title: High-carbohydrate-low-glycaemic index dietary advice improves glucose disposition index in subjects with impaired glucose tolerance.
abstract: Controversy exists about the optimal amount and source of dietary carbohydrate for managing insulin resistance. Therefore, we compared the effects on insulin sensitivity (SI), pancreatic responsivity (AIRglu) and glucose disposition index of dietary advice aimed at reducing the amount or altering the source of dietary carbohydrate in subjects with impaired glucose tolerance (IGT). Subjects were randomized to high-carbohydrate-high-glycaemic index (GI) (high-GI, n 11), high-carbohydrate-low-GI (low-GI, n 13), or low-carbohydrate-high-monounsaturated fat (MUFA, n 11) dietary advice, with SI, AIRglu and DI measured using a frequently sampled, intravenous glucose tolerance test before and after 4 months treatment. Carbohydrate and fat intakes and diet GI, respectively, were: high-GI, 53 %, 28 %, 83; low-GI, 55 %, 25 %, 76; MUFA, 47 %, 35 %, 82. Weight changes on each diet differed significantly from each other: high-GI, -0.49 (sem 0.29) kg; low-GI, -0.19 (sem 0.40) kg; MUFA +0.27 (sem 0.45) kg. Blood lipids did not change, but glycated haemoglobin increased significantly on MUFA, 0.02 (sem 0.11) %, relative to low-GI, -0.19 (sem 0.08) %, and high-GI, -0.13 (sem 0.14) %. Diastolic blood pressure fell by 8 mmHg on low-GI relative to MUFA (P=0.038). Although SI and AIRglu did not change significantly, DI, a measure of the ability of beta-cells to overcome insulin resistance by increasing insulin secretion, increased on low-GI by >50 % (P=0.02). After adjusting for baseline values, the increase in DI on low-GI, 0.17 (sem 0.07), was significantly greater than those on MUFA, -0.09 (sem 0.08) and high-GI, -0.03 (sem 0.02) (P=0.019). Thus, the long-term effects of altering the source of dietary carbohydrate differ from those of altering the amount. High-carbohydrate-low-GI dietary advice improved beta-cell function in subjects with IGT, and may, therefore, be useful in the management of IGT.
authors: Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Canada M5S 3E2. thomas.wolever@utoronto.ca
authors: Thomas M S
authors: TM
authors: Wolever
authors: Christine
authors: C
authors: Mehling
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D002149:Energy Intake; D005229:Fatty Acids, Monounsaturated / Q000008:administration & dosage; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D000078790:Insulin Secretion; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D005229:Fatty Acids, Monounsaturated; D006442:Glycated Hemoglobin; D007328:Insulin