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Black cohosh is a tall perennial herb originally found in the northeastern United States. Native Americans used it primarily for women's health problems, but also as a treatment for arthritis, fatigue, and snakebite. European colonists rapidly adopted the herb for similar uses. In the late nineteenth century, black cohosh was the principal ingredient in the wildly popular Lydia E. Pinkham's Vegetable Compound for menstrual cramps.
What Is the Scientific Evidence for Black Cohosh?
The body of evidence regarding black cohosh for menopausal symptoms remains incomplete and inconsistent. 1 The best study was a 12-week, double-blind, placebo-controlled trial of 304 women with menopausal symptoms. 2 This study appeared to find that black cohosh was more effective than placebo. The best evidence was for a reduction in hot flashes. However, the statistical procedures used in the study were somewhat unusual and open to question.
Promising results were also seen in a 3-month, double-blind study of 120 menopausal women. 3 Participants were given either black cohosh or fluoxetine (Prozac). Over the course of the trial, black cohosh proved more effective than fluoxetine for hot flashes, but fluoxetine was more effective than black cohosh for menopause-related mood changes.
Previous smaller studies have found improvements not only in hot flashes but also in other symptoms of menopause. For example, in a double-blind, placebo-controlled study, 97 menopausal women received black cohosh, estrogen, or placebo for 3 months. 4 The results indicated that the herb reduced overall menopausal symptoms (such as hot flashes) to the same extent as the drug. In addition, microscopic analysis showed that black cohosh had an estrogen-like effect on the cells of the vagina. This is a positive result because it suggests that black cohosh might reduce vaginal thinning. However, black cohosh did not affect the cells of the uterus in an estrogen-like manner; this too is a positive result, as estrogen’s effects on the uterus are potentially harmful. Finally, the study found hints that black cohosh might help protect bone. However, a great many of the study participants dropped out, making the results less than reliable.
One study, too small to have reliable results from a statistical point of view, found black cohosh equally effective as 0.6 mg daily of conjugated estrogens. 5 A study reported in 2006 found that black cohosh has weak estrogen-like effects on vaginal cells and possible positive effects on bone (specifically, stimulating new bone formation). 6 An earlier study also found multiple benefits with black cohosh, but its results are difficult to trust. This trial followed 80 women for 12 weeks and compared the effects of black cohosh, estrogen, and placebo. 7 Again, black cohosh improved menopausal symptoms and vaginal cell health. However, in this study estrogen proved less effective than placebo. This result is so difficult to believe that it casts serious doubt on the meaningfulness of the results.
Several other studies are also often cited as evidence that black cohosh is useful for various symptoms of menopause, but in reality they prove nothing at all. 8 These trials lacked a placebo group. Although women reported improvements in symptoms, there is no way to know whether black cohosh was responsible. Women given placebo reliably report improvements in menopausal symptoms too; a 50% reduction in hot flashes is fairly typical. 9 Thus, it is possible that the benefits seen in these studies had nothing to do with black cohosh.
A substantial (244-participant) double-blind study published in 2007 compared black cohosh against the synthetic hormone tibolone, and found them equally effective for treating menopausal symptoms. 10 Though not approved as a drug in the US, tibolone does appear to be effective for menopausal symptoms, therefore these results are somewhat promising. 11 However, this study lacked a placebo group, and since the placebo effect is powerful for this condition, this omission significantly reduces the meaningfulness of the result.
One interesting double-blind study evaluated a combination therapy containing black cohosh and St. John's wort in 301 women with general menopausal symptoms as well as depression. 12 The results showed that use of the combination treatment was significantly more effective than placebo for both problems.
A smaller study using a combination of the same two herbs found improvements in overall menopausal symptoms as well as cholesterol profile. 13 In contrast, several other studies failed to find benefit. For example, in a 12-month, double-blind, placebo-controlled study of 350 women, participants were given either black cohosh, a multibotanical containing 10 herbs, the multibotanical plus soy, standard hormone replacement therapy, or placebo. 14 The results showed that hormone replacement therapy was more effective than placebo, but the other treatments were not. In addition, a double-blind study of 122 women failed to find statistically significant benefits with black cohosh as compared to placebo, 15 as did another study enrolling 132 women, 16 as well as one that involved 124 women using a black cohosh/soy isoflavone combination. 17 These negative outcomes were possibly due to the relatively small sizes of the black cohosh groups. In a condition such as menopausal symptoms, where the placebo effect is strong, and when the treatment is relatively weak, large numbers of participants are necessary to show benefit above and beyond the placebo effect. Nonetheless, this is an impressive number of negative studies, and some question must remain about the efficacy of this herb.
