Mysterious Black Cohosh
Black cohosh is native to North America and for more than two centuries women have been using it to successfully relieve menstrual and menopausal discomfort. In modern times, both research and clinical practice have verified its effectiveness for reducing hot flashes and other symptoms during the perimenopausal years and beyond. But even after 50 years of scientific investigation, randomized double blind trials, in vitro, in vivo, population studies and various forms of poking, prodding and dissecting, we still do not understand the mechanisms of action of Cimicifuga racemosa, aka black cohosh.1 Some herbs do not readily give up their secrets.
Although the physiology of hot flashes has been studied for more than 30 years, it is still not known exactly why or how they occur. Estrogen is definitely involved—because if it wasn’t, then estrogen therapy would not relieve vasomotor symptoms as well as it does—but that’s not the whole story. For example, researchers have found no differences in estrogen levels in women who have hot flash symptoms and those who don’t. Because black cohosh root extract relieves hot flashes effectively, producing results similar to estrogen replacement therapy, it is commonly thought of as a phytoestrogen, but this is not a fair assumption. Herbs are often misunderstood and often pigeon-holed for ease of understanding their application and then much gets lost in the translation. I myself have been guilty of describing black cohosh as a “phytoestrogen”, because it eases the symptoms caused by low estrogen. But unlike the isoflavones in soy, alfalfa or red clover, which are simpler to define by their chemical components and mechanism of action as phytoestrogens, how black cohosh root exerts its influence is still a mystery. Truly, the best way to think about some herbs for reproductive health is that they usually enable what is most appropriate to occur but do so in ways we simply don’t understand clearly.
For example, a study in 20062 compared the effects of black cohosh to conjugated estrogens on bone turnover. Both had positive results. However, analysis of bone turnover markers indicated that while estrogen inhibited osteoclast activity, black cohosh stimulated osteoblast activity. These are two different actions, resulting in a similar outcome—bone protection.
In addition, more than one retrospective study looked at the relationship between use of supplements and breast cancer risk. Population studies suggest that taking black cohosh does not significantly increase breast cancer risk. In some studies, the use of black cohosh had a significant protective effect against breast cancer and might prolong disease-free survival in patients with breast cancer.3,4 A study published in the journal Nutrition and Cancer in 2007 investigated specifically whether black cohosh extract exerted estrogenic influence on the breast, concluding that black cohosh “relieved menopausal symptoms without systemic or breast specific estrogenic effects“.5 Research shows that black cohosh doesn’t seem to affect estrogen receptors. These reports on the estrogenic activity of black cohosh extract are “consistent with the effects of a selective estrogen receptor modulator (SERM), which acts as an estrogen agonist in some tissues and as an estrogen antagonist in others. The ideal SERM is one which acts as an estrogen on bone and brain, but does not act as an estrogen in the breast and uterus. BCE (black cohosh extract) may contain compounds which fit the criteria of a SERM.”6
So the long and the short of what we know is that black cohosh has estrogen-like effects that are exerted by still unknown mechanisms. Research suggests that extracts of black cohosh do not bind to estrogen receptors, up-regulate estrogen-dependent genes or stimulate the growth of estrogen-dependent tumors in experimental animals. The general consensus and conclusion seems to be that black cohosh safely helps provide the hormone balancing that is desired by many women to help them ease through the menopausal transition.
Lisa Murray, RDN, LD
Lisa is a Licensed Dietitian/Nutritionist and Medical Educator for Emerson Ecologics. Herbalist, nutrition counselor, writer and educator, Lisa’s passion is teaching others how to integrate botanicals and nutrition supplements into a healthy diet and lifestyle, for optimal health and healing.
- Henneicke-von Zepelin, HH. 60 years of Cimicifuga racemosa medicinal products. Wien Med Wochenschr (2017) pp1-13. doi:10.1007/s10354-016-0537-z
- 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. 2006 Mar-Apr;13(2):185-96. PMID: 16645532 DOI: 10.1097/01.gme.0000174470.44822.57
- Henneicke-von Zepelin HH, Meden H, Kostev K, Schröder-Bernhardi D, Stammwitz U, Becher H. Isopropanolic black cohosh extract and recurrence-free survival after breast cancer. Int J Clin Pharmacol Ther. 2007 Mar;45(3):143-54.
- Fritz H, et al. Black cohosh and breast cancer: a systematic review. Integr Cancer Ther. 2014 Jan;13(1):12-29. doi: 10.1177/1534735413477191. Epub 2013 Feb 25.
- Ruhlen RL. Black cohosh does not exert an estrogenic effect on the breast. Nutr Cancer. 2007;59(2):269-77. PMID: 18001221 DOI: 10.1080/01635580701506968
- Ruhlen RL,Sun G,Sauter,E. Black Cohosh: Insights into its Mechanism(s) of Action. Integr Med Insights. 2008; 3: 21–32. Published online August 27, 2008.