Harvard Heart Letter

Heart Beat: Play it safe, avoid L-arginine supplements

Heart Beat

Play it safe, avoid L-arginine supplements

L-arginine, touted as a supplement that prevents and treats heart and circulation problems, doesn't help heart attack survivors — and it may even harm them.

L-arginine provides the raw material from which the body makes nitric oxide, a tiny, transient molecule that helps relax and open blood vessels. Johns Hopkins researchers put it to the test in a rigorous, two-year clinical trial of 153 heart attack survivors. Neither the volunteers nor their doctors knew who was taking three grams of the amino acid three times a day and who was taking a placebo. After just six months the researchers stopped the trial when a peek at the data showed six deaths among volunteers assigned to L-arginine compared with none in the placebo group. In a report in the January 4, 2006, Journal of the American Medical Association, they noted that L-arginine didn't reduce artery stiffness or improve the pumping power of the heart's left ventricle.

The six deaths in the L-arginine group could have happened by chance, or because of the L-arginine supplements. Until other work delineates the benefits and risks of this supplement, be wary of taking L-arginine pills.

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