Market research suggests that l-arginine is a very popular amino acid supplement among male students. L-arginine is a conditionally essential amino acid that’s involved in several metabolic pathways. Accordingly, a typical western diet provides approximately 3-6 g of l-arginine per day .
L-Arginine and Growth Hormone
For athletes, two of the most important pathways include its conversion to nitric oxide (NO) via nitric oxide synthase and its stimulation of growth hormone. Nitric oxide is of interest due to its vasodilatory properties and its ability to increase blood flow.
L-arginine has previously been shown to increase the release of growth hormone (GH) . The anabolic effects of GH have been widely validated in research studies and include lipolysis as well as increases in insulin and IGF-1. In the news, numerous athletes involved in doping scandals have been tied to GH.
Research on L-Arginine
Previous research has demonstrated that intravenous infusion of l-arginine results in increases in both NO and GH in a dose-dependent manner . However, IV infusion is not an option for most athletes and they generally consume l-arginine in oral form. When ingested orally, research has found somewhat conflicting results regarding supplementation with l-arginine and its effects on increasing NO and GH.
Researchers from the University of Alberta, my alma mater, recently studied the effects of high and low dose oral boluses of l-arginine in physically active subjects on plasma l-arginine concentrations as well as its ability to stimulate increases in NO, GH, insulin, and IGF-1 .
The study itself employed a randomized double-blind placebo control design and included 14 physically active male volunteers (25+/- 5 years). For the l-arginine supplement, the article notes that it was purchased at a General Nutrition Centre.
Though they found that the low dose bolus (0.075 g/kg of body mass) was just as effective as the high dose bolus (.15 g/kg of body mass of l-arginine) at increasing plasma l-arginine concentrations, neither dose resulted in increases in NO, GH, insulin, or IGF-1.
“This study was able to establish that 2 different relative doses of orally administered L-arginine significantly elevated plasma L-arginine concentrations at rest. However, neither dose was sufficient to increase any metabolite or hormone measured at rest. Future research is needed to assess the ergogenic potential of L-arginine consumption when combined with acute exercise stimuli.”
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- Forbes SC, Bell GJ. The acute effects of a low and high dose of oral l-arginine supplementation in young active males at rest. Appl Physiol Nutr Metab. 2011 Jun;36(3):405-11. Epub 2011 May 16.