Low-Dose Amino Asid Supplementation: No Effects on Serum Human Growth Hormone and Insulin in Male Weightlifters

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 x time interaction: p = 0.43-0.55). Analogously, serum insulin levels were not higher after amino acid supplementation. Therefore the ergogenic value of low-dose oral amino acid supplementation in increasing hGH or insulin secretion seems questionable.