Objectives of the lesson

1. Carbohydrates and gut microbiota

2. Proteins – are they a nutrtional problem?

3. Vitamins in a nutshell

Lesson 2

© Katarína Babinská, MD, PhD. MSc., 2019

katarina.babinska@fmed.uniba.sk

Clinical case

• Patient: Joanna, 36 y old

• Overweight (BMI 28)

• Problems with glycemia

– fasting normal

– abnormally high levels after meal

• Complains of chronic constipation

• Need to modify carbohydrate intake?

Carbohydrates

Primary function: energy source

Types and dietary sources of carbohydrates

1. Monosaccharides (1 carbohydrate unit in molecule)

• glucose, fructose, galactose (fruit, vegetables, honey)Glucose

2. Disaccharides (2 carbohydrate units in molecule)

• saccharose (sugar, sweets, soft drinks)

• lactose (milk, milk products)

3. Polysaccharides (10 and more carbohydrate units)

• starch – main carbohydrate in human diet

(cereals, legumes, potatoes, fruit, vegetables)

- energy value of carbohydrates 17,1 kJ (4,1 kcal)/ 1g

Proteins Fats Carbohydrates

25- 30 %

10- 15 %

55 - 60 %

Recommended intake of

carbohydrates

• 55 – 60 % of daily energy intake

• of that mono and disaccharides:

maximum 10 % of energy

Foods rich in simple carbohydrates (mono/disachcarides)

(candies, soft drinks, crackers, sweet bakery....)

- if consumed in excess

• low nutritional value:

- rich in calories,

- but often poor in vitamins, minerals, etc. („valuable“ nutrients)

• risk of tooth decay

(oral bacteria – carbohydrate fermentation - acid formation –

enamel destruction)

Mono / disaccharides

- fast source of energy

- rapidly digested and absorbed in the gut

- rapid increase of glycaemia

- rapid increase in insulin secretion with adverse metabolic effects:

preferred fuel - glucose,

therefore fat deposition

faster onset of hunger –

blood glucose drops rapidly

down

CVD, DM risk

Polysaccharides

- „easily digested“ – similar metabolic effect as simple carbohydrates (or

slightly lower)

- e.g. white bread !!!

Slowly digested poysaccharides

- slower and prolonged increase in glucose level

- glycaemia does not reach that high levels

- metabolically more

advantageous

- „longer term“ source of

energy - longer feeling of

satiety

- dietary fibre containing

carbohydrates

Glycaemic index (GI)

• Indicates to what extent a food item causes elevation of blood glucose level

• high glycaemic index GI – food significantly increases glycaemia

• foods with lower GI – less increase of glycaemia

Glycemic load

- takes into account both the

amount of carbohydrate in the

food in relation to its impact on

blood sugar levels.

Fructose and health

• often added as a sweetener

• of major concern

• associations with

• icreased fat deposition in the

liver and skeletal muscle

• insulin resistance, obesity,

and the associated risk of

DM 2

• shown in animal studies, not

that much in human studies

• more research needed

Dietary fibre

- several chemical compounds (mostly polysaccharides - macromolecules)

collectively referred to as ditary fibre

a/ water soluble b/ water insoluble

- indigestible component of diet

- it cannot be broken down by digestive juices

- the GI secretions lack enzymes for digestion of fibre

- is not absorbed in the intestines

- fermented by microorganisms (mainly) bacteria living in the GI system

Food sources

- plant foods (cereals, legumes, vegetables, fruits, nuts)

- recommended intake 20 - 30 g/day

- „protective nutrient“ - displays many positive effects

Water soluble fibre - in GIT absorbs water, creates a gel

• reduces glucose absorption – prevents too fast increase in glycaemia

• helps to reduce blood cholesterol (enhances excretion of bile acids via faeces)

Effects of dietary fibre in the human body

Water insoluble fibre

absorbs water in alimentary tract, increases the volume of its content

stimulates intestinal motility

lowers the passage time, thus the exposure of mucosa to harmful substances

aids defaecation – prevents constipation

triggers the feeling of satiety (obesity prevention –see a scheme in the next slide)

Dietary fibre - effective in prevention of cardiovascular diseases, cancer, obesity,

constipation

Dietary fibre and gut microbiota dietary fibre - „food for the microbes“ living in GIT

Intestinal microbiota

more microbial cells than cells of the human body, 1-2 kg

mostly anaerobes, main representatives: Bacteroidetes, Firmicutes

Functions

ferment the dietary fibre - formation of short chain fatty acids – utilized as energy

for intestinal mucosal cells

growth of fermenting bacteria – lower pH

and suppress growth putrid or pathogenic

bacteria

quantity of bacteria - the content of

large intestine – enhanced motility

The gut – brain axis

synthesis of bioactive compounds -

effects on

the intestinal epithelium

local mucosal immune system

the enteric nervous system

- transmission of signals

from the gut to the brain

= gut-brain axis

Dysbiosis

- abnormal composition of gut microbiota

- associated with acute diarrhoea

- linked to chronic diseases (obesity, diabetes

mellitus, Crohn´s disease, etc.)

