A Supplement to Food Product Design

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Formulating Glycemic Strategies

Formulating Glycemic Strategies

The chemical nature of carbohy-drates is not a reliable indicator oftheir physiological effect.

In an effort to clarify the physiologicalimpact of carbohydrates, the glycemicindex (GI) concept was developed and published in 1981 as “GlycemicIndex of Foods: a Physiological Basis forCarbohydrate Exchange” in the AmericanJournal of Clinical Nutrition. The GI is ameans of classifying carbohydrate-con-taining foods based on their potential toincrease blood glucose. The initial objec-tive was to provide improved advice to

people with diabetes regarding their car-bohydrate intake. During the last 20 years,research has been undertaken to evaluatethe usefulness of GI. The glucoseresponse to foods inherently varies fromperson to person and according to the con-text in which the food is consumed.Reproducible and consistent GI measure-ments are possible when undertaken inaccordance with established methodolo-gy. The debate continues as to the useful-ness and consistency of GI.

Professor Jennie Brand-Miller andcolleagues at the University of Sydney,

Australia, have developed a center forthe measurement of GI, and tables havebeen published ranking over 1,200 foodsby GI, including pure carbohydrates andcommercial products. Although use ofGI remains controversial, its acceptanceis increasing, especially in Europe andAustralia. In the United States, GI hasgained less acceptance. For example,one of the criticisms of GI is that itmeasures the impact of individual foodsand does not necessarily consider theamount eaten or foods in the context ofan overall diet.

Glycemic Response

By Beth Hubrich, R.D., and Lyn O’Brien NaborsContributing Editors

GI measures effects of carbohydrateswith respect to their ability to raiseblood glucose and compares this valuewith blood glucose response to eitherwhite bread or glucose itself. Glycemicload (GL), introduced in 1997, mea-sures the blood glucose response to aspecific weight of a given food. GL,therefore, provides a measure of totalglycemic response to a food or meal. Itis calculated by multiplying the amountof carbohydrate contained in a servingsize (weight in grams or volume in mil-liliters) by the GI value of that fooddivided by 100.

Simply stated, the glycemic responseto a food is a measure of the impact of afood on blood sugar. Foods with rapidlyhydrolyzed and absorbed carbohydratesgenerally have a fast and high impact onblood sugar, resulting in the highestglycemic indexes. Slowly or incom-pletely digested carbohydrates have lowglycemic indexes. In these cases, glu-cose is released gradually into theblood, and the blood sugar response isslow and steady.

In recent years, numerous productsbearing terms such as “net carbs,”“impact carbs,” “low GI,” etc., on packaging have appeared on grocery

shelves. This information appears out-side the Nutrition Facts Panel, as theseterms are not approved by FDA. Foodmanufacturers also place on the productpackage a statement indicating that onlythe “net carbs” or “impact carbs” affectblood glucose. Such products haveincreased consumer awareness ofglycemic response.

Clinical significance of GIHealth problems related to being

overweight are becoming the majorhealth concern of the industrializedworld. The World Health Organizationand Food and Agriculture Organizationof the United Nations (WHO/FAO)have stated that, globally, overweight isa bigger problem than undernourish-ment. In “Carbohydrates in HumanNutrition,” they recommended that peo-ple in industrialized countries base theirdiets on low-GI foods to prevent mostcommon diseases of affluence.

High-glycemic foods may stimulatea high insulin demand that, in turn, canlead to postprandial hypoglycemia,which may be implicated in triggeringhunger. Lower-glycemic foods usuallyprovoke less insulin demand and lesspossibility of hypoglycemia. Hence,

lower-glycemic foods may help con-sumers to eat fewer calories. It is impor-tant to note, however, that the relation-ship between GI and insulin demand isnot always linear, and various compo-nents of the food can modify insulinresponse relative to glycemic response.Also, the glycemic response of individ-ual foods and ingredients is influencedby the presence of other foods, process-ing conditions, etc.

