phosphorus additives appear to

have higher phosphorus content, in amounts that are in line with the packaged chicken strips and frozen

chicken breast products that were analyzed.

Protein

(g/100

g)

Phosphorus

(mg/100g)

Potassium

(mg/100g)

Sodium

(mg/100g)

P:Pro

(mg P/1 g

Pro)

PO4

additives

(Y/N)

Compliments

Chicken Strips,

Breaded cutlets

10.91 260 210 570 23.8 N

Maple Leaf Prime

Chicken Strips,

Breaded

18.11 310 300 800 17.1 Y

President’s Choice

Chicken Breast

Fillets, Breaded

15.57 290 470 450 18.6 Y

Irresistibles

Chicken Breast

Fillets, Breaded

15.58 200 280 370 12.8 N

137

Appendix I

The accuracy of Canadian Nutrient File data for reporting

phosphorus, potassium, sodium and protein

in commonly consumed meat, poultry and fish products

138

The accuracy of Canadian Nutrient File data for reporting phosphorus, potassium, sodium

and protein in commonly consumed in meat, poultry and fish products

The Canadian Nutrient File (CNF) is a comprehensive food composition database

containing average values of chemically analyzed nutrients for foods (CNF User’s Guide, 2010).

Clinicians often use the CNF as a point of reference for the purposes of assessing dietary intake,

monitoring population-wide nutrition programs and menu planning (CNF User’s Guide, 2010).

Approximately 59% of data in the CNF is unchanged from the U.S Department of Agriculture

(USDA) nutrient database, while the remaining is periodically modified to reflect differences

specific to the Canadian food supply (CNF User’s Guide, 2010). The purpose of this study was

to examine if nutrient data obtained from chemical analyses of commonly consumed meat,

poultry and fish (MPF) foods was comparable to nutrient data in the CNF.

We administered a modified version of the Diet History Questionnaire II, adapted for

Canada from the National Institute of Health (Csizmadi et al, 2007) to patients (n=67) receiving

hemodialysis and peritoneal dialysis in Toronto, Canada from July to September 2013.

Unbreaded chicken, ground beef, steak, beef burgers, white fish, shrimp, deli ham and bacon

were identified as the most commonly consumed MPF foods. MPF foods (n=91) from twelve

subtypes were purchased from the top 3 grocery store chains in Canada and cooked. Protein,

sodium, phosphorus and potassium content were analyzed using the Association of Analytical

Communities (AOAC) official methods 992.15 and 984.27. Discrepancies were defined as CNF

values that differed by more than two standard deviations from the mean analyzed value.

Comparable foods in the CNF database (2010) were available for 10 of 12 subtypes of

MPF foods (n=71). Based on our definition, 30% of foods had discrepancies in sodium, 60% in

potassium, 50% in phosphorus and 40% in protein between CNF and analyzed foods (See

Table). It should be noted that 60% of the CNF values were based on food analysis conducted

prior to 2000, dating as far back as 1981. All CNF values except for the nutrient content of steak

and the protein content of chicken breast originated from the USDA nutrient database. While the

CNF contains sources of foods from across Canada, our results were limited to foods purchased

in Toronto, Canada.

139

Importantly, a reasonable level of accuracy in CNF values is needed for nutrients such as

potassium and phosphorus, which are not required to be listed on the Nutrition Facts Table

(Health Canada, 2004). Our results demonstrate rather large discrepancies between analyzed and

CNF values. For example, fresh skinless chicken breasts contained on average almost twice the

amount of potassium stated in the CNF (236 vs. 438 mg/100g), which translates into an error of

two servings of a high potassium food instead of one (Sanghavi et al, 2013). This information

impacts those who require a dietary potassium restriction such as those with kidney disease and

others with impaired urinary potassium excretion (IOM, 2005). In addition, the CNF database

lacked comparable foods for newer food items such as, unbreaded chicken strips and frozen

chicken breast, which occupy substantial amounts of shelf space.

In conclusion, we found considerable discrepancy in the sodium, potassium, phosphorus

and protein content listed in the CNF versus the chemically analyzed nutrient content of

commonly consumed MPF foods by patients with CKD. Our results highlight the need for

further studies to verify and extend these analyses to more foods in order to more accurately

reflect the nutrient value of current food supply in Canada. This initiative would enable patients

to be better able to make informed and appropriate food choices that are in compliance with their

dietary requirements.

140

Comparison of the nutrient content of chemically analyzed foods versus data for

comparable foods from the Canadian Nutrient File (CNF)

Food subtypes Data Source Year n Na K P Pro

Unbreaded Chicken

Chicken breast,

Fresh, Skinless

Analyzed 2014/15 8 55 (10) 438 (36) 255 (21) 28 (1)

CNF #892 1996 - 51 236* 217 30

†

Chicken, Rotisserie Analyzed 2015 5 306 (90) 360 (26) 200 (12) 27 (1)

CNF #6648 2009 12 381 245* 248

* 18

*

Lean Ground Beef,

Fresh

Analyzed 2015 6 70 (9) 383 (39) 213 (20) 23 (2)

CNF #2685 1988 - 64 291* 162

* 30

*

Top Sirloin Steak,

Fresh

Analyzed 2015 6 65 (8) 458 (23) 263 (8) 30 (2)

CNF # 6144 2006 6 58 351* 219

* 29

Beef Burger, Frozen Analyzed 2015 7 464 (73) 296 (50) 183 (29) 18 (4)

CNF #2704 1988 2 77

* 305 174 23

White Fish

Tilapia Analyzed 2015 6 58 (37) 390 (51) 205 (14) 20 (2)

CNF # 5967 2006 2 56 380 204 26*

Sole Analyzed 2015 7 301 (113) 158 (70) 280 (108) 17 (2)

CNF #0307 1989 - 105

≠ 344

*≠ 289

≠ 24

*

Shrimp Analyzed 2015 7 510 (127) 58 (50) 199 (62) 15 (3)

CNF #3211 1989 >25 148* 185

* 205 20

Deli Ham Analyzed 2014/15 11 993 (58) 551 (317) 251 (37) 16 (3)

CNF #1149 1981 - 1304

* 287 153

* 17

§

Bacon Analyzed 2014/15 8 1625 (658) 355 (133) 301 (115) 31 (11)

CNF #5406 2003 4 2073 498 480

* 39

Values for analyzed and reference foods are expressed as mean (SD)

Abbreviations: CNF = Canadian Nutrient File; Na = Sodium, K = Potassium, P = Phosphorus, Pro =

Protein

*Indicates that the mean chemically analyzed value differed significantly from the CNF value by more

than two standard deviations

†n = 16 products

≠ n = 11 products

§ n = 2 products