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.
G. Mikael Fogelholm, Hannu K. Näveri, Kai T.K. Kiilavuori and Matti H.A. HärkÖnen
Luke R. Bucci, James F. Hickson Jr., Ira Wolinsky and James M. Pivarnik
Ornithine supplementation has gained popularity with athletes because of its alleged potential to release anabolic hormones, factors governing skeletal muscle hypertrophy. Three female and nine male bodybuilders sewed as subjects in a study to test the effectiveness of oral ornithine in bringing about the release of insulin, an anabolic hormone. After an overnight fast, subjects were administered 40, 100, or 170 mg·kg−1 L-ornithine.HC1 by mouth in a random fashion on three consecutive Saturday mornings. Blood samples were drawn at baseline (T=O), 45, and 90 min afterward. Serum ornithine levels were elevated (p~0.01) at T=45 and 90 min for all three dosage levels. However, serum insulin did not change from baseline levels at any dose of ornithine. The present findings show that ornithine is not an insulin secretagogue.