Herbal Remedies Pose Danger for Heart Patients

Some popular herbal supplements, including St. John's wort and ginkgo biloba, may be wreaking havoc on people who take heart medications.

Mayo Clinic researchers say that supplements interact with drugs for high blood pressure, high cholesterol, blooding clotting, and irregular heart beat.

Ginkgo, St. John's wort, and even garlic can either diminish the effectiveness of medicines or increase potency, which can lead to internal bleeding. The findings are published in the Journal of the American College of Cardiology.

More than 15 million Americans use herbal remedies or high-dose vitamins, says researcher Arshad Jahangir, a Mayo Clinic professor of medicine and consultant cardiologist in Arizona. Ginkgo, sold by companies like Nature's Way Products, has almost $100 million in annual sales, according to industry estimates. Jahangir says doctors don't routinely ask whether their patients are using these herbal remedies.

"Many people have a false sense of security about these herbal products because they are seen as natural," Jahangir says. "But natural doesn't always mean they are safe. Every compound we consume has some effect on the body, which is, in essence, why people are taking these products to begin with."

Ginkgo, often taken to improve circulation or improve memory, can increase the risk of bleeding in patients taking the anticlotting drug warfarin or aspirin, according to the researchers. Garlic, which is taken to help immunity, also can increase bleeding when taken with warfarin, they add.

St. John's wort, used for years to treat depression and sleep disorder, reduces effectiveness in drugs that treat irregular heartbeat and high blood pressure, researchers say.

Jahangir doesn't completely pooh-pooh the use of supplements: They have been used for hundreds of years. But he says they should be studied to test their effect on people taking medications. Herbal remedies aren't classified as drugs by the U.S. government and, therefore, the oversight is a bit more lax.

"These herbs have been used for centuries—well before today's cardiovascular medications—and while they may have beneficial effects, these need to be studied scientifically to better define their usefulness and, more importantly, identify their potential for harm when taken with medications that have proven benefit for patients with cardiovascular diseases," he says.