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Is Garlic Good for Your Heart? A Review of the Evidence

NEW YORK (Jul 21, 2000)

Since at least 1500 B.C., people have believed in the health benefits of garlic. China and India used it as a blood-thinning agent, and it has been found in tombs in Egypt and Rome. There is evidence that athletes in the original Olympic Games used it. Garlic may have been one of the first sanctioned "performance-enhancing agents."

Whole books have been devoted to garlic (Allium sativum), and now two researchers at Weill Medical College of Cornell University have reviewed the evidence of garlic's benefits for the cardiovascular system from a scientific point of view, summarizing their findings in an article, "Garlic and Cardiovascular Disease," in the new issue (May-June) of the journal Nutrition in Clinical Care. The authors, Dr. Richard S. Rivlin, Chief of the Division of Nutrition, and Michelle H. Loy, see "growing evidence for a potential role of garlic derivatives together with other measures in the prevention of cardiovascular disease."

"Most of the scientific evidence to date," Loy and Rivlin write, has shown that "treatment with allium derivatives from garlic decreases levels of total serum cholesterol and LDL-cholesterol ['bad cholesterol'] with little effect on levels of HDL-cholesterol ['good cholesterol']."

This general result was not confirmed by every study reviewed by the authors, and they say that questions remain to be answered on exactly how and in what form garlic works. Allium compounds from garlic have been shown to inhibit cholesterol synthesis. Garlic supplements with the distinctive odor of garlic removed still retain efficacy.

"In addition to reducing serum lipids," Loy and Rivlin write, "there is evidence that garlic may also slow the atherosclerosis process and lower blood pressure." This, too, is borne out by a number of studies.

Other trials show that garlic may have anti-clotting activity, may have antioxidant effects, and may reduce homocysteine levels—all likely benefits for the cardiovascular system.

Because garlic is a food and not a licensed medication, it cannot be marketed as a product intended to diagnose, treat, or prevent any illnesses. However, it clearly has a very low toxicity—"a conclusion supported even by the studies that lack demonstration of a positive effect," the authors note. They conclude that while the mechanisms of action of garlic derivatives "require further clarification," garlic—together with other healthy dietary and lifestyle measures—may safely be recommended to people seeking a heart-healthy diet.