Plasma insulin responses after ingestion of different amino acid or protein mixtures with carbohydrate

Background: Protein induces an increase in insulin concentrations when inge sted in combination with carbohydrate. Increases in plasma insulin concentr ations have been observed after the infusion of free amino acids. However, the insulinotropic properties of different amino acids or protein (hydrolys ates) when coingested with carbohydrate have not been investigated. Objective: The aim of this study was to define an amino acid and protein (h ydrolysate) mixture with a maximal insulinotropic effect when co-ingested w ith carbohydrate. Design: Eight healthy, nonobese male subjects visited our laboratory, after an overnight fast, on 10 occasions on which different beverage composition s were tested for 2 h. During those trials the subjects ingested 0.8 g kg(- 1) . h(-1) carbohydrate and 0.4 g . kg(-1) . h(-1) of an amino acid and pro tein (hydrolysate) mixture. Results: A strong initial increase in plasma glucose and insulin concentrat ions was observed in all trials, after which large differences in insulin r esponse between drinks became apparent. After we expressed the insulin resp onse as area under the curve during the second hour, ingestion of the drink s containing free leucine, phenylalanine, and arginine and the drinks with free leucine, phenylalanine, and wheat protein hydrolysate were followed by the largest insulin response (101% and 103% greater, respectively, than wi th the carbohydrate-only drink; P < 0.05). Conclusions: Insulin responses are positively correlated with plasma leucin e, phenylalanine, and tyrosine concentrations. A mixture of wheat protein h ydrolysate, free leucine, phenylalanine, and carbohydrate can be applied as a nutritional supplement to strongly elevate insulin concentrations.