News Release

Scientists: herb known as comfrey can ruin liver, other herbs appear helpful

Peer-Reviewed Publication

University of North Carolina at Chapel Hill

CHAPEL HILL -- Comfrey, an herb widely available in U.S. health food stores and sometimes used as a laxative or anti-inflammatory medication, can cause severe liver damage and should be banned, according to scientists speaking Thursday (March 2) at the University of North Carolina at Chapel Hill. Pyrrolizidine alkaloids present in the plant have been linked to poisoning after people consumed them in tea and contaminated cereals.

"Therapeutic approaches include avoiding intake of comfrey and, once severe liver damage has emerged, liver transplantation," said Dr. Felix Stickel of the University of Erlangen and Salem Medical Center in Heidelberg, Germany. "Taking this into consideration, it is difficult to understand why comfrey is banned in Germany and Canada but is still freely available in the United States."

Mechanisms by which comfrey can ruin the liver are unclear, but the main injury appears to be destruction of small veins leading to cirrhosis and eventually liver failure, he said. Patients may display either acute or chronic symptoms, including abdominal pain, high blood pressure in the organ's portal vein and liver enlargement.

Stickel was one of the presenters at the first international scientific conference on "The Efficacy and Safety of Medicinal Herbs," sponsored by UNC-CH's Institute of Nutrition and schools of public health and medicine and other organizations. Speakers from Canada, England, Germany and the United States discussed what's been confirmed about eight of the world's most widely used herbs -- garlic, ginseng, Ginko biloba, comfrey, saw palmetto, feverfew, echinacea and St. John's wort.

"It's essential that health professionals know what we know about these products and what's still speculation, so that they can give informed advice," said Dr. Lenore Arab, professor of epidemiology and nutrition at UNC-CH. "Right now, the public has stopped asking, and even if people were asking, most health professionals do not feel that they are in a position to give advice. As a result, the train is running wild down the track. People are self-medicating without any guidance. They might be taking extremely high, possibly dangerous doses because they think more is better, or they may be getting so little that they're simply wasting their money."

Arab, along with doctoral student Aaron Fleischauer and Dr. Harunobo Amangase of Wakunaga of America Co., Ltd. of Mission Viejo, Cal., discussed garlic, which, in both its raw and cooked forms, appears to protect somewhat against colorectal and stomach cancers, they said. Supplements and over-cooked garlic may be much less effective. The herb also exhibits an ability to lower fats in the blood, reduce clotting, promote circulation, protect the liver and enhance the immune system.

"Eating a clove a day has a measurable effect and might therefore be a good idea," Arab said.

Dr. Pierre LeBars of New York University's psychiatry department described how researchers have demonstrated the effectiveness of a Ginko biloba extract in treating dementia in at least two large randomized clinical trials. Compared with patients who received inactive compounds, those who took the extract tended to have either a slower decline in mental function or small improvements.

"However, the role that this specialized extract of Ginko biloba can play as an alternative or an adjunct agent for the treatment of dementia needs to be delineated by control studies clarifying the dose-response relationship and detecting potential changes in the course of disease," LeBars said.

People have used ginseng for millennia in the Far East as a tonic and medicine, but identifying its active components remains a major challenge, said Dr. David E. Kitts of the University of British Columbia, whose research has shown the herb may be a good antioxidant.

"We have identified a potentially important role for ginseng in enhancing our abilities to manage oxidative stress," Kitts said. "However, we are no further ahead at determining (whether ginseng's ability) is due to a specific component or represents a synergistic action by a mixture of phytochemicals."

Dr. Edzard Ernst of England's University of Exeter conducted five independent searches of the world's medical literature and reviewed the most rigorous studies of feverfew as a method of preventing migraine headaches. Although most favored feverfew over inactive compounds and few side effects were found, the clinical effectiveness of the herb in preventing such headaches was not proven.

Other studies suggested that saw palmetto improved urologic symptoms among men with benignly enlarged prostate glands, according to Dr. Timothy J. Wilt of the Minneapolis Veterans Administration Center for Chronic Diseases. Echinacea, which leads U.S. dietary supplement sales, may help prevent colds or make them less severe, but should not be taken for systemic illnesses or if allergy appears, said Dr. Rudolf Bauer of Germany's Heinrich Heine University in Dusseldorf.

Dr. P. Murali Doraiswamy, a Duke University psychiatrist, said St. John's wort is the most promising herb being studied for depression and that nearly half of the patients he has treated already have tried it on their own, but often irregularly or at incorrect doses.

"I believe the jury is still out on whether St. John's wort is as effective as prescription antidepressant treatments," he said. "Clinical depression is a major public health problem,... and there are about 35,000 suicides a year. Hence, I recommend that anyone with persistent symptoms of low mood or loss of interest see a health practitioner rather than self-medicate themselves."

Other organizations sponsoring or helping with the event include the Sarah W. Stedman Center for Nutritional Studies at Duke University Medical Center, the National Institute of Environmental Health Sciences' National Toxicology Program, the American Society for Nutritional Sciences, the National Institute on Aging, East Carolina University School of Medicine and CABI Publishing in Wallingford, U.K. A book summarizing the presentations will be published later this year.

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Note: Arab can be reached at (919) 966-7450 or via e-mail at LenoreA@unc.edu for more information. Contact: David Williamson, (919) 962-8596.


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