The clinical significance of GIremains the subject of intense debate.However, it is clear that the rate and theamount of carbohydrate absorption aftera meal have significant effects on post-prandial hormonal and metabolicresponses. The habitual consumption ofhigh-GI foods may increase risk factorsassociated with obesity, type 2 diabetesand heart disease. Conversely, the con-sumption of foods that elicit low-glycemic responses may help to reducesuch risk factors. GL, as defined above,may be a better predictor of likelyhealth outcomes than GI, per se.

In July 2002, the American Journalof Clinical Nutrition published a specialsupplement that reviewed the history ofGI, the current status of knowledge andrecommendations for future studies.

Calculating the precise glycemic responseof a given food can prove difficult, partic-ularly with unprocessed agricultural ingre-dients like fresh fruit, which can havevarying GIs, depending on the degree ofripeness and other variables.

This review featured an overview ofGI’s implications in health and disease,including discussions relative to type 2diabetes, obesity and heart disease. Inconclusion, a critique argued that insuf-ficient data exists on which to basedietary advice for the achievement ofdisease-risk reduction.

From this review, it is apparent thatgreat effort has been applied to under-standing the role of dietary carbohy-drates in human health and disease risk.While there is no definitive proof thatreducing glycemic impact will preventdisease on an individual basis, epidemi-ological data, together with prospectiveand intervention studies, suggest thatreducing the glycemic effect of the dietmay reduce disease risk. There are nocontraindications, other than that con-sumers may have difficulty in under-standing what action they need to takein order to reduce glycemic challenge.

Recent meta-analysesDuring the last year, several meta-

analyses have been published linkingglycemic response to biomarkers of dis-ease risk. One reviewed 14 randomizedcontrolled studies, which considered therole of low-glycemic diets in the man-agement of diabetes. The studies

involved a total of 356 subjects and last-ed from 12 days to 12 months. The low-GI diets reduced glycated hemoglobin(HbA1C) by 0.43 percentage pointscompared to high-GI diets. HbA1C is awell recognized biomarker of glucosetolerance. The authors’ overall conclu-sion is that low-GI foods have a smallbut clinically useful effect, equivalent topharmacological agents.

Another meta-analysis reviewedinternational nutrition recommenda-tions with special emphasis on carbohy-drate and fiber. The authors also con-cluded that there is a role for reducingthe glycemic response of the diet andrecommended that GI informationshould be incorporated into exchangesand teaching material for individualswith diabetes.

In a review of 16 randomized con-trolled trials published between 1981and 2003, researchers found that low-GIdiets significantly reduced fructosamineby 0.1 mmole per liter, HbA1C by

0.27%, total cholesterol by 0.33 mmoleper liter, and tended to reduce LDL cho-lesterol in people with type 2 diabetesby 0.15 mmole per liter compared withhigh-GI diets. No changes were seen inHDL cholesterol and triacylglycerols.Their findings support the use of GI as ascientifically based tool to enable selec-tion of carbohydrate-containing foodsto reduce total cholesterol and improvemetabolic control of people with dia-betes. There was only limited data onhealthy individuals.

One review of the evidence for low-GI diets in relation to coronary heartdisease identified 15 studies meetingstrict inclusion criteria. There was some(limited) evidence showing a relation-ship between low-GI diets and lowertotal cholesterol (compared to high-GIdiets). A small reduction in HbA1C wasseen after 12 weeks, but not after fiveweeks. The researchers concluded thatmore studies of at least 12 weeks dura-tion are needed.

Whole grains, which have a lower GI thanrefined grains—among other health bene-

fits—recently helped boost sales of bakedgoods like bread, and would make good

additions to foods formulated for reducedglycemic response.

GI and satietyA growing number of studies sug-

gest that reducing the glycemic impactof the diet may help consumers eatfewer calories, although not all investi-gators and reviewers reach the sameconclusion. Studies undertaken includeshort-term assessments using visualscales and ad libitum food intake,and long-term studies focusing onweight loss.

