L-Carnitine

L-carnitine is a derivative of the amino acid, lysine. Its name is derived from the fact that it was first isolated from meat (carnis) in 1905. Only the L-isomer of carnitine is biologically active. L-carnitine appeared to act as a vitamin in the mealworm (Tenebrio molitor) and was therefore termed vitamin BT. Vitamin BT, however, is actually a misnomer because humans and other higher organisms can synthesize L-carnitine (see Metabolism and Bioavailability). Under certain conditions, the demand for L-carnitine may exceed an individual's capacity to synthesize it, making it a conditionally essential micronutrient.