Glutamate is central to several transamination reactions that affect the production of ammonia, alanine, glutamine as well as tricarboxylic acid (TCA) cycle intermediates during exercise. To further study glutamate metabolism, we administered 150mg/kg(bw) of monosodium glutamate (MSG) and placebo (PLB) to 7 male subjects who then either rested or exercised (15 min cycling at ~85% VO_2max). MSG ingestion resulted in elevated plasma glutamate, aspartate and taurine both at rest and during exercise (P<0.05) while most other amino acids were unchanged. Neither plasma alanine nor ammonia was altered at rest. During exercise and following glutamate ingestion, alanine was increased (P<0.05) and ammonia was attenuated (P<0.05). Glutamine was also elevated following glutamate ingestion during rest and exercise trials. MSG administration also resulted in elevated insulin levels (P<0.05) which were parallel to the trend in C-peptide levels. Thus, MSG can successfully elevate plasma glutamate both at rest and during exercise. The plasma amino acid responses suggest that increased glutamate availability during exercise alters its distribution in transamination reactions within active muscle which results in elevated alanine and decreased ammonia levels.