Two recent papers addressed thequestion of whether obese patientsshould be counseled to follow a low-GIdiet. In one favorable review, theauthors noted that the reduction in fatintake widely advocated in the preven-tion and treatment of obesity has thepotential to encourage compensatoryincreases in the consumption of high-GIcarbohydrates. Short-term feeding stud-ies generally show an inverse associa-tion between GI and satiety. Medium-term clinical trials show less weight losson high-GI/GL diets compared to low-GI/GL diets. Epidemiological analyseslink GI to multiple cardiovascular dis-ease (CVD) risk factors and develop-ment of CVD and type 2 diabetes.Physiologically oriented studies inhumans and animal models providesupport for a role of GI in disease pre-vention (risk reduction) and treatment.

Another author concluded that obesepatients should not be counseled to fol-

low a low-GI diet, noting that low GI isrecommended in the management ofdiabetes. A systematic review wasundertaken of intervention studies com-paring high- and low-GI foods and dietson appetite, food intake, energy expen-diture and body weight. Of 31 short-term studies, low GI was associatedwith greater satiety, or reduced hunger,in 15; no difference was seen in 16 (ofwhich two showed greater satiety withhigh GI). Low-GI foods reduced ad libi-tum food intake in seven studies, but notin eight. In 20 longer-term studies,weight loss occurred in four low-GI andtwo high-GI trials, but it should benoted that many of the diets wereisocaloric.

It must be acknowledged that theimpact of food intake on weight man-agement is not an exact science, and it isnecessary to review the totality of avail-able data before reaching conclusions.At this time, the main body of informa-tion linking glycemic response toweight control does seem to favor a dietreduced in glycemic response, com-pared to our current norm.

The European perspectiveThere is growing awareness in

Europe of the concept of GI amonghealthcare professionals and con-sumers. The objective is to improveunderstanding of glycemic control.Media citations have become frequent, particularly in the UnitedKingdom, Germany and Scandinavia.The following extract from “SlimmerStart to the Day,” which appeared inthe Nov. 4, 2003 Daily Mail, is typical:

“Experts at Oxford Brookes Uni-versity calculated the glycemic index (GI) of foods by comparingthe rise in blood glucose after eating different types. They studiedchildren aged 9 to 12 and found those who had a low-GI breakfast ate more moderately for the rest of the day. But those given high-GIbreakfasts were more likely to behungry by lunchtime.”

In the United Kingdom, majorretailers have launched intensive cam-paigns to raise public awareness of thevalue of reducing glycemic response.Products are routinely labeled “low

As American consumers begin to betterunderstand glycemic response, product

developers will have an opportunity toreformulate foods to reduce their glycemicimpact—for example, replacing sucrose or

corn syrup with certain polyols.

GI,” “medium GI” or “high GI” basedon Brand-Miller’s definitions.

To date, there is no harmonized legis-lation in Europe relating to nutrition andhealth claims on food products. However,the European Commission (EC) proposalfor a Regulation on Nutrition and HealthClaims, COM (22) 424 Final, has beenadopted by the EC and is currently underconsideration by the EuropeanParliament and Council of Ministers.This proposal does not currently includemention of GI as a specific nutritionclaim, although comparative claims arepermitted, provided that a 30% change isseen from typical products in a given cat-egory. There is a provision for includingnew claims at a later date.

The National Food Administration ofSweden has endorsed labeling foodswith the claim, “for a healthy blood glu-cose control,” based on their potential toslow glucose uptake.

Recently, BBC News ran a featureon GI with the headline “Diet CrazeGood for the Heart.”

The U.S. perspectiveHealth professionals in the United

States overall have not accepted theconcept of GI reduction. Reasons citedinclude lack of definitive proof; the dan-gers of people with diabetes changingfrom traditional carbohydrate exchangeroutines; and questions as to how dieti-tians might recommend the concept totheir clients.

