Main content area

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

Malin, Steven K., Kullman, Emily L., Scelsi, Amanda R., Godin, Jean‐Philippe, Ross, Alastair B., Kirwan, John P.
Molecular nutrition & food research 2019 v.63 no.7 pp. e1800967
adults, body mass index, c-peptide, diet, ghrelin, glucagon-like peptide 1, glucose, insulin resistance, insulin secretion, islets of Langerhans, noninsulin-dependent diabetes mellitus, whole grain foods
INTRODUCTION: The effect of whole‐grain (WG) versus refined‐grain (RG) diets on glucose‐stimulated insulin secretion (GSIS) and β‐cell function is unclear. METHODS: In a double‐blind crossover randomized controlled trial, 13 prediabetic adults (37.2 ± 1.8 y, BMI: 33.6 ± 1.4 kg m⁻², 2 h glucose: 146.9 ± 11.6 mg dL⁻¹) are provided isocaloric‐matched WG and RG diets for 8‐weeks each, with an 8–10 week washout between diets. Glucose, insulin, and C‐peptide are studied over 240 min following a 75 g OGTT. Incretins (GLP‐1 and GIP), PYY, and total ghrelin are assessed at 0, 30, and 60 min. Mixed‐meal diets for carbohydrate (54%), fat (28%), and protein (18%) contain either WG (50 g/1000 kcal) or equivalent RG. RESULTS: Both diets induce fat loss (≈2 kg). While neither diet impacts early phase GSIS, the WG diet increases total GSIS (iAUC of C‐peptide₀‐₂₄₀/Glc₀‐₂₄₀, p = 0.02) and β‐cell function (disposition index; GSIS × insulin sensitivity, p = 0.02). GIP and PYY are unaltered by either diet, but GLP‐1 is higher at 30 min following RG versus WG (p = 0.04). Ghrelin levels are higher at 60 min of the OGTT following both interventions (p = 0.01). CONCLUSION: A WG‐rich diet increases β‐cell function independent of gut hormones in adults with prediabetes.