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5 Risky Herbal Supplements

Even though they're natural, some herbal supplements can be dangerous.
By Sonya Collins
WebMD Feature
Reviewed by Laura J. Martin, MD

"All natural" -- it's on the labels of a growing number of foods, cosmetics, cleaning products, and over-the-counter remedies. This is, in part, what makes herbal medicine so popular. But does natural always mean safe?

Herbal medicine is the use of plants as medicine. Typically taken by mouth or applied to the skin, medicinal herbs can come in several forms, such as ointments, oils, capsules, tablets, and teas.

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Though many people may use them as medicine, herbal supplements are not regulated by the FDA like prescription and over-the-counter drugs are.  For this reason, some potentially dangerous herbs may be available in stores, online, and even in local coffee shops. You take them at your own risk. Before taking any herb, be sure to research it and talk to your health care providers -- doctors, pharmacists, and anyone else who's involved in your medical care.

Risky Herbs

"Some people think herbal supplements really work but that they are harmless," but if it acts like a drug in the body, then it can also have a negative effect, says Adriane Fugh-Berman, MD, an expert on medicinal herbs and dietary supplements and a professor at Georgetown University School of Medicine. 

"Most herbs we use in the U.S. are pretty benign," Fugh-Berman says, "but some are dangerous and others are if not taken correctly."

Anything that works like a drug is going to have some risks, says Cydney McQueen, PharmD, a professor at the University of Missouri-Kansas City School of Pharmacy.

For herbs that pose major risks, the most common risks are liver and kidney damage and drug interactions.

Here are examples of herbs that carry risks you may not know about. This is not a complete list of every potentially risky herb or other supplement; it simply shows that some very risky substances are available to anyone over the counter. So again, be sure to talk to your health care providers before taking any herbs.

St. John's Wort

St. John's wort (Hypericum perforatum) can ease mild to moderate depression, says Andrew Weil, MD, who is the founder and director of the Arizona Center for Integrative Medicine at the University of Arizona. But there is not enough evidence that it helps with major depression.

Besides, depression isn't something to treat without help. "It's not the common cold. If someone wants to use St. John's wort for depression, they still must be managed by a health care provider," McQueen tells WebMD.

Here's one major reason why: drug interactions. St. John's wort can make many other drugs less effective. There have been cases of unintended pregnancies in women taking St. John's wort and birth control pills and cases of organ rejection in those taking St John's wort with anti-rejection drugs after a transplant.

"If you are taking any prescription drug and are interested in trying a course of St. John's wort for mild to moderate depression, first discuss possible interactions with your doctor or pharmacist," says Weil, whose line of dietary supplements includes a product containing St. John's wort.

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