American College of Physicians: Internal Medicine — Doctors for Adults ®


What you need to know about herbal supplements

By Ingrid Palmer

PHILADELPHIA—If you're wondering how to work with patients taking botanical supplements like echinacea and ginseng, you're not alone. Speakers at an Annual Session presentation, "Herbal Medicine: What Works and What Doesn't," said that the number of patients taking supplements—and the number of substances available to the public—continues to grow, creating confusion among physicians.

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From 1990 to 1998, the use of botanical supplements to treat illness in the United States increased 380%. Studies indicate that 42% of Americans tried some type of alternative therapy in 1998 and that 17% used herbal supplements on a regular basis. It is estimated that by 2010, annual sales of herbal products in the United States will total approximately $25 billion, according to studies published by the University of Illinois at Chicago/National Institutes of Health Center for Botanical Dietary Supplements Research.

Fredi Kronenberg, PhD, director of Columbia University's Richard & Hinda Rosenthal Center for Complementary & Alternative Medicine, said that while some substances on the market have been shown to be effective in clinical trials, "the jury is still out on a number of supplements." As a result, she said, physicians need to keep up with the data and talk to their patients.

Norman R. Farnsworth, PhD, a research professor of pharmacognosy at the University of Illinois, suggested the following approach when trying to determine which botanical products are safe and effective:

  • Make sure the manufacturer has been in business for five years or more.

  • Choose products that use a single botanical species, as they are more likely to have been tested. (None of the compound botanical component mixtures have been tested.)

  • Be sure the product's label conforms to FDA regulations, which state that dietary supplement labels must include the product name, Latin name of the plant, part of the plant that is used, amount in each dose, a claim or statement of nutritional support and an FDA disclaimer.

  • Choose extracts over powdered plant material. (Effects of powdered material have not been studied in humans.)

  • Avoid any supplement that sounds too good to be true. If the label uses the words "cure" or "miracle," you can assume that the product's claims are bogus.

During the presentation, Dr. Kronenberg and two other speakers—Gail B. Mahady, PhD, a researcher at the University of Illinois at Chicago, and Adriane Fugh-Berman, MD, assistant clinical professor, department of health care sciences, George Washington University—summarized the effects of some of the more commonly used botanical supplements. The following information is based on clinical studies of popular herbs:

  • Soy. This supplement is widely used to reduce cholesterol, to improve cardiovascular health and occasionally to treat hot flashes in menopausal women. The FDA has approved claims that using soy can improve cardiovascular health and reduce cholesterol, but other claims have not been confirmed.

  • Echinacea. This popular plant, indigenous to the United States, is used to stimulate the immune system and treat minor skin problems and wounds. Findings from more than 50 clinical trials have shown that echinacea can help boost the immune system and decrease the duration of some illnesses, as long as the supplement is taken when symptoms first appear and is used for one to two weeks. There are no known drug interactions, but reactions may occur in patients who are allergic to plants in the daisy family. Dosing guidelines for echinacea are difficult to determine.

  • Kava. While kava is a ceremonial drink in Polynesia, it is used in the United States to treat anxiety and stress. Clinical trials have found that kava helps reduce anxiety, but possible side effects include gastrointestinal discomfort, headache, dizziness and skin reactions. Chronic use may cause yellowing of skin, rashes and eye irritation. There may be possible negative interactions with other drugs such as alcohol.

  • Black cohosh. This herb, native to North America, is used to treat menopausal symptoms such as hot flashes and moodiness. Data suggest the substance is beneficial when used for up to six months, but no long-term studies have been conducted. There are no known side effects.

  • St. John's Wort. Clinical studies have shown that St. John's Wort effectively treats mild to moderate depression. It may produce negative interactions with antidepressants and other drugs such as warfarin, phenprocoumon and cyclosporine.

  • Korean ginseng. One of the top 10 best-selling botanicals in the United States, Korean ginseng is used to treat erectile dysfunction and as an antioxidant and immune stimulant. Studies suggest that the substance can help improve mood and physical function, but Dr. Mahady noted that the research methodologies of those trials were relatively poor. Korean ginseng can interact with warfarin and phenelzine. Because of a lack of safety data, women who are pregnant or lactating are advised to avoid using the herb.

  • Gingko biloba. This substance is commonly used to treat memory impairment due to age, as well as Alzheimer's disease and vertigo. Clinical studies have shown gingko biloba can help improve symptoms of memory loss. The substance, however, can interact with warfarin. And because the product may inhibit the blood's ability to clot, side effects can include lung hemorrhaging or bleeding in areas with fragile blood vessels such as the gums.

  • Goldenseal. Commonly used to treat gastric complaints and diarrhea, goldenseal is currently No. 8 on the list of top-selling botanicals in the United States. Despite its popularity, Dr. Mahady said that "there is no clinical evidence to support the use of goldenseal whatsoever." Because no studies have been conducted on the herb, she recommended not using it.

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