ARGININE ASPARTATE SUPPLEMENTATION IN MARATHON RUNNERS REDUCES TOTAL PLASMA AMINO ACID LEVEL

Abstract

706 The metabolic influence of a 14 day long supplementation to the habitual diet with L-arginine-L-aspartate (15 g daily) was investigated in 14 endurance-trained athletes during a non-competitive marathon run. In this double-blind crossover field study, specific blood parameters and the respiratory exchange ratio were analyzed before the run, after 31 km, at the end of the run, and after a recovery period of two hours. The supplementation caused no significant change in the plasma level of carbohydrate (glucose, lactate, pyruvate) and fat metabolites (fatty acids, glycerol, β-hydroxybutyrate). However, the plasma level of urea and arginine was significantly increased, and the level of most of the remaining plasma amino acids was significantly reduced. The plasma level of ammonia, lactate dehydrogenase, and creatine kinase as well as the respiratory exchange ratio was unaffected by the treatment. The plasma level of cortisol and insulin did not change either, but somatotropic hormone and glucagon were significantly higher during the exercise bout with the arginine aspartate treatment. The metabolic impact of the supplementation had no influence on the running time. Since in humans the metabolic effects of a plasma amino acid imbalance (increased arginine, decreased total amino acid level) are not known, the practice of using single amino acid supplements as potential ergogenics should be critically reevaluated.