The herb black cohosh (Cimicifuga racemosa or Acteae racemosa) reduces mammary tumor development in a rat model of breast cancer, according to a new study. Black cohosh is used for a variety of menstrual problems and to treat menopausal symptoms such as hot flashes. To conduct the study, female Sprague-Dawley rats were treated with an extract of black cohosh. The rats were divided into groups that received various doses of black cohosh extract for 40 weeks starting at 56 weeks of age: Group I received 35.7 mg; Group II received 7.14 mg; and Group III received 0.714 mg per kg body weight. A control group of rats was left untreated. A carcinogen was used to induce mammary tumors in the rats and the incidence of benign and malignant mammary tumors was measured at the end of the study.

A dose-dependent reduction in the incidence of malignant mammary tumors was observed in Group I and Group II compared to Group III rats (who received the lowest dose). In addition, black cohosh treatment reduced Ki-67 (a measure of proliferation) and cell cycle regulating gene (cyclin D1, which is important for cell cycle progression) expression in benign mammary tumors. The authors conclude that black cohosh may have chemopreventive potential for mammary cancer.

Black cohosh appears to be safe for breast cancer survivors

While more study would be required to establish a chemopreventive role for black cohosh root, it appears to be safe for breast cancer survivors. Preliminary evidence suggests that it is not particularly estrogenic, and while there have been isolated reports of liver damage, larger studies have not found this problem. Studies that have attempted to determine whether black cohosh can reduce hot flashes have yielded mixed results, suggesting that black cohosh could be helpful for some women (and useless for others).

We caution against using herbal mixtures with multiple ingredients to treat hot flashes and other menopausal symptoms. The preparations sold in the U.S. are essentially unregulated. Even if the preparations contain exactly the herbs on the label, some other herbs used for menopause or sexual problems are very estrogenic and have been found to increase breast cancer risk.