The growing number of Americans who are taking traditional herbal medications for heart problems are unaware of the dangers those treatments pose, a new report says.

"They may be safe," said Dr. Arshad Jahangir, a consultant cardiologist at the Mayo Clinic in Arizona, and author of a report in the Feb. 9 issue of the Journal of the American College of Cardiology. "But in the United States, where patients often take multiple medications, there is a potential for harm."

While up-to-date statistics aren't available, it appears that more than 15 million Americans are using herbal remedies and the number is growing, Jahangir said.

"Consumers of these products think they are not getting proper attention from their physicians," he said. "The typical hands-on communication between physician and patient is getting compromised, and they are seeking that type of relationship."

Popular herbal remedies such as St. John's wort "have been used traditionally in populations where there are no other medications to use," Jahangir said. But now multiple medications are common for older people, so "anyone taking herbal products needs to pay attention to the advice of their medical providers, and they often don't ask for that advice," he said.

Herbal medications can affect the activity of prescription drugs, dampening or enhancing their effects, Jahangir said. For example, St. John's wort, which is used for a number of conditions, including depression and sleep disturbances, has its major effect on the liver, which is involved in the metabolism of many drugs, especially those for heart disease, he said.

"If you take it on top of these medications, their activity will be reduced -- blood pressure medications, rhythm-controlling medications," Jahangir said. "Most important, it can have an effect for transplant patients, since it is immunosuppressive."

Other herbs can also be problematic.

Ginkgo biloba, which is supposed to sharpen the mind, increases bleeding risk in those taking the blood-thinner warfarin or aspirin, while garlic, which is believed to boost the immune system, can increase the chances of bleeding among those taking warfarin, the researchers noted.

Even grapefruit juice, recommended as an aid in weight-loss programs, has potential dangers, he noted. It interferes with enzymes that break down drugs in the digestive system, including the statins used to lower cholesterol levels and amiodarone (Cordarone), used to treat and prevent abnormal heart rhythms, Jahangir said.

"Anyone taking alternative medical and herbal products needs to bring it to the attention of their medical providers," Jahangir said. "Often they don't, and physicians don't actively seek that information."

There is no formal count of Americans taking such medications, said Dr. Wallace Sampson, clinical professor emeritus of medicine at Stanford University, and founder and editor emeritus of the Scientific Review of Alternative Medicine, a decided skeptic on the issue. The most-cited data come from a survey whose results were published in 1993. The best current estimate is that up to 30 percent of the U.S. population turn to herbal remedies and similar unapproved medications, Sampson noted.

There are periodic reports about the potential dangers of such remedies, Sampson added. "There are quite a number of them in the medical literature, targeted to different specialties," he said. "Cardiac ones are quite high on the list, also drugs that affect the immune system."

Most controlled studies of alternative medications have not shown benefit, "but when you do enough studies you get a few positive results and that keeps the field alive," Sampson said.

Negative results haven't killed the hope that herbal medications can help, he said: "It's a free country, and all you can do is educate and hope people learn."

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