Physiological validation of the concept of glycemic load in lean young adults.

Human Nutrition Unit, School of Molecular and Microbial Biosciences, University of Sydney, Sydney, NSW, Australia.
Journal of Nutrition (Impact Factor: 4.23). 09/2003; 133(9):2728-32.
Source: PubMed

ABSTRACT Dietary glycemic load, the mathematical product of the glycemic index (GI) of a food and its carbohydrate content, has been proposed as an indicator of the glucose response and insulin demand induced by a serving of food. To validate this concept in vivo, we tested the hypotheses that 1). portions of different foods with the same glycemic load produce similar glycemic responses; and 2). stepwise increases in glycemic load for a range of foods produce proportional increases in glycemia and insulinemia. In the first study, 10 healthy subjects consumed 10 different foods in random order in amounts calculated to have the same glycemic load as one slice of white bread. Capillary blood samples were taken at regular intervals over the next 2 h. The glycemic response as determined by area under the curve was not different from that of white bread for nine foods. However, lentils produced lower than predicted responses (P < 0.05). In the second study, another group of subjects was tested to determine the effects of increasing glycemic load using a balanced 5 x 5 Greco-Latin square design balanced for four variables: subject, dose, food and order. Two sets of five foods were consumed at five different glycemic loads (doses) equivalent to one, two, three, four and six slices of bread. Stepwise increases in glycemic load produced significant and predictable increases in both glycemia (P < 0.001) and insulinemia (P < 0.001). These findings support the concept of dietary glycemic load as a measure of overall glycemic response and insulin demand.

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Available from: Jennie C Brand-Miller, Jun 28, 2015
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    ABSTRACT: Glycemic index (GI) describes the blood glucose response after consumption of a carbohydrate containing test food relative to a carbohydrate containing reference food, typically glucose or white bread. GI was originally designed for people with diabetes as a guide to food selection, advice being given to select foods with a low GI. The amount of food consumed is a major determinant of postprandial hyperglycemia, and the concept of glycemic load (GL) takes account of the GI of a food and the amount eaten. More recent recommendations regarding the potential of low GI and GL diets to reduce the risk of chronic diseases and to treat conditions other than diabetes, should be interpreted in the light of the individual variation in blood glucose levels and other methodological issues relating to measurement of GI and GL. Several factors explain the large inter- and intra-individual variation in glycemic response to foods. More reliable measurements of GI and GL of individual foods than are currently available can be obtained by studying, under standard conditions, a larger number of subjects than has typically been the case in the past. Meta-analyses suggest that foods with a low GI or GL may confer benefit in terms of glycemic control in diabetes and lipid management. However, low GI and GL foods can be energy dense and contain substantial amounts of sugars or undesirable fats that contribute to a diminished glycemic response. Therefore, functionality in terms of a low glycemic response alone does not necessarily justify a health claim. Most studies, which have demonstrated health benefits of low GI or GL involved naturally occurring and minimally processed carbohydrate containing cereals, vegetables and fruit. These foods have qualities other than their immediate impact on postprandial glycemia as a basis to recommend their consumption. When the GI or GL concepts are used to guide food choice, this should be done in the context of other nutritional indicators and when values have been reliably measured in a large group of individuals.
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    ABSTRACT: Summary in English. Includes bibliographical references. Thesis (MDietetics--Faculty of Health Sciences)-University of Pretoria, 2006.
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    ABSTRACT: Carbohydrates are a major energy source for the human body and particularly glucose is the only energy source for the brain. Thus glucose metabolism is important to maintain normal brain function. Evidence showed insulin resistance and diabetes are associated with cognitive decline and a large amount of highly processed carbohydrate intake; in other words, a high glycemic load diet, which increases blood glucose faster and insulin demand, is associated with increased risk of insulin resistance and diabetes. Based on this premise, the hypothesis that a high glycemic load (GL) diet increases the risk of incident Alzheimer’s disease (AD) was examined among Cache County elderly people in Northern Utah. At the baseline survey, 3,831 participants 65 years of age or older completed a food frequency questionnaire (FFQ) and cognitive screening. Observation time to collect the data for incident AD was approximately 10 years. Incident AD was determined by final consensus conference after multi-steps of screening. GL was calculated as the product of carbohydrate intake and glycemic index (GI) and adjusted for energy intake. FFQs from diabetics were considered to be invalid to assess dietary carbohydrates intake and excluded. The analysis was examined separately by gender.The Cox proportional hazard regression model in survival analysis was used to relate GL to incident AD using a time variable with age of AD onset. There was no association in men but a negative association in women in the unadjusted model. Evidence of confounding by total kcal was apparent in women, particularly in the lowest GL group, which had the highest total kcal mean intake. Finally no association between GL and AD was found after adjustment for education, myocardial infarction (MI), stroke, Body Mass Index (BMI), physical activity, smoking, alcohol use, APOE ε-4 alleles, multi-vitamins use, total kcal, and controlling interaction between GL and total kcal.The low GL group had unique characteristics in lifestyle factors, macro-nutrients intake, and pattern of food use. The inverse relationship between GL and total kcal may partly be explained by lifestyle factors, particularly alcohol intake. The characteristics of low GL group, current smokers, alcohol users, and their relationship and interaction between total kcal and risk of AD should be explored further.