The amino acid L-carnitine is a cofactor that is required for the metabolism of fats and their subsequent transport into the mitochondria, where they undergo oxidation and produce energy.* L-carnitine is probably best known for its cardiac benefits.* In the heart muscle, L-carnitine facilitates fatty acid use, and promotes rhythm, myocardial blood flow, and cardiac output.* It has also been shown to benefit athletic performance.* For example, studies show improvements in running speed, increased maximal oxygen uptake, and decreases in average oxygen consumption, heart rate, and lactic acid.* L-carnitine has been shown to help maintain normal levels of total cholesterol, LDL cholesterol, lipoprotein(a) (associated with LDL cholesterol), and triglycerides.* It also promotes healthy sperm count and sperm motility.*In addition to supporting athletic performance, cardiac function, healthy lipid levels, and reproductive health, L-carnitine has also been shown to promote general wellbeing, appetite control, and carbohydrate metabolism.* Individuals prone to being deficient in L-carnitine or for whom supplementation would be advisable, include those on dialysis or who are HIV-positive.*