The debate continues, and there aresome signs of growing acceptance ofGI. For example, the Food and NutritionBoard of the Institute of Medicine of theU.S. National Academy of Sciencesrecently concluded: “There is a signifi-cant body of data suggesting that moreslowly absorbed starchy foods whichare less processed, or have been

processed in traditional ways, may havehealth advantages over those which arerapidly digested and absorbed. Thesefoods have been classified as having alow GI and reduce the glycemic load ofthe diet. Not all studies of low GI or lowglycemic load diets have resulted inbeneficial effects, however, none haveshown negative effects. There are alsotheoretical reasons at a time when pop-ulations are increasingly obese, inactiveand prone to insulin resistance thatdietary interventions that reduce insulindemand may have advantages. In thissection of the population, it is likely thatmore slowly absorbed carbohydratefoods and low glycemic load diets willhave the greatest advantage. ... However,the principle of slowing carbohydrateabsorption, which may underpin thepositive findings made in relation to GI,is a potentially important principle withrespect to the beneficial health effects ofcarbohydrates. Further research in thisarea is needed.”

The American Diabetes Association(ADA) published a statement in Sept.2004, concluding that: “At this time,there is insufficient information todetermine whether there is a relation-ship between glycemic index or

Specifically designing individual productsas well as complete heat-and-eat entréesto keep total glycemic load at suitablelevels might prove a viable route for aid-ing diabetes management in the UnitedStates.

glycemic load of diets and the develop-ment of diabetes. Prospective random-ized trials will be necessary to confirmthe relationship between the type ofcarbohydrate and the development ofdiabetes. The relative importance ofthe glycemic index or load of the dietto the development of obesity will alsoneed to be considered, as excess bodyfat is the single most important deter-minant of type 2 diabetes.”

In Jan. 2005, the ADA published aposition statement on “Standards ofMedical Care in Diabetes.” Among itsrecommendations for medical nutritioncare for people with diabetes, ADAstates: “Both the amount (grams) of car-

bohydrate as well as the type of carbo-hydrate in a food influence blood glu-cose levels. Monitoring total grams ofcarbohydrate, whether by use ofexchanges or carbohydrate counting,remains a key strategy in achievingglycemic control. The use of theglycemic index/glycemic load can pro-vide an additional benefit over thatobserved when total carbohydrate isconsidered alone.”

The Joslin Diabetes Center andJoslin Clinic have developed “ClinicalNutrition Guideline for Overweight andObese Individuals with Type 2Diabetes, Prediabetes or at High Riskfor Developing Type 2 Diabetes.” These

guidelines state: “Reduction of the qual-ity (glycemic index, GI) and quantity(glycemic load, GL) of carbohydratechoices is essential for blood glucosecontrol. The GI/GL concept is animportant factor that patients shouldapply in their daily selection of carbo-hydrates foods.”

USDA, which is responsible formeat and poultry products, has statedthat it will not object to the use of state-ments that do not expressly state orimply a specific level of carbohydratein a product (e.g., “Carb Conscious”and “Carb Wise”), nor will it object toterms such as “Net Carbs,” “EffectiveCarbs” and “Net Impact Carbs” when

While today’s science makes it fairlystraightforward to measure GI on singlefoods, it becomes more complicatedwhen mixtures of ingredients, variousprocessing techniques and personal eat-ing habits are added in.

Bulk Sweetener Sweetness vs. sucrose Kcal/gram Glycemic response vs. glucose at 100Glucose 0.7 4 100Sucrose 1 4 65Fructose 1.4-1.8 4 19Tagatose 1 1.5 3Erythritol 0.6-0.7 0.2 0Isomalt 0.5-0.6 2.0 2Lactitol 0.3-0.4 2.0 3Maltitol 0.8-0.9 2.1 34Mannitol 0.5 1.6 <5Sorbitol 0.6 2.6 <5Xylitol 1 2.4 8Polydextrose 0 1 <7Inulin 0 1.5 4Resistant maltodextrin 0.1 4* 5Resistant starch Low 2 0+**

* Resistant maltodextrin is reduced in calories, but 4.9 kcal per gram is used for regulatory purposes in the United States. InJapan, the caloric value is 0.5 kcal per gram.

