Bottom Line: There is still no conclusive evidence that black cohosh is effective for menopausal symptoms.
It is not clear if black cohosh is beneficial for menopausal symptoms due to conflicting results from various studies. There is not enough evidence to support its anticancer effects in humans. Although black cohosh is generally safe, a few cases of liver failure have been reported from its use.
Menopausal symptoms Most studies on black cohosh have been done in Europe using the German product Remifemin®.
A recent study in Poland compared low (39 mg/day) and high (127 mg/day) dose Remifemin® in 149 menopausal and postmenopausal women with moderate to severe symptoms. After twelve weeks, the low dose was just as effective as the high dose in relieving menopausal symptoms and depression. In addition, this product appeared not to have an estrogenic effect, since it did not stimulate vaginal cell growth or change the women's blood levels of female sex hormones. Studies of longer duration may be helpful.
In another study of menopausal symptoms, 60 healthy women were divided into three groups. Group 1 received 40 drops twice a day of black cohosh (Remifemin®); Group 2 received 2 mg of diazepam (Valium®) daily; and Group 3 received hormone replacement therapy (HRT). Symptom reduction in the three groups was similar. After three months the black cohosh group showed a significant decrease of menopausal symptoms.
The manufacturer of Remifemin® conducted a trial of 152 women with a moderate degree of menopausal symptoms. One group received black cohosh (Remifemin®) two tablets twice a day and the other group received 1 tablet twice a day. In both groups menopausal symptoms improved significantly by the same amount. However, this trial lacks a true control group (receiving a placebo pill) with which to compare the effects seen with Remifemin®.
After twelve weeks in a randomized controlled study of 80 menopausal women, those taking black cohosh extract (Remifemin®) experienced notable improvements in symptoms compared to women taking either hormone replacement therapy (HRT) or a placebo pill. The number of hot flashes dropped from an average of 5 daily to 3.5 in the estrogen group and to less than 1 in the black cohosh group. These results suggest that Remifemin® may be even more effective than HRT in reducing menopause symptoms, but this study did not follow the women long-term to determine if Remifemin® is safer than HRT.
Hot flashes from breast cancer treatment A randomized, controlled trial studied the effect of black cohosh on hot flashes in women who had finished breast cancer treatment. Forty-two women received black cohosh and 43 received a placebo pill twice a day for 2 months. Fifty-nine women were receiving treatment with tamoxifen as well. The black cohosh and placebo groups reported similar improvements in symptoms, although women taking black cohosh had a greater decrease in sweating. From these data alone, it cannot be determined whether black cohosh is an effective treatment of hot flashes. In addition, this study did not follow patients long-term to determine whether black cohosh is safe in estrogen receptor-positive (ER+) breast cancer patients.
Another randomized, controlled trial also studied the effect of black cohosh on hot flashes in premenopausal women who had finished breast cancer treatment and were undergoing tamoxifen therapy. 46 patients received tamoxifen and 90 women received tamoxifen as well as black cohosh for twelve months. Comparing the two groups, the researchers found that significantly more women receiving black cohosh were free of hot flashes and that women receiving black cohosh had significantly fewer severe hot flashes than those on tamoxifen alone.
This product is regulated by the F.D.A. as a dietary supplement. Unlike approved drugs, supplements are not required to be manufactured under specific standardized conditions. This product may not contain the labeled amount or may be contaminated. In addition, it may not have been tested for safety or effectiveness.
Black cohosh should not be confused with blue cohosh.
Precaution: It is still quite controversial whether or not black cohosh possesses estrogenic activity. This product should be used under the supervision of a physician.
You currently have, or have been treated for, an estrogen receptor-positive (ER+) cancer (It is still unclear whether black cohosh acts in the same manner as estrogen, and might therefore stimulate growth of these tumors).
You are taking hormonal medications such as birth control pills (If black cohosh has estrogen-like activity, it will interfere with these medicines).
Because it is still unclear whether black cohosh has estrogenic effects, women with estrogen receptor-positive (ER+) cancers should avoid this supplement.
