Article

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: 3.88). 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
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    • "GL for individual food items in the dietary record was calculated as the product of diet GI and carbohydrate intake divided by 100 [23]. Dietary GL represents both the quantity and the quality of carbohydrate in diet [22] and was calculated as sum total of GL of foods consumed in the day [24]. Diet GI was calculated using the formula Diet GI= Diet GL×100/amount of carbohydrate in the diet [24]. "
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    ABSTRACT: BACKGROUND: Gestational Diabetes Mellitus (GDM) increases risks for type 2 diabetes and weight management is recommended to reduce the risk. Conventional dietary recommendations (energy-restricted, low fat) have limited success in women with previous GDM. The effect of lowering Glycaemic Index (GI) in managing glycaemic variables and body weight in women post-GDM is unknown. OBJECTIVE: To evaluate the effects of conventional dietary recommendations administered with and without additional low-GI education, in the management of glucose tolerance and body weight in Asian women with previous GDM. METHOD: Seventy seven Asian, non-diabetic women with previous GDM, between 20- 40y were randomised into Conventional healthy dietary recommendation (CHDR) and low GI (LGI) groups. CHDR received conventional dietary recommendations only (energy restricted, low in fat and refined sugars, high-fibre). LGI group received advice on lowering GI in addition. Fasting and 2-h post-load blood glucose after 75g oral glucose tolerance test (2HPP) were measured at baseline and 6 months after intervention. Anthropometry and dietary intake were assessed at baseline, three and six months after intervention. The study is registered at the Malaysian National Medical Research Register (NMRR) with Research ID: 5183 RESULTS: After 6 months, significant reductions in body weight, BMI and waist-to-hip ratio were observed only in LGI group (P<0.05). Mean BMI changes were significantly different between groups (LGI vs. CHDR: -0.6 vs. 0kg/m2, P= 0.03). More subjects achieved weight loss >=5% in LGI compared to CHDR group (33% vs. 8%, P=0.01). Changes in 2HPP were significantly different between groups (LGI vs. CHDR: median (IQR): -0.2(2.8) vs. +0.8 (2.0) mmol/L, P=0.025). Subjects with baseline fasting insulin>=2muIU/ml had greater 2HPP reductions in LGI group compared to those in the CHDR group (-1.9+/-0.42 vs. +1.31+/-1.4 mmol/L, P<0.001). After 6 months, LGI group diets showed significantly lower GI (57+/-5 vs. 64+/-6, P<0.001), GL (122+/-33 vs. 142+/-35, P=0.04) and higher fibre content (17+/-4 vs.13+/-4g, P<0.001). Caloric intakes were comparable between groups. CONCLUSION: In women post-GDM, lowering GI of healthy diets resulted in significant improvements in glucose tolerance and body weight reduction as compared to conventional low-fat diets with similar energy prescription.
    Full-text · Article · May 2013 · Nutrition Journal
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    • "Indeed, the amount and GI of carbohydrate account for ;90% of the total variability in mean blood glucose and insulin responses[27,29,30]. GL has been validated and predicts glucose responses in an approximately linear fashion[31]; it is numerically equivalent to the glycemic glucose equivalent (GGE), which is the weight of glucose in grams that would induce a glycemic response equal to that induced by food[32,33]. Specifically, Liu et al.[32]reported that foods administered at the same GGE dose produce similar glycemic responses despite up to a 2.5-fold range in carbohydrate content, and that doubling the dose doubles the response. "
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    ABSTRACT: Glycemic index (GI) and glycemic load (GL) have been independently assessed with regard to their metabolic effects and their associations with disease risk. Because a low-GI high-carbohydrate and a high-GI low-carbohydrate food/meal can produce the same GL, we propose that these 2 concepts should be used in conjunction to characterize the carbohydrate quality of mixed meals. The aim of this study was to measure postprandial glucose, insulin, and cortisol responses of meals differing in both GI and GL over a period of 3 hours (every 15 minutes for the first hour, and every 30 minutes subsequently), and to investigate the validity of methods of calculating GI and GL by measuring the cumulative incremental area under the curve (iAUC) for glucose and insulin (0-2 hours and 2-3 hours postprandially). A total of 10 healthy lean young adults (5 males, 5 females) participated. Breakfast meals were designed to differ in terms of GI and GL based on a 2 × 2 grid with a single elaboration: low-GI high-GL (M1); high-GI high-GL (M2a) of similar GL to M1; high-GI high-GL (M2b) of similar macronutrient composition to M1 (the elaboration); low-GI low-GL (M3); and high-GI low-GL (M4). The 5 breakfast meals were administered in a double-blind randomized crossover design. Repeated measures analysis of variance was performed to investigate differences in metabolic response between low- versus high-GI and between low- versus high-GL breakfast meals (and GI × GL interactions), with GI and GL used as within-subject factors. High-GL meals increased glucose iAUC and insulin iAUC in both immediate (0-2 hours) (p < 0.01, p < 0.001, respectively) and middle postabsorptive periods (2-3 hours) (p = 0.04, p = 0.02, respectively) compared with low-GL meals. GI meals were not associated with glucose iAUC 0 to 2 hours (p = 0.37) and 2 to 3 hours (p = 0.81) postprandially. GI meals were not associated with insulin iAUC 0 to 2 hours postprandially (p = 0.81); in contrast, high-GI meals increased insulin iAUC 2 to 3 hours postprandially (p = 0.03) compared with low-GI meals. No significant differences were noted in cortisol responses, GI × GL interactions, or effect modification by gender. These findings highlight the need for further investigation of meals/diets differing in both GI and GL to characterize metabolic responses and potential health effects.
    Full-text · Article · Apr 2011 · Journal of the American College of Nutrition
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    • "This is perhaps counterintuitive, because the blood glucose AUC does not increase in direct proportion to the amount consumed. For example, eating six times the amount of bread results in an approximately threefold increase in AUC (Brand-Miller et al., 2003c). In other words, as the amount of food increased, the rate of increase in AUC declines, an effect shown in Figure 2 (Venn et al., 2006). "
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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.
    Full-text · Article · Jan 2008 · European Journal of Clinical Nutrition
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