**Abstract**

It is not known whether the administration of glucose or sucrose influences plasma levels of amino acids. We want to know whether plasma levels of amino acids and if the administration of glucose or sucrose are different in young and old men and are influenced by the administration of glucose or sucrose. We found that the levels of most amino acids in plasma are lower in old men than young men. When sucrose was administered to old men, levels of total amino acids decreased significantly in old men. In both old and young men plasma levels of total nonessential amino acids significantly decreased at 120 min. after the administration of glucose but not sucrose. On the other hand, total essential and branched amino acids levels decreased significantly after the administration of both glucose and sucrose in young and old men. From these results, responses to the administration of glucose were different from the response to sucrose between young and old men. Also glucose was more effective in decreasing plasma levels of various amino acids. These results seem to suggest that glucose was more effective in stimulating insulin release and young men were more responsive to sugar than old men in stimulating insulin release.

**Keywords:** amino acids, branched chain amino acids, tryptophan, serotonin, leucine, appetite, feeding
