Menopause: Investigating the controversy surrounding black cohosh

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But despite the evidence, black cohosh has gotten a lot of bad press lately. Reports began to surface a few years ago indicating this popular herb could lead to liver damage.
If you've heard these stories, I'm sure you can't help but wonder whether you should pay any attention to them or simply dismiss them as just another example of mainstream medicines bashing of natural alternatives. I'd like to help you answer those questions by giving you the whole story.

Digging a little deeper

The European Medicines Agency Committee on Herbal Medicinal Products (HMPC) recently took a closer look at all the cases reporting an adverse reaction following use of the herb.

They evaluated 42 case reports of hepatotoxicity, collected from European National Competent Authorities (34 cases) as well as literature case reports (eight cases). Of these, only 16 cases were considered by the HMPC to be sufficiently documented to allow the committee to assess if use of black Cohosh could be linked to the liver injuries. As a result of the assessment, five cases were excluded and seven cases were considered unlikely to be related. In the remaining four cases there was a temporal association.

Of these four possible cases, only two were rated as probable by this expert committee, which evaluated the cases using a recognised procedure for rating cause and effect.

Case study #1: The first report describes the development of autoimmune hepatitis, which the authors claim was triggered by the use of black cohosh (Menopause 2004; 11(5): 575-577). A 57-year-old diabetic woman reported having experienced lethargy and fatigue for two weeks. Her medications for diabetes included labetalol, fosinopril, verapamil, metformin, aspirin, and insulin. Three weeks before she experienced these symptoms, she began taking black cohosh tablets for hot flushes. The doctors diagnosed her with drug-induced autoimmune hepatitis and attributed it to the black cohosh.

She stopped using the herb and began taking a tapering steroid course. Within two weeks, her symptoms went away and follow up tests revealed that her liver function tests (LFTs) were normal again. However, at four months the woman returned with a complaint of jaundice and fatigue, and further tests revealed that her LFTs were abnormal again. Once again, the doctors put her on a course of steroids. Again, the patient rapidly improved.

Case study #2: The next case report was that of a 50-year-old woman suffering from acute onset jaundice (Dig Dis Sci, 2005; 50(3): 538-539). The provisional diagnosis was autoimmune hepatitis, since tests for hepatitis A, B, and C, cytomegalovirus, and Epstein-Barr virus were all negative. In the five months prior to the onset of jaundice, the patient had been taking 500mg of black cohosh daily for menopausal symptoms and was not on any other medications. Because the patient failed to respond to initial treatment, she had a liver transplant. When her liver was removed, it showed features of acute hepatitis.

Decoding the details of the evidence against black cohosh

As you can probably see, these two published case histories are full of flaws. For the first case, the woman was not even using black cohosh the second time she began to have liver problems, yet the doctors still placed the blame on the herb. In addition, they claimed that none of the patients other medications had been linked to autoimmune hepatitis. Yet a simple search on PubMed revealed several cases in which labetalol may have caused idiosyncratic autoimmune hepatitis, including one overview report of 11 cases from the US Food and Drug Administration (J Clin Hypertens 2002; 4(2): 120-121; Neth J Med 1992; 40(3-4): 200-202; Ann Intern Med 1990; 113(3): 210-213).

In the second case, the authors attribute the presence of hepatotoxic alkaloids and salicylates to black cohosh. Such attributions are nonsensical, are unsupported by the literature (and were deemed unlikely by the expert committee), and above all cast doubt on the credibility and diligence of their overall analysis of the case.

In fact, Case 2 was the subject of a lawsuit that was thrown out of court. The main reason for this was that under cross-examination it was revealed that the patient had been taking three other medical drugs that were known to cause the type of liver damage she experienced. None of these drugs were mentioned in the original article. In fact, the original article specifically stated that the patient was NOT taking any other drugs or herbs.

So when it comes right down to it, even the probable cases as rated by the expert HMPC committee are, in fact, highly improbable.

Anti-herbal conspiracy or unfortunate coincidence?

I think the sad reality is that black cohosh has been found guilty by association.
Research in several countries has determined that one of the most serious causes of liver damage is still unknown. They call this idiopathic hepatitis (J Gastroenterol Hepatol 2004; 19(2): 154-159; Hepatology 1995; 21: 240-252). Demographics for idiopathic hepatitis and black cohosh use strongly overlap females between their late 30s and early 50s. Hence, there is a distinct possibility that some patients who develop idiopathic hepatitis might also be coincidentally taking black cohosh. In those cases, the herb could be mistakenly attributed as the cause when it really has nothing to do with it.

Another issue is the quality of the black cohosh products. Neither of the two US case studies reported the make of black cohosh that each woman used. And lately, the botanical authenticity of black cohosh products has become a serious issue in the US (J Agric Food Chem 2006; 54: 3242-3253).

The bottom line is that the association of authentic black cohosh and liver damage remains unproven on the basis of any current evidence. You should take about 100 to 500mg of root per day. Authentic products include those made in Western Europe and Australia, where a strict code of pharmaceutical good manufacturing practices is applied by law to herbal products.