Carnitine is naturally occurring compound that was discovered in muscle tissue back in 1905. The name carnitine is derived from the Latin carnis meaning flesh. Carnitine is widespread in nature and can be found in all organs of mammals and many lower forms of animals and also in many microorganisms and plants (Fraenkel and Friedmann, 1957). Its chemical structure was identified in the late 1920s as 3-hydroxy-4-N,N,N-trimethylaminobutyrate. The existence of two enantiomers was later discovered and the natural carnitine was found to be the L- form. There are several excellent reviews on the metabolism and function of carnitine (Robouche and Seim, 1998: Borum and Bennett, 1986).

Although carnitine is synthesized in our body, under certain physiologic conditions, the synthesis falls short of meeting the needs, and therefore carnitine is considered a "conditionally essential" and a "vitamin-like" nutrient. In this regard, it is similar to nutrients such as coenzyme Q10, choline and taurine. Carnitine is synthesized in the body from two amino acids, namely L-lysine and L-methionine. Although some refer to carnitine as an amino acid, it is not in the true sense of the word, nor is it a structural component of any protein.

There are primary and secondary deficiencies of carnitine. Among the various causes are genetic (primary), renal disease, liver disease, pure vegetarianism, diets deficient in certain vitamins and minerals, drug interactions (particularly anticonvulsant drugs), and aging.