L-carnitine is a vitamin-like nutrient, related in chemical structure to the B vitamins. In the human body, L-carnitine is synthesized from the amino acid lysine in the liver and kidneys. Dietary sources of L-carnitine include meat and dairy products, with red meat being the richest source. L-carnitine supplements are produced synthetically.
In the body, L-carnitine plays a crucial role in the transport and metabolism of fatty acids, helping the muscles utilize fat as an energy source. Supplemental L-carnitine is popular for improving energy levels in athletes and fatigue sufferers and for promoting cardiovascular function.
L-carnitine supplements are typically taken in doses ranging from 1 to 4 grams per day. It is generally well tolerated in this dosage range, with no significant side effects reported in human clinical studies. There is no known toxicity with L-carnitine, even at very high doses.