High Variability In Glycemic Index Values Leads To Low .

JULY 2021EVIDENCE-BASED KETO DIETHigh Variability inGlycemic IndexValues Leads to LowClinical andPractical UtilityKAREN PENDERGRASSIDPendergrass,K. (2021) High Variability inGlycemic Index Values Leads to Low Clinicaland Practical UtilityEvidence Based KetoDiet Research. Spearhead Certifications.1Department of Standards, SpearheadCertifications, Encinitas, CACORRESPONDENCE1 karen@paleofoundation.comKEYWORDSGlycemic IndexGlycemic LoadDiabetes

High Variability in Glycemic Index Values Leads to Low Clinical and Practical UtilityJuly, 2021KETOgenic DIET RESEARCHHigh Variability in Glycemic Index Values Leads to Low Clinical and Practical UtilityKaren E. E. Pendergrass 11Department of Standards, PaleoFoundation, Encinitas, CACorrespondenceKaren E. E. PendergrassDepartment of Standards, PaleoFoundation, Encinitas, CAIDAbstractThe FAO/WHO Report on Carbohydrates in Human Nutrition suggests thatthe concept of Glycemic Index (GI) provides a useful means of selecting themost appropriate carbohydrate containing foods for the maintenance ofhealth and the treatment of several disease states. However, since itspublication,Contact1Email: karen@paleofoundation.com1witter: @5WordsorlessKPthe increasing limitations of the GI and GL concepts havebecome far more apparent, as more recent findings suggest that GI values arean unreliable indicator even under highly standardized conditions, and arethus unlikely to be useful in guiding food choices.KEYWORDSGlycemic Index, Glycemic Load, Diabetes1 INTRODUCTIONThe glycemic index (GI) is a measure of howet al. proposed this method to classify food by howquickly foods raise blood sugar levels.they affect your postprandial glucose levels, or howControversially, the utility of GI values inmuch certain carbohydrates increase in yourchronic disease management remains debatable.bloodstream after eating them. The GI measures anAlthough absolute determinations are known to varyincremental area under the curve and then expresses itamong individuals with diabetes, there has been littleas a percentage [2].data on accuracy and variable sources between healthyadults-therefore making reliable conclusions difficult toGlycemic load (GL) is a concept that was originallyproduce. However, new studies suggest significantdeveloped as a food selection guide for diabeticindividual and intra-individual variances in howindividuals to improve their glycemic control byindividuals respond to a single food challengeclassifying foods into low, medium, and high GIsuggests that GI value determinations may not be thecategories. However, the use of GI has gone beyondcorrect approach for guiding food choices [1].this original intent and it's now being endorsed for useas a labeling tool in order to help reduce chronic2 GLYCEMIC INDEX AND GLYCEMIC LOADdisease risk or serve as a basis behind many populardiets such as South Beach Diet or Ketogenic Diet.The glycemic index (GI) is a tool for rating the effect ofWhile there is some data to support some benefit ofcarbohydrate-containing foods on blood sugar. Jenkinsadhering to a low Glycemic Index and low Glycemic 2021 The Paleo Foundation1

High Variability in Glycemic Index Values Leads to Low Clinical and Practical UtilityJuly, 2021Load diet in the management of diabetes, data isbe considered acceptable limits by biomedicalmixed in its utility for a nondiabetic population [3].researchers ( 5%) [1].Plans to develop a universal measure for food GI, GLOf the variables accounted for, only 5-11% of thewas abandoned in 2008 due of inconsistencies withvariability could be accounted for by age, BMI, TC:HDLprevious research [4]Statistical analyses shows ancholesterol ratio, serum triglyceride, and CRPinconsistent relationship between dietary carbohydrateconcentration. Data suggests that insulin index andcontent or glycemic index values and insulin sensitivityHba1c could account only for 15 and 16% of the inter-[4]. In addition, data from randomized clinical trialsindividual variability, indicating that glycemic status canindicate inconsistent relations between these twoalter the GI status even in healthy individuals [1]. Thisvariables and cardiovascular disease [5, 6] weight losshigh variability suggests an even higher risk of[7, 8] and cancer [9, 10].misclassifying food types and an even more significantlimitation to clinical application as an accurate or3 HIGH VARIABILITY OF GI VALUES TRANSLATESTO LOW CLINICAL UTILITYuniversal measure for foods. While studies haveidentified several methodologic factors that couldaccount for GI values' variability, efforts to addressthese concerns have not yet been successful [15-17, 1].The GI value is considered to represent the inherentIn light of these concerns, this has led to theproperty of the food and not the metabolic response ofrecommendation that GI values be determined inan individual to the food. As such, theoretically, GInormoglycemic individuals. Unfortunately, datavalues should be wholly reproducible within andsuggests that glycemic status still posed a significantamong individuals. However, a review of the publishedissue in the context of GI value variability, even amongGI tables, which is a compilation of the GI values ofnormoglycemic individuals [1].individual foods generated by several laboratories [11,12] indicates remarkably different estimates for the GIEffectively, data indicates that substantial variabilityvalue within a category and even for the same foodexists in the GI values of white bread, despite[13, 14, 15] This could result in a food being ranked asstandardized methodology and multiple testing. Thelow GI by one laboratory and high by another [16],high degree of variability in the GI values underscoresfurther elucidating the issue of using GI for a specificsignificant potential to misclassify foods into one orfood as a universal measurement.more categories based on their GI values (low,medium, and high). The implications of these findingsWhile GI was one of the most important concepts inon Glycemic Index estimates and their associationsnutrition science, many studies have shown that itwith chronic disease risk warrant major reconsiderationmight not be reliable because there can often be afor their clinical utility.large variation across people's responses even whenfollowing recommended methodology for testing. Onestudy found an intra-individual CV (20% deviation) andan inter-individual CV (25% deviation). While4 MIXED MEALS AND FURTHER GIINACCURACIESaddressing methodologic variables did improve theseCVs slightly, they still didn't reach what would typically 2021 The Paleo FoundationRanking meals by GI has been performed by adding2

