Though unlikely to burn fat, L-carnitine shows promise
L-carnitine got its name from the Latin word for meat (caro), in which the vitamin-like compound was first identified. Few people are deficient in the compound (in addition to being made in the body, L-carnitine is abundant in meat and dairy products), but it is essential, playing a critical role in converting fat to energy. Animal studies suggesting that supplemental L-carnitine could burn fat and make old rats act younger made it popular as a supplement.
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ses: Over-the-counter L-carnitine supplements are most often taken by people seeking to improve exercise performance, increase lean muscle mass and improve energy levels, heart health and memory. Prescription L-carnitine is used to treat L-carnitine deficiency caused by genetics, kidney and heart disease or chemotherapy.
Dose: Doses effective in clinical trials ranged from 500 milligrams to 3 grams a day. Propionyl-L-carnitine, the form of L-carnitine that has shown the most promise in managing heart disease, is not sold over the counter.
Precautions: L-carnitine supplements can cause headaches, nausea, cramps, diarrhea and flu-like symptoms. They may increase the risk of seizures in susceptible people.
Research: Overall, studies in humans suggest that the supplement doesn’t help to improve endurance, burn fat, build muscle, treat Alzheimer’s disease or improve memory. But in studies of people with end-stage renal disease or heart failure, one form of the supplement, propionyl-L-carnitine, improved energy levels and heart and lung function during exercise. Preliminary results from an ongoing, large-scale Italian trial suggest L-carnitine improves heart health after a heart attack. A U.S.-based clinical trial is investigating whether 2 grams a day can reverse fatigue in L-carnitine-deficient cancer patients.
-- Elena Conis
Dietary supplement makers are not required by the U.S. government to demonstrate that their products are safe or effective. Ask your healthcare provider for advice on selecting a brand.
