Your kidneys and liver convert two amino acids, lysine and methionine, into a substance called l-carnitine, also known as caritine, that's needed by all your cells to turn fatty nutrients into energy. Healthy adults and children usually produce enough of this compound for the body's needs. But research suggests that taking extra l-carnitine could help keep you healthy and promote your overall well-being.
L-carnitine is an antioxidant compound that could protect your cells from long-term damage caused by free radicals -- chemicals produced in your cells as byproducts of digestion, in your skin when you're in sunlight or when you're exposed to environmental toxins, such as cigarette smoke. Over time, free radicals can damage cellular membranes and DNA, raising your risk of chronic diseases such as cancer. Laboratory research into l-carnitine has found that its antioxidant properties could protect you from a type of free radical-induced damage called oxidative stress. For example, a study published in February 2006 in the "International Journal of Cardiology" found that the cells which line your blood vessels produce substances that protect against free radicals when they're exposed to l-carnitine. Studies are still needed to identify the possible benefits of this effect, however.
Information summarized by experts at the Linus Pauling Institute suggests that taking carnitine might help slow the natural aging process. Cellular components that produce energy, called mitochondria, need carnitine for their biochemical reactions; the institute says that both mitochondrial function and levels of carnitine in your cells decline as you age. A number of laboratory studies have found that supplementing aging laboratory animals with a type of carnitine called acetyl-L-carnitine increased carnitine levels in their body tissues and improved energy production by their mitochondria. In one study, published in February 2002 in the "Proceedings of the National Academy of Sciences," older animals fed carnitine performed memory tasks better than a placebo group, but this possible anti-aging benefit still needs confirmation in clinical studies with human subjects.
Effects on Athletic Performance
The institute also reports that taking extra carnitine might improve your exercise tolerance and athletic performance through its potential ability to boost energy production. Some research has been conducted to test this possibility, including a study published in the February 2002 issue of the "American Journal of Physiology -- Endocrinology and Metabolism," which found that a small group of male subjects who took carnitine for three weeks and then did strenuous exercise had less muscle disruption than a placebo group. According to the institute, some other studies fail to support a benefit of carnitine for exercise performance, but these have been small, of short duration or not well-controlled, so larger clinical trials are still needed to determine conclusively whether taking extra carnitine boosts athletic performance.
Sources and Cautions
Although no minimum recommended amount of l-carnitine has been determined, many common foods are good sources. For example, beef provides 50 to 160 milligrams per 4-ounce serving, depending on the cut, while whole milk contains 8 milligrams per cup and 2 ounces of cheddar cheese provides 2 milligrams. Other foods, such as whole-wheat bread and asparagus, also contain small amounts. L-carnitine is available as a supplement from health food stores, but avoid d-carnitine supplements because they can interfere with L-carnitine. L-carnitine could interact with certain prescription medicines and might cause mild side effects, such as diarrhea. Talk to your doctor about l-carnitine before taking supplements to decide if they might help you.