High Variability in Glycemic Index Values Leads to Low Clinical and Practical UtilityJuly, 2021the GI values of food components, but whether thelimitations of the GI and GL concepts have become farsums of GIs can reliably calculate a meal's value ismore apparent, and the severity of the limitationscontroversial. In one study, researchers used GI valuesassociated with GI and GL values underscores the needtaken from the International Table of GIs to predict thefor further research on the concept to obtain moreGI of 13 simple breakfast meals. However, when theyaccurate estimated values for foods and meals. Further,tested these predictions against measured results, noother factors must be considered when establishingassociation was found between calculated and actualassociations between diets or foods based on GI andmeasurements [18]. Other studies found a closerchronic disease outcomes. Correlations observedrelationship between calculated GI and glycemicbetween food choice and disease risk may also beresponses to various breakfast meals, but not all of theconfounded by behaviors related to food choices suchrelationships were predictable [19].as physical activity, calorie intake, and other dietarycomponents.Other studies found that the ingestion of milk with riceresulted in a significantly lower GI than when rice wasNevertheless, while inaccuracies in GI and GL valueseaten alone [20] while another found that when cheeseabound between individuals and inter-individually, theywas added to a potato, the potato's mean7s.e.m,may still have utility in glycemic control in diabeticdramatically reduced by 57.6% from 9378 to 3975 [21].patients. However, extreme caution should be takenwhen food choices are based solely on GI and GLData also suggests that combinations of foods canvalues, as many low GI and GL foods or meals may bemarkedly reduce the GI values while adding proteinscalorically dense but contain unhealthy amounts of fattyand fats to a carbohydrate meal can significantly reduceacids that are known to contribute to poor healthglycemic responses [22, 23]. Thus, it is clear thatoutcomes. A better understanding of the mechanismsaggregating the GI values of individual components ofbehind how different foods affect glycemic responsesa meal does not accurately predict the observed GI ofwould help improve our ability to predict these effectsthe meal as a whole.accurately. Until then, patients with diabetes and othermetabolic conditions should consult a dietitian to helpdevelop appropriate meal plans.5 DISCUSSIONQuoting the lead author of a recent study entitledThe FAO/WHO Report on Carbohydrates and Human“Estimating the reliability of glycemic index values andNutrition of 1998 suggested that the concept of GIpotential sources of methodological and biologicalvalues provided a means of selecting foods for healthvariability” published in the American Journal of Clinicaland disease prevention. The report notes three ways toNutrition, Nirupa Matthan, Ph.D., scientist in theuse this information: 1) understanding how diet affectsCardiovascular Nutrition Laboratory at the USDAindividual blood glucose levels, 2) choosingHNRCA says, ”Based on our results, we feel stronglycarbohydrates that can supply sustained energy withoutinducing glycemic responses or weight gain, and 3)avoiding dietary patterns leading to insulin resistanceand increased risk for obesity [24].However, since its publication in 1998, the increasing 2021 The Paleo Foundationthat glycemic index is impractical for use in foodlabeling or in dietary guidelines at the individual level.If your doctor told you your LDL cholesterol value couldvary by 20% (i.e., a difference between normal vs highrisk), I don't think many people would find such an issueacceptable” [25].3