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 Black Cohosh and Breast Cancer A Review of the Scientific Studies By James Meschino, DC, MS, ND Human observational studies (epidemiological studies) and experimental evidence suggest soy isoflavones, which act as phytoestrogens (plant-based estrogens) in the body, help reduce the risk of breast cancer. In Asia, where soy isoflavone intake is high, the incidence of breast cancer in women is 75 percent lower than in North America.1,2 Soy isoflavones have been shown to slow the cell division rate of breast cells, an effect associated with a lower risk of developing cancerous mutations.3The herb known as black cohosh also contains the isoflavone formononetin, which has been shown to act as a phytoestrogen in human studies.4 In Europe, black cohosh has been used with great success for the past 40 years as a treatment for menopausal symptoms, PMS and other female reproductive disorders in place of conventional hormone replacement therapy and oral contraceptives.5 Black cohosh also has been recommended in the United States for more than 100 years and was an official drug of the U.S. Pharmacopoeia from 1820 to 1926. This was the era prior to the political movement allowing pharmaceutical companies to dominate the market, in concert with their growing influence on the prescribing practices of medical practitioners. Over the years, many studies have documented black cohosh's effectiveness and safety. Published reports from Germany indicate it has a high safety profile and is associated with few and infrequent side effects, which include nausea, vomiting, headaches, dizziness, breast pain (mastalgia). No drug interactions are reported in the medical literature, adding to the evidence that it is a safe intervention for the management of menopausal symptoms, as well as PMS, dysmenorrhea and other female reproductive complaints.5,6 Throughout its documented use by millions of women, there has been no indication that supplementation with black cohosh increases risk of breast cancer or any other female reproductive cancer.7 Moreover, black cohosh has been shown to have a safety profile that is superior to that of hormone replacement therapy. HRT is known to increase the risk of breast cancer by 2.3 percent per year and has been shown to increase risk of other conditions (heart disease and stroke), according to the recently published results of the Women's Health Initiative Study.8,9 Intrigued by the physiological effects of black cohosh on female reproductive tissues, a number of researchers have designed experimental studies to examine the influence of black cohosh on breast cancer risk. As stated previously, its long historical use in Europe and the United States has shown that it is not associated with an increased risk of breast cancer, or any other cancer.10 Additionally, all of the experimental studies performed to date, involving the use of human breast cells and human breast cancer cells have shown that standardized extracts of black cohosh actually block the development of breast cancer and/or decrease the ability of breast cancer cells to divide and multiply. The assumption was that black cohosh might encourage the growth of breast cancer cells because it has a weak estrogenic effect, which is likely to promote proliferation of these cells. However, in vitro studies using human breast cells and human breast cancer cells have demonstrated the opposite effect. In these studies black cohosh has been shown to have an anti-proliferative effect on a number of human breast cancer cell lines. Bodinet and Freudenstein showed that black cohosh extract significantly inhibited human breast cancer cells (MCF-7 breast cancer cell line) from proliferating.11 They also showed that black cohosh extract enhanced the effectiveness of the breast cancer drug tamoxifen, in regard to its ability to suppress the proliferation of breast cancer cells. These researchers concluded that black cohosh extract may be a safe, natural remedy for menopausal symptoms in patients who have had breast cancer. Tamoxifen is given to patients who previously had estrogen-receptor-positive breast cancer to help prevent recurrence or spread. Experimental data suggest that black cohosh should be considered as a component of the treatment protocol when tamoxifen is administered. Extracts of black cohosh can be taken safely by patients who are susceptible to breast cancer (and possibly should be used as a means of chemoprevention [cancer prevention]).12 The study by Dixon-Shanies and Shaikh also demonstrated that black cohosh extract blocks the growth of human breast cancer cells (T-47D cell line). These researchers surmise that in-vitro studies suggest that certain herbs, such as black cohosh extract and soy (particularly the genistein isoflavone), may have potential in the prevention of breast cancer.13 As one in nine women in the U.S. develops breast cancer, some experts suggest that it may be prudent for women to use a well-designed black cohosh and soy isoflavone supplement as a preventive measure throughout adult life (unless contraindications are present). Theoretically, the anti-proliferative effects of these natural herbal agents acting on breast cells, would give the immune system a better chance to destroy cancer cells before they have an opportunity to thrive. A recent study funded by the Susan G. Komen for the Cure Foundation showed that a specific strain of mice (bred to be more susceptible to the development of spontaneous breast cancer) were no more likely than nonsupplemented mice to develop breast cancer during one full year of black cohosh supplementation.15 This study did show, however, that there was an increase in lung metastasis in mice in the black cohosh group (27 percent), compared to the non-supplemented mice (11 percent). Whether this is an incidental or significant finding needs to be confirmed by further studies. Studies suggest that black cohosh in humans does not increase breast cancer risk and may, in fact, reduce the risk of this disease. It may also provide additional protection against recurrence (while managing the hot flashes induced by the tamoxifen) in patients with a previous history of breast cancer.11-13 In fact, Freudenstein and Bodinet concluded that extracts of black cohosh can be taken safely by patients who are susceptible to breast cancer.12 Additionally, Burdette, et al., demonstrated that many natural ingredients within black cohosh extract inhibit free-radical damage (mutations) to the DNA of human breast cancer cells (S30 cancer cell line) upon exposure to a potent free-radical source (menadione).14 The results showed that many substances contained within black cohosh (methyl caffeate, caffeic acid, ferulic acid, cimiracemate A, fukinolic acid) exhibited powerful antioxidant effects. The standardized grade that demonstrates clinical efficacy involves the use of black cohosh extract providing 2.5 percent triterpene content. A usual daily dosage for women experiencing PMS and/or dysmenorrhea (painful menstruation) is 40 or 80 mg, twice per day.7 Active ingredients in black cohosh extract also exhibit anti-spasmodic effects upon smooth muscle, which may account for its ability to relieve menstrual cramps. The triterpene glycosides are also the only known precursor (building block) from which the body can increase synthesis of progesterone. This likely contributes to PMS management when corpus luteum failure, resulting in low secretions of progesterone, has been shown to be a contributing factor to PMS.16 Studies examining the toxicity of black cohosh, which have used high dosages of this herb in rats for long periods of time, suggest that black cohosh is very nontoxic and can be used long-term. Black cohosh should not be taken during pregnancy.17 References
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All Rights Reserved, Naturopathy Digest, 2011.
Date Last Modified - Friday, 17-Oct-2008 12:11:18 PDT
About the Author: Dr. James Meschino practices in Toronto, Ontario. He can be contacted via his Web site: 