Black cohosh is probably best known as the herbal remedy for all things to do with women’s health. It has been used throughout the various stages of womanhood from painful periods to childbirth to the menopause.
Native to the Appalachian mountain region of North America, there are significant concerns about conservation of this plant species due to overexploitation.
Is black cohosh a victim of its own success or just another herb whose medicinal properties are misrepresented and over-marketed?
What Is Black Cohosh?
Black Cohosh (Actaea racemosa) is a perennial herb native to North America. Black cohosh was initially called Cimicufuga racemosa but has since been reclassified as an Actaea species. (I am not sure if that is an upgrade or downgrade but apparently botanists can spend hours having such debates). It is part of the butter cup family. It is also known as baneberry, black snakeroot, rattleweed, bug root, rheumatism weed, and bugbane.
Plants of this genus have been used in indigenous medicine in China, Japan, Europe, and North America for centuries. In North America, underground stems (dried rhizomes and roots) of black cohosh were used by both native American healers and the early colonists for the common problem of those times such as rheumatic complaints, headache, toothache, sore throat, menstrual cramps, cervical dilatation in childbirth, menopause, snakebite and as a vermifuge (vermifuge is a wonderful word use by parasitologists to describe anything that is used to expel worms).
Black cohosh was part of the United States Pharmacopeia from 1820 to 1936. To date, a total of 457 bioactive compounds have been identified in black cohosh. The key bio-actives identified so far include triterpenoid glycosides, phenylpropanoids, nitrogenous compounds, chromones, flavonoids and 4α-methyl steroid
There is an important distinction to be made between blue and black cohosh. Blue Cohosh (Caulophyllum thalictroides) was used in traditional medicine as a ‘partus preparators’ (something that prepares the woman for childbirth). However blue cohosh contains potentially dangerous compounds including caulosaponin and has been associated with a wide range of serious adverse (sometimes fatal) effects in both mother and baby. Black cohosh is different to blue cohosh, but both agents have been used together to aid labor.
The recommended dose of black cohosh extract is 40-160 mg per day, usually taken in two divided doses.
Black cohosh is sold as a teas, roots, extracts, tinctures an capsules. There are 395 black cohosh products for sale on Amazon. Black cohosh can cost up to $5 per fluid ounce.
Is There Any Research?
There are 803 publications on black cohosh including 61 clinical trials. There are 78 publications on blue cohosh but no human clinical trials.
Does It Help Sleep?
Technically, there are two studies looking at the effects of black cohosh on sleep. In reality, only one study is available to us for review as the second study shows an error message when trying to read the study details.
Chinese investigators published the results of a randomized, double-blind and placebo-controlled study which took place over a 6-month period. The study was done in forty-eight postmenopausal women aged 45-60 with sleep complaints. The women were randomized to either placebo or black cohosh.
Compared with placebo, black cohosh treatment led to significant polysomnographic changes, including increased sleep efficiency and decreased wake after sleep onset duration (1).
There is only one study looking at sleep and black cohosh. This study was limited to menopausal women which makes it difficult to extrapolate this study results to other patient demographics.
Does It Treat Diabetes?
There are no clinical trials looking at black cohosh in diabetes.
One study showed that isoferulic acid from back cohosh helps lower plasma glucose in diabetic rats (2). Similarly, another study showed that extract of black cohosh improved glucose and insulin sensitivity in diabetic mice (3).
There is no human based science to support a role for back cohosh in diabetes.
Does It Help Treat PCOS?
There is only one study looking at back cohosh in polycystic ovarian syndrome (PCOS). Egyptian researchers studied patients (194 study subjects) under the age of 35 years, presenting with infertility and PCOS. The women were randomised to either clomiphene or clomiphene plus black cohosh.
The study found that adding black cohosh to clomiphene-induction cycles with timed intercourse in polycystic ovarian syndrome improves cycle outcomes and pregnancy rates (4).
A single study shows the combination of black cohosh plus clomiphene improved pregnancy rates in women under the age of 35 with PCOS.
