Does Black Cohosh Cause Breast Cancer?

Hi, everybody.  I’m posting about black cohosh because a patient was upset that I recommended she try that supplement for her menopausal hot flashes.  She was reluctant to try traditional hormone replacement (which I understand, since PRESCRIBING it makes me nervous because of the risks) so I figured a nonhormonal supplement would be a great place to start.  She was very upset because she was under the impression it increased the risk of breast cancer.

Off I went to the National Institutes of Health’s PubMed database, which is where I go for research data.  Here’s what I found:

1.  A German study published in 2009 followed over 10,000 women and looked at their use of herbal products containing black cohosh and phytoestrogens (red clover and soy isoflavones) among other products.  They found that use of these herbal products was associated with a modest reduction in the risk of breast cancer and that the longer these products were used the larger the reduction in risk.  Note:  this was not a study designed to determine a CAUSAL relationship.

2. A really big study (more than 35,000 women) from Washington State  published in Cancer found no increased risk of breast cancer in women taking a variety of supplements including black cohosh, dong quai, soy, and St. John’s wort.  Interestingly, breast cancer was lower in women taking fish oil supplements.

3. Here’s my nod to basic science.  A group at Columbia University found that an extract of black cohosh applied to human breast cancer cells was able to induce cell death in those cancer cells.  They theorize that black cohosh may actually have a role in the prevention and treatment of breast cancer.

There is a lot of confusing information out there about supplements and cancer risk.  My (not exhaustive by any means) search of the database didn’t turn up any evidence that black cohosh causes breast cancer, but new studies are being published every day and everyone should choose the medications and supplements they take with advice from their doctor.  As always, interactions and risks are present no matter what you do.

I included the links above to the studies I mentioned so that anyone who wants more information can follow up.  I picked studies that have full-text articles available for free, just follow the links.

Be careful out there!


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