Black Cohosh and Breast Cancer Risk

Many menopausal women seek relief from symptoms like hot flashes, heart palpitations, mood swings, and sleepless nights. For some, this search leads to hormone-related supplements (HRSs) – many of which contain phytoestrogens, plant-derived hormones that are chemically similar to the human estrogens in decline during menopause.

But can the use of these supplements make a difference – good or bad – in a woman’s likelihood of developing breast cancer, which is also largely regulated by estrogen?

No change in risk seen in most supplements

A study conducted by a team from the University of Pennsylvania Center for Clinical Epidemiology and Biostatistics* looked at 949 breast cancer patients and 1,524 women who had never had the disease. The women, all from the Philadelphia area, were either Caucasian or African-American.

On a one-time questionnaire, each woman was asked to list up to five of the following HRSs she had used at least three times a week for at least one month prior to her diagnosis (for the breast cancer patients) or prior to the date she was screened for study participation (for the women without cancer):

Black cohosh
Dong quai
Red clover
Soy medications
Steroid creams
Yam creams

In addition to taking thorough medical, reproductive, family and lifestyle histories, researchers also collected comprehensive demographic data from each woman.

Fifteen of the17 supplements revealed no significant relationship to breast cancer risk one way or the other. However, black cohosh, a perennial herb native to North America, as well as Remifemin, an herbal preparation derived from black cohosh, did yield some interesting data.
Black cohosh: “We do believe there’s an effect”

The research team estimates that the women who reported using black cohosh and/or Remifemin had a 61 percent lower risk of developing breast cancer than the women who did not use either of these supplements, says principal investigator Timothy R. Rebbeck, PhD.

It’s important, however, to keep two things in mind: There was no way of knowing exactly how much black cohosh and/or Remifemin the women used – or for how long they used it.

“Although they’re usually pretty mild, these herbal preparations typically have no standard labeling, regulation, dosage recommendations, or even information about what other compounds are in them,” says Rebbeck.

And because the women were asked simply whether or not they had used any of the HRSs for at least four weeks, a response of yes could mean that a woman could have used a small amount of an HRS for three months – or a large amount for ten years. In fact, the active ingredient in black cohosh hasn’t even been positively identified.

Therefore, “the results are significant but one should be aware of the error associated with the exposure measurement,” says Rebbeck, adding that he knows of no meaningful toxicities associated with any of the HRSs investigated in the study.

Although the data showed no differences in breast cancer risk between the Caucasian and African-American study participants – perhaps because the sample size was too small – African-Americans were significantly more likely to have used HRSs.

 “We do believe that black cohosh has an effect on reducing breast cancer risk, but our data don’t give us a good estimate of the magnitude of this effect,” Rebbeck says.

Because there is still so much to be understood about HRSs, he cautions women against relying on any herbal preparation as their sole means of breast cancer prevention.

“One of the dangers is that people sometimes think, ‘I’m taking cohosh, so I don’t have to do anything else,’” he says. “But not doing the other things – like getting regular mammography screenings – is what can hurt you. Herbal preparations are at best additions – not alternatives – to standard prevention methods.”

As always, people should speak with their doctors before taking any herbal preparations or supplements.

“Our current cancer-prevention tools are pretty good, and some of them do work, but we need to spend more time thinking about creative ways of preventing cancer and giving people options,” Rebbeck says. “These ways might include alternative medicines that may be less toxic than some of what’s out there now.”

“Maybe there’s something in these herbal compounds that could be a valuable addition to our cancer prevention medicine chest, but we need to do many more studies before we know what this something is.”

* Rebbeck, TR, et al., A Retrospective Case-Control Study of the Use of Hormone-Related Supplements and Association with Breast Cancer. Int J Cancer, 2007 Apr 1; 120(7):1523-8.

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