The bottom line: Black cohosh may be modestly effective for reducing hot flashes and other symptoms of menopause, but doubts remain.
Some interesting information has developed regarding how black cohosh may work. In the past, the herb was described as a phytoestrogen, a plant-based chemical with estrogen-like effects. However, subsequent evidence indicates that black cohosh is not a general phytoestrogen, but may act like estrogen in only a few parts of the body: the brain (reducing hot flashes) and bone (potentially helping to prevent or treat osteoporosis), and, perhaps to some extent, in the vagina. 18 It does not appear to act like estrogen in the breast or the uterus. 19 If this theory is true, black cohosh is a selective-estrogen receptor modifier (SERM) somewhat like the drug raloxifen (Evista). However, more evidence is needed to establish the facts of the matter.
Because of it estrogenic properties, researchers investigated whether black cohosh might be helpful in women who were having difficulty conceiving. Women with unexplained infertility who were not responding clomiphene, a commonly used medication to induce ovulation, were randomly divided into two groups. Both groups continued to receive clomiphene, but the women in one of the groups also received 120 mg of black cohosh. Pregnancy rates were significantly higher in the black cohosh plus clomiphene group compared to the clomiphene only group. 20
Breast Cancer Survivors
Women who have had treatment for breast cancer frequently experience hot flashes, often but not always due to the use of the estrogen-antagonist medications like tamoxifen . Estrogen treatment is not an option for this problem, as it might increase risk of cancer recurrence. Because black cohosh does not seem to have estrogen-like actions in the breast, researchers felt safe to try it in 85 women who had undergone treatment for breast cancer. 21 Unfortunately, the results were not encouraging: in this 2-month, double-blind, placebo-controlled trial, black cohosh did not reduce hot-flash symptoms.
The most commonly used dosage of black cohosh is 1 or 2, 20-mg tablets twice daily of a standardized extract, manufactured to contain 1 mg of 27-deoxyactein per tablet.
Note:An analysis of 11 available black cohosh products found that 3 of them contained an Asian herb related to black cohosh rather than the proper herb. 22 Make sure not to confuse black cohosh with the toxic herb blue cohosh (Caulophyllum thalictroides).
- Kanadys WM, Bozena LG, Jan O. Efficacy and safety of Black cohosh ( Actaea/Cimicifuga racemosa ) in the treatment of vasomotor symptoms--review of clinical trials] Ginekol Pol. 2008;79:287-96.
- Osmers R, Friede M, Liske E, Schnitker J, Freudenstein J, Henneicke-von Zepelin HH. Efficacy and safety of isopropanolic black cohosh extract for climacteric symptoms. Obstet Gynecol. 105(5 Pt 1):1074-83.
- Oktem M, Eroglu D, Karahan HB, Taskintuna N, Kuscu E, Zeyneloglu HB. Black cohosh and fluoxetine in the treatment of postmenopausal symptoms: a prospective, randomized trial. Adv Ther. 24(2):448-61.
- Wuttke W, Seidlová-Wuttke D, Gorkow C. The Cimicifuga preparation BNO 1055 vs. conjugated estrogens in a double-blind placebo-controlled study: effects on menopause symptoms and bone markers. Maturitas. 44 Suppl 1():S67-77.
- Wuttke W, Raus K, Gorkow C. Efficacy and tolerability of the Black cohosh (Actaea racemosa) ethanolic extract BNO 1055 on climacteric complaints: A double-blind, placebo- and conjugated estrogens-controlled study. Maturitas. 2006 Aug 21. [Epub ahead of print]
- Wuttke W, Gorkow C, Seidlová-Wuttke D. Effects of black cohosh (Cimicifuga racemosa) on bone turnover, vaginal mucosa, and various blood parameters in postmenopausal women: a double-blind, placebo-controlled, and conjugated estrogens-controlled study. Menopause. 13(2):185-96.
- Stoll W. Phytotherapeutic agent affects atrophic vaginal epithelium. Double-blind study: Cimicifuga vs. an estrogen preparation [translated from German]. Therapeutikon. 1987;1:23-31.
