L-Carnitine is an amino acid that acts as a vitamin-like compound, responsible for the transport of long-chain fatty acids into the energy producing mitochondria inside cells. Since the carrier molecule for fatty acids, acyl-CoA, cannot penetrate the cell membrane of the mitochondria without carnitine, a deficiency in carnitine results in decreased fatty acid concentrations in the mitochondria, and as a result, reduced energy production.
L-Carnitine is only found in animal food sources such as meat, poultry, and dairy products. It can be made in the human body, although premature infants and some adults do not make sufficient amounts.
L-Carnitine is a popular supplement for heart health, liver health, and weight loss. Studies generally use dosages ranging from 2 or more grams per day.