That's the suggestion of a new animal study presented today at the annual meeting of the American Association for Cancer Research in San Francisco. Researchers from the University of Pittsburgh Cancer Institute offer new evidence that herbs such as red clover and motherwort -- traditionally used for gynecological complaints -- as well as saw palmetto and rhodiola rosea root can have such a strong estrogenic effect they could increase the risk of estrogen-related cancers.
"Despite the fact that these are plants, we demonstrated considerable estrogenic activity -- including the ability to bind to estrogen receptors" in much the same way as natural estrogen or estrogen replacement does, says study author Patricia Eagon, an associate professor of medicine at the University of Pittsburgh.In addition, Eagon found that extracts of maca root, cramp bark and turmeric root also exhibited modest estrogenic activity.
While all the plants can successfully be used to ease a wide variety of symptoms, particularly those associated with menopause and the corresponding drop in natural estrogen levels, Eagon says women who want to limit estrogen exposure should think twice before using these herbs.
"The activity is there, so if you are avoiding estrogen for any reason, you should probably not use these herbs," Eagon says. This is especially true for women at risk for estrogen-sensitive cancers, particularly in the breast and the uterus.
For alternative medicine expert Dr. James Dillard, the findings are an important caution. He adds, though, that they should be viewed in the proper perspective.
"First, what holds true for rats doesn't always true for humans, so you can't make that automatic leap from an animal study to human application," says Dillard, clinical medical advisor at the Rosenthal Center of Alternative and Complementary Medicine at Columbia University.
That said, he also suggests women should err on the side of caution and approach the use of these herbs judiciously, particularly if they are at risk for any estrogen-related cancers.
"If a woman is avoiding hormone replacement therapy because she is concerned about exposure to estrogen, then she should also avoid these herbs -- at least until we can confirm or refute these findings in human studies," Dillard says.
The study was an animal experiment using rats that had their ovaries surgically removed. This, Eagon says, automatically deprived the rats of their natural estrogen supply.
However, when these same rats were exposed to the various herbs in the study, Eagon reports, researchers could again document measurable levels of estrogenic activity. Specifically, the estrogen in the plants was able to bind to estrogen receptors in the rats, acting much like a true hormone.
In one respect, the findings show these estrogenic botanicals may have strong clinical applications, such as the ability to reduce some menopause-related symptoms. However, "it might be wise to avoid these herbs in conditions where estrogen is contraindicated," Eagon says.
This would include women with a strong family history of breast or uterine cancer, or those who may have already had one or more bouts with either disease, she says.
In previous studies, also conducted by Eagon, other herbs traditionally used for gynecological complaints and menopause symptoms also demonstrated strong estrogenic activity. The herbs included dang qui root, black and blue cohosh, vitex berry, hops flower, wild yam and licorice root.
"All were shown to interact with the estrogen receptors in the lab, and to induce estrogenic responses in rats who had their ovaries removed," Eagon says.
For Dillard, both the old and new data imply that women who have a known estrogen receptive positive tumor should definitely not use these herbs.
What To Do: For more information on non-traditional treatments, check out the National Center for Complementary and Alternative Medicine. To learn more about estrogen receptive cancers, visit the Science Behind the News.