Effect of Pre-breakfast Whey Protein Supplement on Post-breakfast Glycaemic Excursion and Insulinotropic Response in Type 2 Diabetes Mellitus.

Abstract

Introduction: Postprandial glucose excursions can contribute to increased cardiovascular risk, microvascular complications, and glycaemic variability in type 2 diabetes mellitus (T2DM). Nutritional interventions play a major role. Whey protein, known for its insulinotropic and incretin-stimulating effects, could be an effective supplement. The objective of the study was to evaluate the acute effects of pre-breakfast whey protein supplementation on postprandial glucose, insulin, GLP-1, and C-peptide responses in patients with T2DM.

Methods: This single-centre, prospective, within-subject comparative study included two test visits per participant: a water pre-load (control) and a whey protein pre-load (30 g in 250 mL water) given 30 min before breakfast. Uniform breakfast and lunch meals were provided, and blood samples were collected up to 2 h after lunch. Plasma glucose, insulin, GLP-1, and C-peptide were recorded, and the incremental area under the curve (iAUC) was calculated.

Results: Ten patients with T2DM were studied (mean age 47.8 years, body mass index 29.2 kg/m², glycated haemoglobin 7.4%, disease duration 3.2 years). Compared with water, whey protein significantly reduced post-breakfast and post-lunch glucose excursions (glucose iAUC 48,329 vs. 54,743; P < 0.01) and increased insulin (13,377 vs. 9,492; P < 0.01), GLP-1 (18,803 vs. 12,814; P < 0.01), and C-peptide (1860 vs. 1535; P < 0.01) iAUCs. The effect persisted through the second meal.

Conclusion: Pre-breakfast whey protein supplementation reduced postprandial glucose excursions and enhanced insulin and incretin responses in T2DM. It may serve as a practical and low-cost dietary approach to improve postprandial glycaemic control.