Failure of Commercial Oral Amino Acid Supplements to Increase Serum Growth Hormone Concentrations in Male Body-Builders

in International Journal of Sport Nutrition and Exercise Metabolism
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Amino acids are commonly ingested as ergogenic aids in the belief that they enhance protein synthesis and stimulate growth hormone release. The aim of this study was to determine the acute effect that amino acid supplements have on serum growth hormone (GH) concentration. Seven male bodybuilders reported to the laboratory on four occasions after an 8-hr fast and ingested, in random order, either a placebo, a 2.4-g arginine/lysine supplement, a 1.85-g ornithine/tyrosine supplement, or a 20-g BovrilR drink. Blood was collected before each treatment and again every 30 minutes for 3 hours for the measurement of serum GH concentration. On a separate occasion, subjects had an intravenous infusion of 0.5 fig GH-releasing hormone-kg ' body weight to confirm that GH secretory response was normal. The main finding was that serum GH concentrations were not altered consistently in healthy young males following the ingestion of the amino acid supplements in the quantities recommended by the manufacturers.

Lambert and Macfarlane are with the MRC/UCT Bioenergetics of Exercise Research Unit, Dept. of Physiology, University of Cape Town Medical School, Cape Town, 7925, South Africa. Hefer is with the Dept. of Dietetics, University of Cape Town Medical School. Millar is with the MRC Regulatory Peptides Research Unit. Dept. of Chemical Pathology, University oP Cape Town Medical School.