Creatine is a nitrogenous organic acid that occurs naturally in vertebrates and helps to supply energy to muscle. Creatine was identified in 1832 when Michel Eugène Chevreul discovered it as a component of skeletal muscle, which he later named creatine after the Greek word for flesh, Kreas. In humans and animals, approximately half of stored creatine originates from food (mainly from fresh meat). Since vegetables do not contain creatine, vegetarians show lower levels of muscle creatine which, upon creatine supplementation, rise to a level higher than in meat-eaters. In humans, about half of the daily creatine is biosynthesized from three different amino acids - arginine, glycine, and methionine. The rest is taken in by alimentary sources. Ninety-five percent of creatine is later stored in the skeletal muscles.