** The GI of resistant-starch ingredients depends on the actual resistant starch content.

Table 1: Relative Sweetness, Caloric Availability and Glycemic Response of Selected BulkSweeteners Compared to Glucose, Sucrose and Fructose

used in a truthful and not misleadingmanner. The document can be found at:www.fsis.usda.gov/oppde/larc/ policies/carblabel.htm.

Several petitions relating to carbo-hydrate labeling are pending beforeFDA. In April 2005, FDA announced itwould be conducting an experimentalstudy of carbohydrate content claimson food labels. The purpose of thestudy is to help enhance FDA’s under-standing of consumer response to car-bohydrate content claims on food labelsand to assist the agency in respondingto the pending petitions on carbohy-drate labeling (Federal Register, 2005;70(67):18,032-18,034). FDA has notyet proposed any labeling related to thecarbohydrate content of food.

GI acceptance elsewhereAustralia is leading the way with a

GI logo for use on products accreditedby the University of Sydney (seewww.glycemicindex.com). In order foraccreditation, a product must complywith nutrient profiles specified by theUniversity. South Africa has also wide-ly adopted GI labeling, and the GIFoundation has developed an interestinglogo program encompassing both GIand fat content (see www.gifoundation.com). In Japan, there is growingawareness among healthcare profes-sionals and food manufacturers, andglucose attenuating properties of fiber-based products are being promoted toconsumers.

The Role of specialty carbohydratesSugar alcohols (polyols) such as lac-

titol, xylitol, isomalt, erythritol andmaltitol have a low glycemic effect, as

Fruits that are high in fructose ratherthan glucose have a low to moderateglycemic index and might prove useful informulating products that fit into low-glycemic diets.

Terminology and methodologyThere are a number of definitions relevant to the glycemicproperties of foods. These include:

Glycemic index (GI): The incremental area under the blood glucose

response curve (AUC) of a 50 gram (or 25 gram) available carbohydrate

portion of a test food expressed as a percent of the response to the same

amount of carbohydrate from a standard food (normally glucose) taken by

the same subject.

Glycemic load (GL): GI multiplied by the carbohydrate content of a

typical serving of the food.

Available carbohydrate: Carbohydrate absorbed into the blood from the

small intestine and metabolized.

Carbohydrate by difference: In the United States, carbohydrate is

calculated as the total weight of food less protein, fat, moisture and ash. In

Europe, fiber is considered separate from carbohydrates.

Glycemic glucose equivalents: The weight of glucose in grams that

would be equivalent to a given amount of food in its glycemic effect.

Glycemic effect, glycemic response, glycemic impact, glycemicchallenge: These terms are not formally defined, but generally refer to the

changes that happen to blood glucose after consumption of a

carbohydrate-containing food.

do fructose, polydextrose, resistantstarches and dietary fiber. These ingre-dients are used extensively to complete-ly or partially replace sucrose, glucoseand high-GI polysaccharides such asstarch and maltodextrin in a wide rangeof processed foods, including dairyproducts, baked goods and confec-tionery. The glycemic responses andother properties of a range of carbohy-drates are summarized in Table 1. Itshould be noted that these carbohy-drates may alter glycemic response butnot glycemic index, according to thestrict definition.

Carbohydrates differ physiologicallyin that some are hydrolyzed andabsorbed from the small intestine andare then metabolized in the body tissues(e.g., glucose, fructose, sucrose, cookedstarch); some are incompletelyhydrolyzed and/or absorbed and metab-olized (e.g., lactose, isomalt, sorbitol,xylitol); some are absorbed, not metab-olized and excreted via the urine (e.g.,erythritol, mannitol); some pass throughthe small intestine unchanged and arefermented completely or partially bygut bacteria (e.g., polydextrose, pectin,fructo-oligosaccharides, inulin, resistantmaltodextrin, resistant starch); andsome pass through the digestive tractunchanged and are barely fermented(e.g., cellulose).

