L-arginine plays important roles in the metabolism of an organism. It is the precursor for the synthesis of proteins and other molecules of great biological importance, including nitric oxide, ornithine, polyamines, agmatine, proline, glutamate, creatine, dimethylarginine, and urea. For young organisms arginine is an essential amino acid for optimal growth and development, and must therefore be provided in the diet. For adults, arginine is a conditionally essential amino acid, especially in such conditions as trauma, burn injury, small-bowel resection, and renal failure. L-arginine administration improves cardiovascular, pulmonary, immune, and digestive functions and protect against the early stages of cancerogenesis.