L-Arginine is a conditionally essential basic amino acid involved primarily in urea metabolism and excretion, as well as in DNA synthesis and protein production.* It is an important precursor of Nitric Oxide (NO) and thus plays a role in the dilation of blood vessels. Sundown Naturals L-Arginine 500 mg is an ideal supplemental choice for athletes and bodybuilders in exercise and post-exercise states.* L-Arginine is one of 20 amino acids and can serve as an energy precursor to support the effects of exercise.* L-Arginine plays an important role in human nutrition, and is one of the most important amino acids for supporting heart health and coronary blood flow.