Vascular effects of dietary L-arginine supplementation

The vascular endothelium is acknowledged to play an important role in vascular physiology. Attention has focused on endothelial production of nitric oxide as a key element in many of the processes associated with the development of atherosclerosis. L-arginine is the substrate for the enzyme nitric oxide synthase (NOS), which is responsible for the endothelial production of nitric oxide. Therefore, many investigators have been interested in whether dietary L-arginine supplementation can augment nitric oxide production and thereby improve vascular health. The effects of oral L-arginine on vascular health and disease have been examined both in human beings and in various animal models. In this review, we summarize the results of studies of oral L-arginine supplementation on atherosclerotic lesion formation, as well as markers of endothelial function (e.g. macrophage function, platelet aggregation and adhesion, and in vitro vascular ring studies). Although results of oral L-arginine supplementation in hypercholesterolemic animals have generally shown beneficial effects, the data in humans are varied, possibly because of small sample sizes and brief periods of study. Long-term randomized clinical trials are needed to more definitively address whether oral L-arginine supplementation could be advantageous for vascular health.