GNC L-Arginine 1000 mg - Caplets The amino acid arginine has several roles in the body such as helping remove ammonia from the body which is a waste product of protein metabolism. Arginine is also an essential precursor of nitric oxide which helps maintain blood vessel tone. Essential precursor of nitric oxide. Helps maintain healthy blood vessel tone. 90 caplets / 90 servings These statements have not been evaluated by the Food & Drug Administration. This product is not intended to diagnose treat cure or prevent any disease.