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Food insulin index: physiologic basis for predicting insulin demand evoked by composite meals.
Bao, J, de Jong, V, Atkinson, F, Petocz, P, Brand-Miller, JC
The American journal of clinical nutrition. 2009;(4):986-92
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Abstract
BACKGROUND Diets that provoke less insulin secretion may be helpful in the prevention and management of diabetes. A physiologic basis for ranking foods according to insulin "demand" could therefore assist further research. OBJECTIVE We assessed the utility of a food insulin index (FII) that was based on testing isoenergetic portions of single foods (1000 kJ) in predicting the insulin demand evoked by composite meals. DESIGN Healthy subjects (n = 10 or 11 for each meal) consumed 13 different isoenergetic (2000 kJ) mixed meals of varying macronutrient content. Insulin demand predicted by the FII of the component foods or by carbohydrate counting and glycemic load was compared with observed insulin responses. RESULTS Observed insulin responses (area under the curve relative to white bread: 100) varied over a 3-fold range (from 35 +/- 5 to 116 +/- 26) and were strongly correlated with insulin demand predicted by the FII of the component foods (r = 0.78, P = 0.0016). The calculated glycemic load (r = 0.68, P = 0.01) but not the carbohydrate content of the meals (r = 0.53, P = 0.064) also predicted insulin demand. CONCLUSIONS The relative insulin demand evoked by mixed meals is best predicted by a physiologic index based on actual insulin responses to isoenergetic portions of single foods. In the context of composite meals of similar energy value, but varying macronutrient content, carbohydrate counting was of limited value.
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Physiological validation of the concept of glycemic load in lean young adults.
Brand-Miller, JC, Thomas, M, Swan, V, Ahmad, ZI, Petocz, P, Colagiuri, S
The Journal of nutrition. 2003;(9):2728-32
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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Effect of low-glycemic-index dietary advice on dietary quality and food choice in children with type 1 diabetes.
Gilbertson, HR, Thorburn, AW, Brand-Miller, JC, Chondros, P, Werther, GA
The American journal of clinical nutrition. 2003;(1):83-90
Abstract
BACKGROUND The practicality of diets with a low glycemic index (GI) is controversial. Theoretically, low-GI diets may limit food choice and increase dietary fat intake, but there is little objective evidence to support such a theory. OBJECTIVE The objective was to determine the effect of low-GI dietary advice on dietary quality and food choice in children with diabetes. DESIGN Children aged 8-13 y with type 1 diabetes (n = 104) were recruited to a prospective, randomized study comparing the effects of traditional carbohydrate-exchange dietary advice (CHOx) with those of more flexible low-GI dietary advice (LowGI). We determined the effect on long-term macronutrient intake and food choice with the use of 3-d food diaries. RESULTS There were no differences in reported macronutrient intakes during any of the recording periods. After 12 mo, intakes of dietary fat (33.5 +/- 5.6% and 34.2 +/- 6.7% of energy, P = 0.65), carbohydrate (48.8 +/- 5.4% and 48.6 +/- 6.5% of energy, P = 0.86), protein (17.6 +/- 2.5% and 17.3 +/- 3.7% of energy, P = 0.61), total sugars, and fiber did not differ significantly between the CHOx and LowGI groups, respectively. The average number of different carbohydrate food choices per day also did not differ significantly. Subjects in the lowest-GI quartile consumed less carbohydrate as potato and white bread, but more carbohydrate as dairy-based foods and whole-grain breads than did subjects in the highest-GI quartile. CONCLUSION Children with diabetes who receive low-GI dietary advice do not report more limited food choices or a diet with worse macronutrient composition than do children who consume a traditional carbohydrate-exchange diet.
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The effect of flexible low glycemic index dietary advice versus measured carbohydrate exchange diets on glycemic control in children with type 1 diabetes.
Gilbertson, HR, Brand-Miller, JC, Thorburn, AW, Evans, S, Chondros, P, Werther, GA
Diabetes care. 2001;(7):1137-43
Abstract
OBJECTIVE To determine the long-term effect of low glycemic index dietary advice on metabolic control and quality of life in children with type 1 diabetes. RESEARCH DESIGN AND METHODS Children with type 1 diabetes (n = 104) were recruited to a prospective, stratified, randomized, parallel study to examine the effects of a measured carbohydrate exchange (CHOx) diet versus a more flexible low-glycemic index (GI) dietary regimen on HbA(1c) levels, incidence of hypo- and hyperglycemia, insulin dose, dietary intake, and measures of quality of life over 12 months. RESULTS At 12 months, children in the low-GI group had significantly better HbA(1c) levels than those in the CHOx group (8.05 +/- 0.95 vs. 8.61 +/- 1.37%, P = 0.05). Rates of excessive hyperglycemia (>15 episodes per month) were significantly lower in the low-GI group (35 vs. 66%, P = 0.006). There were no differences in insulin dose, hypoglycemic episodes, or dietary composition. The low-GI dietary regimen was associated with better quality of life for both children and parents. CONCLUSIONS Flexible dietary instruction based on the food pyramid with an emphasis of low-GI foods improves HbA(1c) levels without increasing the risk of hypoglycemia and enhances the quality of life in children with diabetes.