L-Arginine is a naturally occurring amino acid found in many foods. It plays an important role in the building of protein, which helps the body repair and grow muscle. It also helps in the formation of nitric oxide, which helps to open blood vessels. L-arginine also stimulates the body to produce insulin and growth hormone, as well as other chemicals. This article reviews about what is L-arginine, its advantages, side-effects and applications of L-arginine supplements.