High intakes of milk, but not meat, increase s-insulin and insulin resistance in 8-year-old boys

Objective: Our objective was to examine if a high animal protein intake from milk or meat increased s-insulin and insulin resistance in healthy, prepubertal children. A high animal protein intake results in higher serum branched chain amino acids ( BCAA; leucine, isoleucine and valine) concentrations, which are suggested to stimulate insulin secretion. Furthermore, milk possesses some postprandial insulinotrophic effect that is not related to its carbohydrate content. Design: A total of 24 8-y-old boys were asked to take 53 g protein as milk or meat daily. At baseline and after 7 days, diet was registered, and insulin, glucose, and amino acids were determined. Insulin resistance and beta cell function were calculated with the homeostasis model assessment. Results: Protein intake increased by 61 and 54% in the milk- and meat-group, respectively. In the milk- group, fasting s-insulin concentrations doubled, which caused the insulin resistance to increase similarly. In the meat-group, there was no increase in insulin and insulin resistance. As the BCAAs increased similarly in both groups, stimulation of insulin secretion through BCAAs is not supported. Conclusions: Our results indicate that a short-term high milk, but not meat, intake increased insulin secretion and resistance. The long-term consequences of this are unknown. The effect of high protein intakes from different sources on glucose-insulin metabolism needs further studying.