- increasing evidence shows that it may play role

in pathomechanisms of some CNS disorders

(depression, schizophrenia, autism, etc.).

- microbial colonization occurs after birth

- birth „per vias naturales“ - crucial

- Cesarean section – different microbiota in early

age – may adversely impact development of

the nerveous system, immune system

Gu

t-bra

in a

xis

Clinical case

• Patient Anna – she´s vegan

• She came to doctor´office for an advice:

„What to eat, in order to have adequate protein

intake?“

Recommendation:

• Eat a variety of foods

• Combine various plant foods rich in protein:

- legumes - soy products

- cereals - nuts

• Why?

Proteins

Function

• synthesis of tissues (body proteins)

• synthesis of enzymes, hormones, antibodies, plasma proteins....

• source of energy (under some circumstances)

Proteins

Structure

• macromolecules composed of amino - acids (AA)

• human body - built from 20 different amino acids

Amino acids

1. essential

– cannot be synthesized in the human body,

– provided only by food

• adults - 8 essential AA • child - 10 essential AA

2. non - essential – can be synthesized in the body from essential AA

Plant sources

- soy, legumes, bread, cereals, potatoes

- incomplete protein (= protein with lower biological value) = less adequate AA composition

usually poor in some essential amino acids

synthesis of body proteins is inefficient if any of the essential AA is missing !

Animal sources

- meat, fish, eggs, milk, milk products, cheese

- complete protein (protein with higher biological value)

= adequate AA composition

contains all essential AA in adequate amount

more efficient utilization of AA in synthesis of body proteins

Main food sources of protein

Energy value of protein

17,1 kJ/ 1 g

Protein requirements

• some body protein is degraded daily (obligatory loss) – needs to be replaced

• recommended protein intake: 10-15 % of daily energy intake

• higher protein requirements (tissue synthesis)

- children and adolescents,

- pregnant and lactating females

- sportsmen

- patients (mainly chronic diseases)

Proteins Fats Carbohydrates

10-15 %

Proteins - summary

protein rich food may be rich in saturated fats

It is recommended to prefer low fat alternatives

- full milk yoghurt / low fat yoghurt

- fatty meat / lean meat, etc.

people consuming exclusively plant food shouldcare about the variety of their diet

by consumption of a variety of different plant foods adequate amount of AA can be supplied(e.g. in vegetarian diet)

I´m a vegetarian. Is my

protein intake

adequate?

the intake of protein in economically developed countries is generally adequate

or slightly higher protein than recommended

exception may be some high risk groups (vegetarians, elderly, low income)

Vitamins

• involve 13 substances

– fat soluble vitamins (A, D, E, K)

– water soluble vitamins (vitamin C and the B complex: B1, B2, B6, B12,

niacin, folate, biotin, pantothenic acid)

Function

• components of enzyme systems (co-factors)

• involved in the regulation of metabolism

• Individual vitamins often associated with a

specific function

– Vit A – vision

– Vit K – blood clotting

– Vit B12 – erythropoiesis

– Vitamin E – antioxidant

– Vitamin D – bone formation, etc.

Sources of vitamins

• nutrition

– should be the only/main source of vitamins

(except vitamin D – sun exposure)

• Some vitamins can be produced in the human body

vitamin K, B12– in small and insufficient amount

– produced by bacteria in large intestine – minimum absorption

vitamin D - sufficient amount produced in exposure to sunlight

vitamin A - produced in the body if sufficient amount of provitamine

available (b-carotene)

Vitamin pills

- contain „only“ vitamins

- do not fully replace healthy diet

- diet contains also other bioactive substances with biologically – strenghten the

effects of vitamins

- suitable in some circumstances – disease, diet, the elderly, pregnant women...

Do I need vitamin pills?

Risks of insufficient vitamin intake

Avitaminosis

- absolute deficiency – at present time rare in developed countries

- results in disorders with typical symptoms – currently very rare

vit. A – night blindness, blindness

vit. D – rhachitis

Hypovitaminosis

- intake of many vitamins, mainly B and C is lower than the recommendations

- large part of population are vitamin D deficient

- typical are mild forms of deficiencies – rather common

- no clinical symptoms present, can be diagnosed by examination of blood levels

- causes metabolic abnormalities and increased risk of non-communicable

diseases (cardio-vascular, osteoporosis, etc.)

Risks of excessive vitamin intakes

- Hypervitaminosis – acute or chronic toxicity

Simple recommendation to supply

sufficient amount of vitamins:

...eat a variety of foods...

Questions to study

• Carbohydrate types and glycemia

• Health risks associated with overconsumption of mono and

disaccharides

• Fructose and health

• Dietary fibre, health effects, recommended intake, food sources

• Gut microbiota, main representatives, health effects

• Gut brain axis – what is, communication pathways, health effects

• Proteins – dietary sources

• Complete, incomplete protein – what determines the quality?

• Vitamins: hypovitaminosis – current problem and its consequences

• Vitamin pills – what is their disadvantage in comparison to natural

vitamin sources