Study of the day - Dr. Carl Keen
At AdvoCare we work with a broad range of researchers and resources to stay abreast of current nutritional and health related science. Our prestigious Scientific and Medical Advisory board members also provide an invaluable insight on and evaluation of the scientific topics of the day. Today we are pleased to bring you an interesting study with accompanying review provided by Carl Keen, Ph.D., member of our board. Dr. Keen is currently Professor of Nutrition and Internal Medicine, at the University of California at Davis.
The subject of today’s review is:
The Pharmacodynamics of L-Arginine, Rainer H. Böger, American Society for Nutrition J. Nutr. 137:1650S-1655S, June 2007.
L-Arginine is a precursor for nitric oxide (NO) synthesis. NO is a ubiquitous mediator that is formed by a family of enzymes named NO synthases. In the brain, NO acts as a neurotransmitter; in the immune system, NO acts as a mediator of host defense; and in the cardiovascular system, NO mediates the protective effects of the intact endothelium, acting as a vasodilator and endogenous antiatherogenic molecule.
L-Arginine plasma levels are not significantly reduced in most disease conditions, except end-stage renal failure during hemodialysis treatment. Nonetheless, intravenous or dietary (oral) administration of relatively large doses of L-arginine has been shown to result in enhanced NO formation in subjects with impaired endothelial function at baseline.
L-Arginine appears to exert no effect in subjects with low ADMA (asymmetric dimethylarginine) levels, whereas in subjects with high ADMA levels, L-arginine restores the L-arginine/ADMA ratio to normal levels and thereby normalizes endothelial function. In conclusion, the effects of L-arginine supplementation on human physiology appear to be multicausal and dose-related. Doses of 3-8 g/d appear to be safe and not to cause acute pharmacologic effects in humans.
Dr. Keen’s assessment:
“The idea that dietary arginine supplements can improve vascular health in certain individuals has been gaining increasing acceptance by the medical profession. The review by Boger provides a concise discussion of this exciting issue in human nutrition. As commented on by Boger, the collective literature supports the idea that L-arginine supplements can, in certain cases, increase the body’s production of nitric oxide (NO), a key molecule that helps to regulate vascular function. In theory, improvements in vascular function can have multiple effects, including improvements in endurance capacity, and potentially improvements in brain blood flow. The paper by Boger provides an excellent, up to date review, on the topic of arginine supplementation, and its potential health benefits.”
