A Whole-Grain Diet Increases Glucose-Stimulated Insulin Secretion Independent of Gut Hormones in Adults at Risk for Type 2 Diabetes.

INTRODUCTION: Few data exist examining the effects of whole grain (WG) versus refined grain (RG) diets on glucose-stimulated insulin secretion (GSIS) and β-cell function.

METHODS: In a double-blind crossover randomized controlled trial, 13 sedentary prediabetic adults (37.2±1.8 y, BMI: 33.6±1.4 kg/m2 , 2h glucose: 146.9±11.6 mg/dl) were provided isocaloric-matched WG and RG diets for 8-weeks each, with an 8-10 week washout between diets. Glucose, insulin and C-peptide metabolism was studied over 240 min following a 75g OGTT. Incretins (GLP-1 and GIP), PYY, and total ghrelin were assessed at 0, 30 and 60 min. Mixed-meal diets for carbohydrate (54%), fat (28%), and protein (18%) contained either WG (50g/1000 kcal) or equivalent RG.

RESULTS: Both diets induced fat loss (∼2 kg). While neither diet impacted early phase GSIS, the WG diet increased total GSIS (iAUC of C-peptide0-240 /Glc0-240 , P = 0.02) and β-cell function (disposition index; GSIS x insulin sensitivity, P = 0.02). GIP and PYY were unaltered by either diet, but GLP-1 was higher at 30 min following RG versus WG (P = 0.04). Ghrelin levels were higher at 60 min of the OGTT following both diet interventions (P = 0.01).

CONCLUSION: A WG-rich diet increases β-cell function independent of gut hormone responses in adults with prediabetes. This article is protected by copyright. All rights reserved.