By the way, doctor: Ginkgo biloba: What's the verdict?

Q: A friend recently recommended that I take the herb ginkgo biloba to protect against getting dementia. Is it effective, and is it safe?

A: The first thing you should consider is that the FDA doesn't regulate the manufacture of any herbal remedy, so the purity and potency of the ginkgo biloba you buy hasn't been checked.

Studies looking at the potential health benefits of ginkgo have shown conflicting results. Some research suggests that it may slow the progression of Alzheimer's disease and dementia caused by multiple strokes. Ginkgo may improve leg pain caused by atherosclerosis of arteries in the legs and speed recovery after a stroke. Positive results have been reported for ringing in the ears (tinnitus), vertigo, and even attacks of pain from hemorrhoids. Yet there are also studies that conclude that ginkgo doesn't have beneficial effects on these various conditions. In short, the results are mixed.

What about risks? Some people are allergic to ginkgo, which is more likely if you react to poison ivy or poison oak easily.

A more serious potential problem is an increased risk of bleeding, particularly if you're taking a medicine that "thins the blood," such as aspirin, warfarin (Coumadin), or clopidogrel (Plavix). Taking ginkgo with certain other herbal remedies, such as garlic (Allium sativum), or vitamins (particularly vitamin E) poses the same problem. In addition, there's some evidence that ginkgo may increase the frequency of seizures in people who have epilepsy and could cause dangerously low blood sugar levels in people taking sugar-lowering medications or the herb bitter melon (Momordica charantia).

Ginkgo has been used by millions of people over thousands of years. Many people must have believed that they benefited from it, and told their friends. In my view, that means we should be studying ginkgo with the same rigor that we study pharmaceutical drugs — not dismissing it because it's an "alternative medicine." It takes time and many studies before a consensus emerges on the benefits and risks of any treatment. For ginkgo, that time has not yet arrived.

— Anthony L. Komaroff, M.D.
Harvard Health Letter Editor in Chief

To learn the evidence behind the benefits and safety profiles of various vitamins and minerals, buy the Harvard Special Health Report Making Sense of Vitamins and Minerals: Choosing the foods and nutrients you need to stay healthy.

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