Obtained from root of the plant, black cohosh is used as a dietary supplement to relieve the symptoms of menopause and dysmenorrhea. Black cohosh alone (1)(2)(3) or in combination with other herbs (4), (5) has been shown in clinical studies to be effective in the treatment of menopausal symptoms, but other studies show conflicting conclusions (6)(31). Studies evaluating black cohosh to treat hot flashes from breast cancer treatment also yielded mixed results (10)(11)(12). Black cohosh has antiosteoporotic effects (8) and has been shown to enhance bone formation (9). In vitro studies show black cohosh decreases prostate cancer cell proliferation (14) and induces an apoptotic response in liver cells (21). However, it also increased the incidence of metastatic disease in mice (16). Black cohosh increases disease-free survival in breast cancer patients(15). Whether black cohosh has estrogenic activity is debatable. Patients with hormone-sensitive diseases should use black cohosh with caution. Black cohosh may inhibit CYP3A4 (17) and can interact with medications that are substrates of this enzyme. Several cases of hepatic failure have been reported from use of black cohosh(18)(19)(20). Black cohosh was shown to increase the toxicity of chemotherapy drugs, including doxorubicin and docetaxel in vitro (13).
Black cohosh may have estrogenic effects, but there are conflicting data (23). Studies also showed that it has no effect on LH, FSH, prolactin, or estradiol (24). A black cohosh extract was shown to have antiproliferative and antiestrogenic effects in ER-negative cells. This suggests that black cohosh mediates its effects via an estrogen-independent pathway (25), possibly through Her2 signaling (26) It is unknown whether or not it has a cardiovascular effect. Black cohosh increases the incidence of metastatic disease in mice (16).
Black cohosh should not be confused with blue cohosh.
Precaution: It is still quite controversial whether or not black cohosh possesses estrogenic activity. This product should be used under the supervision of a physician.
After reviewing 30 independent cases of reported hepatoxicity associated with black cohosh intake, the United States Pharmacopeia's Botanical Expert Committee decided that black cohosh products should include a statement of caution concerning their use (28).
(Oral): Gastrointestinal upset and rashes are most common followed by dizziness, headaches, nausea, and vomiting when higher than normal doses are taken (27)
Reported (Oral): Hepatotoxicity has been reported following use of black cohosh (18)(20).
Tamoxifen: Black cohosh may have an additive antiproliferative effect. Chemotherapy drugs: Black cohosh may increase the toxicity of doxorubicin and docetaxel (13). Cytochrome P450 3A4: Black cohosh may interact with drugs that are metabolized by CYP3A4 enzyme (17).
Pockaj BA, et al. Phase III double-blind, randomized, placebo-controlled crossover trial of black cohosh in the management of hot flashes: NCCTG trial N01CC. J Clin Oncol 2006;24:2836-41. One hundred and thirty-two women with persistent hot flashes for at least one month were randomized to receive 20mg of black cohosh extract twice a day or placebo for four weeks. This was followed by a crossover period of four more weeks where women who initially received black cohosh were given placebo and vice versa. Participants maintained weekly diaries of symptoms including nausea, excessive sweating, chills, headache, nervousness etc. At the end of the study period, women who received black cohosh reported a 20% reduction in the hot flash score compared to a 27% decrease by women on placebo. These data suggest that black cohosh is not superior to placebo in reducing hot flashes.
Jacobson JS, et al. Randomized trial of black cohosh for the treatment of hot flashes among women with a history of breast cancer. J Clin Oncol 2001;19:2739-45. A prospective, randomized, double-blind evaluation of black cohosh extract on hot flashes in women who had completed primary breast cancer treatment. Patients were stratified based on concurrent tamoxifen treatment and instructed to take 1 tablet of black cohosh (n=42) or placebo (n=43) twice daily for 2 months. Primary outcome measured was change in frequency and intensity of hot flashes. Serum levels of follicle stimulating hormone (FSH) and luteinizing hormone (LH) were also measured. Patients receiving black cohosh did have a statistically significant decrease in sweating, but all other symptom improvements were similar between treatment groups. No significant increases in FSH or LH were noted. Of the adverse events reported, none were attributed to black cohosh. Additional studies are required to assess the safety of black cohosh in patients with breast cancer.
