Interest in the effect of proteins or amino acids on glucose metabolism dates back at least a century, largely because it was demonstrated that the amino acids from ingested protein could be converted into glucose. Indeed, these observations influenced the dietary information provided to people with diabetes. Subsequently it was shown that ingested protein did not raise the blood glucose concentration. It also was shown that proteins could stimulate a rise in insulin and glucagon but the response to various proteins was different. In addition, it was shown that individual amino acids also could stimulate a rise in insulin and in glucagon concentrations. When individual amino acids are ingested by normal subjects, there is an ordering of the insulin and glucagon responses. However, the order is not the same for insulin and glucagon. In addition, the metabolic response cannot be predicted based on the functional groups of the amino acids. Thus, empirical prediction of the metabolic response to ingested single amino acids is not possible.
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