Black Cohosh: Menopause ‘miracle’ or marauding danger?

If you’ve reached menopause you’ve faced the question of whether or not to try herbal remedies to relieve your nagging symptoms. And, if you’re like many women, you may have already found out that the answer is, unfortunately, anything but clear. In fact, you may have discovered that the available research on herbal approaches to menopause can be downright confusing, even conflicting at times, and that can leave you more confused than when you started. This is often the case with the popular menopause remedy black cohosh (Cimicifuga racemosa or Actea racemosa).

Black cohosh is dogged by safety concerns. One commonly mentioned issue is that the herb, like hormone replacement therapy (HRT), might have oestrogenic effects and as a result increase the risk of breast cancer in long-term users. Such fears have been fuelled by articles in the media and on the internet and a handful of scientific studies of, frankly, questionable relevance.

One such study was conducted in 2003 (although it wasn’t published until much later in 2008), researchers fed genetically-altered mature female mice a black cohosh extract at doses said to reflect the normal human dose for 12 months (which, actually, amounts to their whole adult life). While the incidence of mammary tumours was not increased by the herb, there was an increase in the number of tumours that spread to the lungs (27.1% of black cohosh-treated mice versus 10.9% of the control mice). According to the principal researcher Dr Davis: “Our findings suggest that women who may be at high risk of having an undetected breast tumour and certainly those who do have breast cancer should proceed with great caution – or simply avoid – taking black cohosh….”

Breast cancer benefits

At the time I suggested the logical thing to do for looking at any links between black cohosh and breast cancer would be to study the women actually already taking the herb. In fact, at that time there was one study already published showing that the breast cancer rate was in fact halved in black cohosh users. Now there are more studies, and they all show no link between black cohosh use and increased risk of breast cancer.

A German study involving 10,121 post-menopausal women found use of herbal products was inversely associated with invasive breast cancer (OR 0.74) in a dose-dependent manner. (An odds ratio (OR) of less than 1 indicates users are less likely to be at risk.) The two black cohosh product subgroups demonstrated moderate protection, but protection was most marked for chaste tree users (Vitex agnus-castus, OR 0.4). As part of the VITAL epidemiological study, 35,016 post-menopausal women were asked about their use of dietary supplements and followed for up to seven years. Black cohosh use was not found to be associated with an increased risk of invasive breast cancer, in contrast to that one widely publicised animal study.

Another study investigated breast cancer patients treated at German clinics. Of 18,861 patients, a total of 1,102 had received therapy with black cohosh. The average overall observation time was 3.6 years. Black cohosh was not linked with an increased risk of recurrence, but instead was associated with prolonged disease-free survival. This means, of course, that ALL of the studies looking at breast cancer risk or survival in human black cohosh users have found a possible benefit, not harm.

The liver damage link debunked

Another safety concern you’ll hear tied to black cohosh users from time to time is the sporadic reports linking it to liver damage. This doesn’t mean that black cohosh is toxic to the liver. Rather these are cases where black cohosh might have triggered an immune reaction in the liver leading indirectly to damage (most conventional drugs can do this to a greater or lesser extent in a small percentage of users).

In 2009, a German group headed by a medical specialist rigorously analysed all 69 reported cases of idiosyncratic liver toxicity attributed to black cohosh and found no likelihood of a causal link in 68. Most cases were marred by confounding variables, misreported data, and a lack of critical information. In particular, there was a lack of identification of the herb involved in the initial cases. Yes, that’s right, they couldn’t say for sure if black cohosh was even the herb being used by the women in some of the studies.

Of high relevance here are the findings of Health Canada. From January 2005 to March 2009, Health Canada received six domestic reports of liver damage suspected of being associated with black cohosh. But when the three products involved in these reports were analysed it was quickly revealed that they didn’t even contain any authentic black cohosh. In fact, their chemical profiles were consistent with the presence of other related herbal species. A follow-up review of the authenticity of all licensed products containing black cohosh resulted in the voluntary withdrawal of several products that did not in fact contain the herb, including those reported in four of the adverse reaction cases. Therefore any risk of liver damage from use of authentic black cohosh is likely to be quite rare.

To your better health,

Kerry Bone
Nutrition & Healing

Volume 7, Issue 2 – February 2013

Full references and citations for this article are available in the downloadable PDF version of the monthly Nutrition and Healing issue in which this article appears.

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