A total of 14 individuals with type 2 diabetes were served a high-GI breakfast (white bread) and subsequent high-GI lunch (mashed potatoes with meatballs). Whey supplementation was provided with both meals on one day, and whey was exchanged for lean ham and lactose on another day.

The investigators took blood samples before and during a 4-hour period after breakfast and 3 hours after lunch in order to measure blood glucose, insulin, and other factors.

The insulin responses were higher after both breakfast (31%) and lunch (57%) when the meals were supplemented with whey compared to when whey was not included. The blood glucose response was significantly reduced (-21%; 180 min area under the curve) after the lunch meal was supplemented with whey.

The team observed higher postprandial GIP responses after whey ingestion. No differences were observed in GLP-1 between the reference and test meals.

The lesser effect on insulin of whey after breakfast, "in combination with the fact that the insulin resistance may be higher in the morning after the overnight fast, may explain the inability of whey to reduce the blood glucose increment after breakfast," Nilsson's team explains.