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Does Black Cohosh Prevent Breast Cancer?
Abstract & Commentary
By Donald Brown, ND. Dr. Brown is Founder and Director, Natural Product Research Consultants, Inc; he serves on the Advisory Board of the American Botanical council and the President's Advisory Board, Bastyr University, Seattle, WA, and is an Advisor to the Office of Dietary Supplements at the National Institutes of Health; he is a consultant for Nature's Way, Inc.
Source: 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;120:1523-1528.
In a population-based, case-control study, women were asked about their use of "hormone-related" dietary supplements in an attempt to determine their association with risk of breast cancer. Participants included 949 breast cancer cases (mean age 63.0 years; 677 European American and 272 African American) and 1524 age-matched controls (mean age 61.8 years; 905 European American and 619 African American) from three counties of the Philadelphia metropolitan area. Women with ductal carcinoma in situ, lobular carcinoma in situ, and other nonmalignant tumor types were excluded. Controls could have no history of breast cancer.
Telephone interviews were used to collect information about the use of "hormone-related supplements" (HRS). Women were asked about the use of the following: Biest, black cohosh, Remifemin, DHEA, daidzein, dong quai, Estroven, genistein, ginseng, isoflavones, Promensil, red clover, Rejuvex, soy "medications," steroid creams, Triestrogen, and yam creams. Respondents could list up to five of these HRS used at least three times a week for one month or more any time before the reference date, which was defined as the date of diagnosis for the cases and the date of completion of the screening for the controls.
Use of HRS varied significantly by race, with African-American women being more likely than European-American women to use any herbal preparation (19.2% vs 14.7%, P = 0.003). Among the more commonly used preparations, African-American women were significantly more likely than European-American women to use black cohosh (5.4% vs 2.0%, P = 0.003), ginseng (12.5% vs 7.9%, P < 0.001), and red clover (4.7% vs 0.6%, P < 0.001). Use of other HRS (including Remifemin) was listed as being no more than 1% of women in the sample, with none reporting use of daidzein. Comparing women who took any HRS compared to those that did not, risk of breast cancer was significantly lower in the former (adjusted odds ratio 0.65, 95% CI: 0.49-0.87). Use of black cohosh had a significant breast cancer protective effect (adjusted OR 0.39, 95% CI: 0.22-0.70). This association was similar among women who reported either use of black cohosh or Remifemin (adjusted OR 0.47, 95% CI: 0.27-0.82). Although very preliminary, results suggested that the protective effect of black cohosh and/or Remifemin may be greater in the ER positive and PR positive groups compared to ER negative or PR negative tumors (these differences were small).
The answer to my somewhat provocative question in the title of this review is most likely "no." While surveys such as this suffer greatly by poor identification of supplements (eg, not listing black cohosh and Remifemin in one category), this study does suggest that black cohosh does not seem to increase the risk of cancer as was feared following a mouse study.1 It should also be noted that confounding factors, such as diet and physical activity, were not considered.
While data on the efficacy of black cohosh for vasomotor symptoms in menopausal women continue to be mixed, this large survey, coupled with previously reviewed safety data,2 suggest black cohosh is a safe herbal supplement that is unlikely to qualify as an "HRS" due to data failing to demonstrate hormonal effects for the root extract. It should also be noted that the study did not find any correlation between risk factor and any of the other "HRS" reported.
Although the supplements studied in this survey were poorly identified, the results suggest that black cohosh does not increase risk of breast cancer and may possibly decrease risk. Controlled studies with at-risk populations are needed to confirm these preliminary findings.
1. Davis V, et al. Effects of black cohosh in MMTV-neu transgenic mice. Proc Amer Acad Clin Res. 2003; 44:208.
2. Rau¨ K, et al. First-time proof of endometrial safety of the special black cohosh extract (Actaea or Cimicifuga racemosa extract) CR BNO 1055. Menopause. 2006;13: 678-691.