Using a double-blind, crossover protocol, we studied the possible effects of a 4-day combined L-arginine, L-ornithine, and L-lysine supplementation (each 2 g/day, divided into two daily doses) on 24-hr level of serum human growth hormone (hGH) and insulin in 11 competitive weightlifters, ages 19 to 35 yrs. Three similar daily hGH peaks, seemingly preceded by a decrease in serum insulin concentration, were found during both amino acid and placebo supplementation. Supplementation did not affect the physiological variation of serum hGH concentration (treatment and treatment × time interaction: p=0.43–0.55). Analogously, serum insulin levels were not higher after amino acid supplementation. Therefore the ergogenic value of lowdose oral amino acid supplementation in increasing hGH or insulin secretion seems questionable.
The authors are with the University of Helsinki. Fogelholm is with the Dept. of Applied Chemistry and Microbiology, Div. of Nutrition, SF-00014 University of Helsinki, Finland. Näveri and Kiilavuori are with the First Department of Medicine. Harkonen is with the Department of Clinical Chemistry.