Health Off The Shelf > Endeavors, Spring 2000

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UNC-CH Dept
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People's Pharmacy

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Researchers are excited about the possibility that genistein will become an effective anticancer agent. As an isoflavone, it’s one of three kinds of phyto-estrogens, or plant estrogens, and is actually similar in chemical structure to an estrogen our bodies make. It’s unique in that it can work as both an estrogen and an anti-estrogen. In postmenopausal women and in men with hormone-related cancers, genistein provides the body with needed estrogen to inhibit the signal from estrogen receptors that tell cancer cells to grow. In premenopausal women with breast cancer, genistein has the opposite effect by becoming an anti-estrogen as it competes with normal estrogen for binding to estrogen receptors on cells, which could decrease cancerous cell growth.

The only type of food containing a significant amount of the isoflavone genistein is soy. Another isoflavone found in soy is daidzein. While researchers are still studying the specific benefits of daidzein, they have decided that for the prostate cancer study they will use it in combination with genistein because they found that the combination is absorbed better and stays in the body longer.

Again with the cancer patients, researchers will be looking at safety and absorption rates. They want to see if these patients absorb genistein in the same way as healthy volunteers. Because previous animal and in vitro studies have shown genistein to slow the progression of prostate cancer, researchers have also decided to test prostate-specific antigen (PSA) levels at the beginning and end of the study. PSA levels give insight on how quickly the cancer is growing. While not a main objective of the study, the results should be a good indication of whether it’s worth pursuing a study that looks at genistein as a therapeutic agent for cancer as well as a preventive agent, Tyndall says.

If all goes well, it might take eight to ten years to complete the necessary series of three trials that test genistein for safety and efficacy, then compare it to other treatments that have already been approved by the FDA. That’s a long time for cancer patients to wait, and many aren’t willing, Tyndall says. “When I’ve spoken to prostate cancer support groups, I’ve talked with men who are taking up to 1,200 mg a day on their own. They’re buying genistein pills over the counter, and many are taking between five and ten pills a day,” she says.

When taken in quantities greater than found in food, consumers should be aware that supplements can become drug-like. “While many supplements may turn out to do something useful, people need to be cautious,” Zeisel says. “They need to weigh for themselves the risks because later on researchers might find serious side effects.”

The genistein used in the study is provided to NCI by Protein Technologies International.

How safe are medicinal herbs?

Medicinal herbs such as St. John’s wort, feverfew, and ginseng may be flying off the shelves, but are they really safe? That’s one of the questions top researchers in the field attempted to answer at the first international scientific conference on “The Efficacy and Safety of Medicinal Herbs,” held at UNC-CH March 2-3.

Speakers came from Canada, Germany, England, and the United States to discuss what’s been confirmed about eight of the world’s most widely used herbs. Unanimously, all of the speakers concluded more research is needed to understand the long-term effects of these herbs.

While most seem to be safe, one of the herbs discussed—comfrey, used as a laxative or anti-inflammatory medication—has been found to cause severe liver damage. Banned in Germany and Canada, this herb is still freely available in health food stores in the United States.

The researchers believe that medicinal herbs have great potential for preventing and treating illnesses but caution that until more research is conducted, consumers need to understand the consequences of self-medicating. Lenore Arab, professor of epidemiology and nutrition and cochair of the conference, says, “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.”

Because herbs are sold as food rather than as drugs, there are no set standards of quality for individual herbs. Varro Tyler, a well-known expert in the field from Purdue University, says, “There is absolutely no way that consumers can be assured that what is on the label is actually in the package, other than the reputation of the producer.”

The bottom line, Tyler says, is that consumers, manufacturers, and medical professionals need to use common sense when it comes to herbal medicine. While herbs do not need to be regulated as stringently as synthetic drugs, he says, “the FDA needs to adopt a reasonable policy toward herbal medicine, and the federal government must support meaningful research.”

Results of the conference will be published as a supplement to the journal Public Health Nutrition in Fall 2000.

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