Does It Reduce Anxiety?
In traditional medicine, back cohosh is used for ‘melancholy’.
Only one clinical study looked at black cohosh for anxiety (5). Researchers from the University of Pennsylvania conducted a randomized, double-blind, placebo-controlled, parallel group trial of the efficacy and tolerability of black cohosh extract for the treatment of anxiety disorder due to menopause.
Women were were randomized to therapy with either pharmaceutical-grade black cohosh extract (15 subjects) or placebo (13 subjects) for up to 12 weeks.
No statistically significant anxiolytic effect of black cohosh (vs placebo). The authors defend the negative outcome by reminding us that the sample size was small and that the choice of black cohosh preparation, and dosage used may have been limiting factors producing negative results. Agreed, but then why design a study with limitations in the first place? Sometimes we just have to be gracious in defeat.
There is no evidence to suggest that black cohosh has anti-anxiety effects.
Does It Help With Osteoporosis?
There are no clinical trials looking at black cohosh for osteoporosis.
There is nothing to recommend black cohosh in the prevention or treatment of osteoporosis.
Does Black Cohosh Reduce Hot Flashes?
The literature on this is fascinating.
We start with a 2012 Cochrane review by Leach and colleagues. Using the accepted rigorous Cochrane methodologies and standards, the team evaluated 16 randomised controlled trials recruiting 2027 peri menopausal or post-menopausal women (8) . (Just to be clear, I am super sympathetic to Cochrane reviewers. These reviews are usually done by passionate researchers in their spare time and take an inordinate amount of time).
No significant difference was noted between black cohosh or placebo for hot flushes (p>0.79) or in the menopausal symptom scores (p=0.34). (The p value would need to be < 0.05 to reach the level of statical significance).
The Cochrane reviewers concluded that there is insufficient evidence to support the use of black cohosh for menopausal symptoms. So I think we all agree that this is essentially a ‘no’ vote for black cohosh.
But the story does not end there.
Fast-forward to 2013 when a group of German investigators re-crunched the data from the 2012 Leach paper and stated that ‘Our careful reconsideration of all appropriate placebo-controlled clinical studies reveals a standardised mean difference of 0.385 in favor of black cohosh (p < 0.0001)’.(9) That would be an overwhelming ‘yes’ vote using the same data.
But the story does not end there either.
A 2008 Italian meta-analysis of the literature relating to black cohosh for menopausal symptoms concluded ‘that while the evidence from these RCTs does not consistently demonstrate an effect of black cohosh on menopausal symptoms; a beneficial effect of black cohosh on peri-menopausal women cannot be excluded. The efficacy of black cohosh as a treatment for menopausal symptoms is uncertain and further rigorous trials seem warranted’. That sounds like a ‘maybe’ to me (10).
So we have a yes, no and maybe so.
Even the meta-analysis don't agree on the interpretation of the literature on black cohosh for menopause so we will have to say that there is no evidence that black cohosh helps menopausal symptoms.
Is It A Safe Alternative For Hormone Replacement Therapy?
The HALT study was designed to address this key question (11). Note the deliberate use of the word ‘designed’. Things did not exactly turn out as planned but this is still a useful study.
Researchers love acronyms and spend an unreasonable amount of time coming up with clever acronyms to describe their study. HALT stands for Herbal Alternatives for Menopause (though I have to say these researchers could have spent a little longer coming up with an acronym that included that letter M for menopause).
As the name (if not the acronym) suggests the aim of the study was to evaluate herbal alternative approaches to menopausal symptoms.
Women were randomly assigned to: (1) black cohosh 160 mg daily; (2) multibotanical (50 mg black cohosh, alfalfa, chaste tree, dong quai, false unicorn, licorice, oats, pomegranate, Siberian ginseng, boron) four capsules daily; (3) multibotanical plus telephone counseling to increase dietary soy; (4) conjugated equine estrogen 0.625 mg +/- 2.5 mg medroxyprogesterone acetate; or (5) placebo.
