Some commonly used herbal treatments may further increase the risk of breast and uterine cancer for women already predisposed to those diseases.
That's the suggestion of a new animal study presented 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 gynaecological complaints - as well as saw palmetto and rhodiola rosea root can have such a strong estrogenic effect they could increase the risk of oestrogen-related cancers.
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Herbs show oestrogen activity
"Despite the fact that these are plants, we demonstrated considerable estrogenic activity - including the ability to bind to oestrogen receptors" in much the same way as natural oestrogen or oestrogen 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 oestrogenic 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 oestrogen levels, Eagon says women who want to limit oestrogen exposure should think twice before using these herbs.
"The activity is there, so if you are avoiding oestrogen for any reason, you should probably not use these herbs," Eagon says. This is especially true for women at risk for oestrogen-sensitive cancers, particularly in the breast and the uterus.
An important caution 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 Centre 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 oestrogen-related cancers.
"If a woman is avoiding hormone replacement therapy because she is concerned about exposure to oestrogen, then she should also avoid these herbs - at least until we can confirm or refute these findings in human studies," Dillard says.
Women at risk should avoid these herbs
The study was an animal experiment using rats that had their ovaries surgically removed. This, Eagon says, automatically deprived the rats of their natural oestrogen supply.
However, when these same rats were exposed to the various herbs in the study, Eagon reports, researchers could again document measurable levels of oestrogenic activity. Specifically, the oestrogen in the plants was able to bind to oestrogen receptors in the rats, acting much like a true hormone.
In one respect, the findings show these oestrogenic 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 oestrogen 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.
Previous studies confirm result
In previous studies, also conducted by Eagon, other herbs traditionally used for gynaecological complaints and menopause symptoms also demonstrated strong oestrogenic 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 oestrogen receptors in the lab, and to induce oestrogenic 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 oestrogen receptive positive tumour should definitely not use these herbs.
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