Definitive studies specificallyaddressing the role of low-glycemiccarbohydrates in disease risk reductionare few. A recent review of the healthpotential of polyols as sugar replacersplaces emphasis on low-glycemic prop-erties. The same author also presented ameta-analysis of relevant studies,focusing on the impact of GI (or,strictly speaking, glycemic response)on glycated proteins, particularlyHbA1C, at the 2005 Leatherhead FoodInternational Forum, Surrey, England.Based on data linking HbA1C to car-diovascular disease incidence, he con-cluded that a reduction in glycemic car-bohydrate equivalent to 30 grams ofglucose per day could correlate with a

30% reduction in cardiovascular dis-ease risk. This reduction should beachievable by most consumers, andspecialty carbohydrates could assist.

Challenges and opportunitiesIn time, the scientific community

may conclude that overall insulindemand is a key determinant of diseaserisk. This, in turn, largely correlateswith the glycemic impact of the diet.There are exceptions, but overallglycemic impact remains a usefulmarker of physiological challenge.Traditionally, GI has been used to com-pare only “available” carbohydrateswhere “available” means “absorbedinto the bloodstream in the upper gas-trointestinal tract and metabolized.”Glucose, white bread and rice havetypically been used as standards, withcurrent preference for glucose as it iseasier to define. Currently, GI is theparameter that is increasingly beingrecorded on food labels and promotedto consumers. If the traditional defini-tion of GI prevails, consumers wouldnot gain a full impression of how toreduce the glycemic impact of theirdiet. Some foods, such as carrots, havea high GI but low glycemic load.

Certainly it is not realistic for con-sumers to understand the many differ-ent terms associated with the glycemicproperties of foods. Given that onlyone term is likely to reach the public’sperception, it is important that thisterm is defined in such a way that it has the most relevance for consumerhealth. One researcher who intro-duced the term “Glycemic GlucoseEquivalents” recently discussed thispoint and argued for the extension ofthe GI concept to foods. This may be away forward that could benefit con-sumers. Indeed, the concept has recent-ly been adopted by Atkins Nutritionalsas the “Net Atkins Count,” and otherrecent reviews also exist.

Several popular books are raisingconsumer awareness of GI as a strat-egy for improved nutrition. Of these,

“The Glucose Revolution” by Brand-Miller et al. is currently in its 3rd edi-tion. Rick Gallup recently published“The GI Diet,” which makes a usefulattempt at communicating the GIconcept to consumers. However, GIshould not be seen as a diet, butrather a strategy for improved nutri-tion that becomes a lifestyle choice.Consumers will only derive maxi-mum benefit from GI if food labelscan be devised that accurately conveythe relevant information. In turn, leg-islators and regulators will only mod-ify labeling if scientific substantia-tion has been achieved. All thoseinvolved acknowledge the need foradditional studies to fully elucidatethe impact of glycemic reduction ondisease risk in healthy populations.The next step should be to undertakedefinitive studies to improve ourknowledge in this area.

While definitive proof of the role ofGI may be some way off, there is a casethat, in the meantime, consumers shouldbe given the necessary information andfood choices to enable them to reducethe glycemic impact of their diet if theychoose to do so. There is little downsideto this approach.

With a reduction in the glycemicimpact of the diet, a reversal in the trendtoward lifestyle-related diseases may beobserved. It has been estimated that theglycemic challenge of our diet today istypically 10 times as high as it was pre-industrial revolution, and it is easy toimagine that our bodies have found itdifficult to adapt. ■

Beth Hubrich, R.D., is executive directorof the Calorie Control Council and servesas director of health and nutrition commu-nications for CaloriesCount.com, theCouncil’s online dieting toolkit. LynO’Brien Nabors is president of the CalorieControl Council and has been with theCouncil for over 25 years. To view the bibliography for this article, go to www.foodproductdesign.com.

Reprinted with permission from Food Product Design, July 2006©2006 Virgo Publishing. All Rights Reserved.