I studied under Dr Low Dog, one of the leading world experts on black cohosh in menopause who advises numerous committees and review bodies on the subject. She reviewed the details of the HALT study and I took out my lecture notes on the subject as she gives unique insights into the study
This was a 12 month federally funded study.
Dr Low Dog and her colleagues essentially discounted the data from the HRT arm due to the fact that the study stopped recruiting to this arm because of concerns regarding the safety of HRT in this population. They discounted the botanical arms as interim analyses showed that a number of the multi-botanical products used had no active ingredients.
The black cohosh arm of the study showed no benefit over placebo (another no vote).
There is no proof that black cohosh is a safe alternative to HRT.
Does It Treat Uterine Fibroids?
Two publications address the issue of black cohosh for fibroids.
I made an executive decision on behalf of #HBS to discount one of the studies as hopelessly inadequate (12).
The second study was a Chinese-German collaboration. A total of 244 Chinese women were randomized to either black cohosh 40 mg crude drug/day (N = 122) or tibolone 2.5 mg/day (N = 122) orally for 3 months (13). Tibolone is a selective oestrogen receptor modulator used in the medical management of fibroids.
There was a statistically significant decrease in the size of the uterine fibroids in the back cohosh group as compared to the tibolone group. A proprietary brand was used in the study but the investigators deny any financial conflict of interest.
A single study in Chinese woman with menopausal symptoms found that back cohosh was effective in reducing the size of fibroids. We cannot extrapolate that black cohosh would work for fibroids in women of all age-groups.
Is Black Cohosh (and or Supplementation) Safe?
There are some rare reports of liver toxicity. At least four of these cases of ‘black cohosh’ induced liver toxicity were actually due to mislabelling of the Asian species (Acta cumifuga) as black cohosh product.
Overall it is unclear as to how best to interpret the emerging ‘signal’ of black cohosh related liver toxicity.
The United States Pharmacopeia Dietary Supplements Expert Information Council has published a thorough review of adverse events related to black cohosh. Based on this safety review, the Dietary Supplement Information Expert Committee determined that black cohosh products should be labeled to include a cautionary statement (14).
Hence, it is recommend that women with liver disease discontinue the use of black cohosh, as should any woman who develops nausea, signs of symptoms suggestive of liver disease. Germany, Canda and Australia have similar instituted similar labelling requirements. Some countries like Ireland have taken it one step further and sale or importation of back cohosh related products are not permitted.
Adulteration of black cohosh with blue cohosh has been reported.
There are some theoretical concerns about black cohosh stimulating growth of breast tumors. This has not been borne out in clinical studies (15) However it is generally advised that people at risk of or with a history of breast cancer should avoid black cohosh.
A comprehensive review of black cohosh by Chinese researchers published last year in the Journal of Ethnopharmacology concluded that 'extensive study is required on Cimicifuga plant before it can be fully used in clinics as a potent drug candidate' (16).
Sounds like another way of saying 'yes, no, maybe so'.
The main indication for use of black cohosh today is for menopausal symptoms. As we have seen three independent reviewers analyzed the available data on black cohosh for menopause and concluded ‘yes, no and maybe so’.
What kind of research is this? Dr Low Dog describes this as a ‘mixed bag’ of results. (More like a lucky bag if you ask me).
Dr Low Dog gives her expert (and much more diplomatic) perspective on this and says that there are a number of reasons for these apparently inconsistent results:
Firstly, many of these studies included both menopausal and peri-menopausal women. Hormonally speaking, there is a very big difference between these two groups. In fact, there can be huge inter and intra-subject variation in hormones levels during the peri-menopause.
Secondly, there are differences between the formulations of black cohosh used. As an example, two of the leading proprietary brands have different extraction methods (ethanol and ispropanol) which can effect the results.
Dr Low Dog explains this may also explain why some women (in good faith and all sincerity) report positive benefits from black cohosh. That is wonderful. However, given the ‘mixed bag’ of results, we simply cannot in good conscience recommend black cohosh for everyone.
'Yes, no, maybe so' is no justification for harming the environment either.