The amino acid L-carnitine is well known for its key role in the burning of fats. Specifically, L-carnitine transports fatty acids to the innermost section of the mitochondria (the cellular powerplants for energy) where they are used to create adenosine triphosphate (ATP), the energy currency of the body. Studies have shown that carnitine deficiency lowers ATP levels in various tissues. Carnitine deficiency also increases the susceptibility to fatigue from, and decreased the rate of recovery following, strenuous physical activity. Acetyl L-Carnitine (ACL) is the acetyl ester of the amino acid L-carnitine, which transports fats into the mitochondria. In the mitochondria these fats are converted to an energy source. It is a nutrient and naturally occurring metabolite that is involved in lipid, carbohydrate and protein, metabolism.