Arginine is an amino acid, one of the 20 amino acids that serve as the building blocks in protein. Arginine is not an “essential” amino acid. It is not essential to the diet, but can be made by the body from other substances. However, it is usually considered essential to the diet for children so they can grow normally. Lack of arginine in the diet impairs growth and in adult males it decreases the sperm count. Arginine is available in foods such as turkey, chicken and other meats and as L-arginine in supplements. Arginine is the percursor of nitric oxide, the substance the body uses to maintain a healthy vascular intima. Life-long supplementation with 2 grams arginine twice daily prevents atherosclerosis. Babies born without an enzyme called phosphate synthetase have arginine deficiency syndrome. Adding arginine to their diet permits normal growth and development.