Whether you run to lose weight, beat your personal best or just for the sheer love of the sport, supplements that promise to make you faster, better and stronger can be tempting. Too often, those promises are empty -- carnitine is one of those cases. Although it has shown promise in the treatment of several diseases, the hype surrounding its use is overblown.
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Your body makes its own carnitine in the kidneys and liver, and stores it in various muscles and organs for later use. Some hereditary conditions and diseases can cause this mechanism to falter, resulting in a carnitine deficiency that requires supplementation. You can get it naturally in the foods you eat, especially red meat, dairy foods, fish poultry and wheat, or you can take a supplement in the form of L-carnitine. Research into whether carnitine can provide effective treatment for diseases like peripheral vascular disease, kidney disease and male infertility is ongoing, but many people are familiar with carnitine as a performance or weight-loss aid.
Proponents claim that carnitine helps your body burn fat for energy, saving your glycogen stores for later in the workout. Theoretically, this would help you play harder, longer, because instead of calling on your glycogen stores right away, you would keep it in reserve for when your energy would normally start to flag. This myth has been debunked several times. A 1996 double-blind study in the "European Journal of Applied Physiology and Occupational Physiology" showed that carnitine did not enhance performance, affect the participants' metabolisms or help their exercise recovery in any way.
Maintaining a healthy body weight is important to your performance as a runner. Weight from muscle mass works for you, as it translates into increased power, but fat weight is dead weight and only slows you down. Carnitine has been used to stimulate weight loss by encouraging the body to burn fat for energy, but research has not proven this. The University of Maryland Medical center says that it may, however, help reduce fatigue, increase muscle mass and reduce overall fat mass, all of which can contribute to weight loss.
Because there is no evidence that supports the use of carnitine for weight loss or sports performance, there is no recommended dose for those uses. Follow the directions on the supplement you choose. Don't choose a D-carnitine supplement, because the UMMC suggests that it may disrupt your body's natural carnitine production and may produce side effects. Consult your doctor before taking carnitine, especially if you have kidney disease, hypertension, cirrhosis, diabetes or peripheral vascular disease, or are taking any medication.