Certain amino acids are effective secretagogues of insulin and have been found to synergistically increase the blood insulin response to a
carbohydrate load when administered in combination (Floyd et al. 1966; Fajans et al. 1967). Of the 20 amino acids normally found in protein, the most effective insulin secretagogue is arginine (Fajans et al. 1967). When infused with carbohydrate, arginine has been found to increase the insulin response fivefold above that produced by the carbohydrate or arginine alone. However, we have found the use of amino acids to be impractical when added to a carbohydrate supplement because they produce many unwanted sideeffects such as mild borborygmus and diarrhoea.
Protein meals and supplements also have been found to enhance the insulin response to a carbohydrate load and do not produce the unwanted side-effects of the amino acids (Rabinowitz et al. 1966; Pallota & Kennedy 1968; Spiller et al. 1987). For example, Spiller et al. (1987) demonstrated a nincreased blood insulin response and decreased blood glucose response with the addition of protein to a 58 g carbohydrate supplement. The insulin response was found to be directly proportional and the glucose response inversely proportional to the protein content of the
carbohydrate–protein supplement. No adverse side-effects were reported.