L-Arginine is a conditionally essential amino acid found in the diet. It is a dietary supplement used mostly by athletic people because it is the amino acid that directly produces nitric oxide via the nitric oxide synthase enzymes.
It's particularly important during periods of illness and chronic conditions like hypertension and type II diabetes, as these states tend to be characterized by an increase in the enzyme that degrades L-arginine (known as arginase) resulting in a transient deficiency; this precedes an increase in blood pressure in these states, and can be partially remedied by an increase in L-arginine intake or resolution of the illness/disease state.
L-arginine is a popular supplement for athletes as it is touted to increase nitric oxide activity in the body.
Blood flow: “Supplementation of 8g of arginine twice daily (16g total) for 6 weeks in persons with intermittent claudication appears to promote blood flow and reduce symptoms associated with increased biomarkers of nitric oxide metabolite (nitrate and urinary cGMP). Functional testing noted that arginine outperformed 80mcg PGE1 in improving walking distance and pain-free walking distance, and improved VAS scores for symptoms.” Böger, R. H., Bode-Böger, S. M., Thiele, W., Creutzig, A., Alexander, K., & Frölich, J. C. (1998, November). Restoring vascular nitric oxide formation by L-arginine improves the symptoms of intermittent claudication in patients with peripheral arterial occlusive disease. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/9809945
Nitro oxide:”Supplemental arginine for 3 days at 6g, relative to placebo, was able to enhance nitric oxide production and decrease oxygen consumption (7%) while improving time to exhaustion (24.8%) in otherwise healthy men.” Stephen J. Bailey, Paul G. Winyard, Anni Vanhatalo, Jamie R. Blackwell, Fred J. DiMenna. “Acute l-Arginine Supplementation Reduces the O2 Cost of Moderate-Intensity Exercise and Enhances High-Intensity Exercise Tolerance.” Journal of Applied Physiology, www.physiology.org/doi/full/10.1152/japplphysiol.00503.2010.
Insulin sensitivity: “In persons with impaired glucose tolerance where 6.4g L-arginine was given daily for 18 months (followed by 12 months of followup), supplementation was associated with improved fat mass and lean mass (increase in lean mass was 0.12+/-1.97, and only statistically significant when compared to the loss seen with placebo) and associated with improved insulin secretion following a test meal.”Monti, L. D., Setola, E., Lucotti, P. C., Marrocco-Trischitta, M. M., Comola, M., Galluccio, E., . . . Piatti, P. M. (2012, October). Effect of a long-term oral l-arginine supplementation on glucose metabolism: A randomized, double-blind, placebo-controlled trial. Retrieved from