The Dose Effect of Whey Protein on Glycemic Control in Adults with Insulin Resistance

Whey protein coupled with a glucose challenge increases insulin secretion and may decrease glucose responses in people with pre-diabetes and type 2 diabetes. These responses may be attributed to whey protein’s effect on the incretins glucagon-like peptide-1 (GLP-1) and glucose dependent insulinotropic polypeptide (GIP). The purpose of this study was to examine the effect of various doses of whey protein on postprandial glycemic control and incretin responses. Participants with insulin resistance (n=9, mean ± SD; age: 64.3 + 8.1 yrs; BMI: 29.4 + 6.0 kg/m2; fasting plasma glucose: 6.9 + 1.2 mmol/l; HbA1c: 6.4 + 0.6%) completed three randomized treatments. Treatment 1 included 250 ml water + 20 g whey protein (T1), and treatment 2 included 250 ml water + 30 g whey protein (T2). The control treatment included 250 ml water (CON). Each treatment was followed by a 50 g oral glucose tolerance test. Incremental area under the curve (iAUC) for insulin increased from CON to T1 (P<0.01, 45.5%), CON to T2 (P<0.01, 61.0%), and T1 to T2 (P<0.01, 28.5%), with a significant decrease in postprandial AUC for glucose with T2 (P=0.04, -41.2%). Neither GIP nor GLP-1 iAUC increased with T1 or T2 compared to CON. However, postprandial glucose iAUC was significantly reduced for T2 compared to CON (P=0.04, -41.2%). There was a dose effect of whey protein on plasma insulin with a significant decrease in postprandial glucose iAUC following T2. Thirty grams of a whey protein preload may be adequate to provide postprandial glycemic improvements in the disease management of type 2 diabetes or pre-diabetes