- Schulz V, Hansel R, Tyler VE. Rational Phytotherapy: A Physicians' Guide to Herbal Medicine. 3rd ed. Berlin, Germany: Springer-Verlag; 1998:246.
- MacLennan A, Lester S, Moore V. Oral estrogen replacement therapy versus placebo for hot flushes: a systematic review. Climacteric. 4(1):58-74.
- Bai W, Henneicke-von Zepelin HH, Wang S, Zheng S, Liu J, Zhang Z, Geng L, Hu L, Jiao C, Liske E. Efficacy and tolerability of a medicinal product containing an isopropanolic black cohosh extract in Chinese women with menopausal symptoms: a randomized, double blind, parallel-controlled study versus tibolone. Maturitas. 58(1):31-41.
- Swanson SG, Drosman S, Helmond FA, Stathopoulos VM. Tibolone for the treatment of moderate to severe vasomotor symptoms and genital atrophy in postmenopausal women: a multicenter, randomized, double-blind, placebo-controlled study. Menopause. 13(6):917-25.
- Uebelhack R, Blohmer JU, Graubaum HJ, Busch R, Gruenwald J, Wernecke KD. Black cohosh and St. John's wort for climacteric complaints: a randomized trial. Obstet Gynecol. 107(2 Pt 1):247-55.
- Chung DJ, Kim HY, Park KH, et al. Black Cohosh and St. John's wort (GYNO-Plus®) for climacteric symptoms. Yonsei Med J. 2007;48:289-294.
- Newton K, Reed S, Grothaus L, et al.. The Herbal Alternatives for Menopause (HALT) Study: background and study design. Maturitas. 2005;16:134-146.
- Frei-Kleiner S, Schaffner W, Rahlfs VW, Bodmer Ch, Birkhäuser M. Cimicifuga racemosa dried ethanolic extract in menopausal disorders: a double-blind placebo-controlled clinical trial. Maturitas. 51(4):397-404.
- Pockaj BA, Gallagher JG, Loprinzi CL, Stella PJ, Barton DL, Sloan JA, Lavasseur BI, Rao RM, Fitch TR, Rowland KM, Novotny PJ, Flynn PJ, Richelson E, Fauq AH. Phase III double-blind, randomized, placebo-controlled crossover trial of black cohosh in the management of hot flashes: NCCTG Trial N01CC1. J Clin Oncol. 24(18):2836-41.
- Verhoeven MO, van der Mooren MJ, van de Weijer PH, Verdegem PJ, van der Burgt LM, Kenemans P, CuraTrial Research Group. Effect of a combination of isoflavones and Actaea racemosa Linnaeus on climacteric symptoms in healthy symptomatic perimenopausal women: a 12-week randomized, placebo-controlled, double-blind study. Menopause. 12(4):412-20.
- Liske E, Hanggi W, Henneicke-Von Zepelin HH, et al. Physiological investigation of a unique extract of black cohosh ( Cimicifugae racemosae rhizoma ): a 6-month clinical study demonstrates no systemic estrogenic effect. J Womens Health Gend Based Med. 2002;11:163-174.
- Reed SD, Newton KM, LaCroix AZ, Grothaus LC, Grieco VS, Ehrlich K. Vaginal, endometrial, and reproductive hormone findings: randomized, placebo-controlled trial of black cohosh, multibotanical herbs, and dietary soy for vasomotor symptoms: the Herbal Alternatives for Menopause (HALT) Study. Menopause. 15(1):51-8.
- Shahin AY, Ismail AM, Zahran KM, Makhlouf AM. Adding phytoestrogens to clomiphene induction in unexplained infertility patients--a randomized trial. Reprod Biomed Online. 16(4):580-8.
- Jacobson JS, Troxel AB, Evans J, Klaus L, Vahdat L, Kinne D, Lo KM, Moore A, Rosenman PJ, Kaufman EL, Neugut AI, Grann VR. Randomized trial of black cohosh for the treatment of hot flashes among women with a history of breast cancer. J Clin Oncol. 19(10):2739-45.
- Jiang B, Kronenberg F, Nuntanakorn P, Qiu MH, Kennelly EJ. Evaluation of the botanical authenticity and phytochemical profile of black cohosh products by high-performance liquid chromatography with selected ion monitoring liquid chromatography-mass spectrometry. J Agric Food Chem. 54(9):3242-53.