Black Cohosh: doesn't work for hot flashes but cuts cancer risk by half

Jacob Schor, ND

May 10, 2007



Root extracts of black cohosh, have taken a roller coaster ride in the scientific literature over the last few months. Apparently, women who took black cohosh to reduce hot flashes wasted their time but unknowingly cur their breast cancer risk in half.


T he herb black cohosh, or Actaea racemosa (formerly named Cimicifuga racemosa), is native to North America. The roots and rhizomes are widely used in the treatment of menopausal symptoms and menstrual dysfunction. Black cohosh was originally used by Native American peoples in the treatment of many conditions, especially gynecologic disorders. The most widely used and best studied commercial formulation available in the United States is Remifemin, an extract of the rhizome that is produced by a German company. Numerous other brands of black cohosh are available, but not all are standardized extracts. [i]


At least we thought these extracts were useful for treating menopausal symptoms and numerous studies supported this contention until early this year when the HALT study was published.


“The Herbal Alternatives for Menopause (HALT) trial randomly assigned 351 peri- or postmenopausal women, ages 45 to 55, to one of five groups: 160 milligrams of black cohosh daily; 200 milligrams of black cohosh daily in a multibotanical supplement; multibotanical supplement plus diet counseling to boost soy consumption; menopause hormone therapy; or placebo.

The women were evaluated for severity of hot flashes (vasomotor symptoms) at three, six and 12 months. The researchers found no significant difference between the placebo and any of the herbal treatments, except that the supplement-plus-soy group actually experienced significantly worse symptoms at 12 months. Women on hormone therapy, which has been linked to increased risk of heart attack and breast cancer, had 4.06 fewer symptoms per day on average. [ii]

“ Black cohosh used in isolation, or as part of a multibotanical regimen, shows little potential as an important therapy for relief of vasomotor symptoms," concluded lead author Katherine M. Newton, PhD, of Group Health system in Seattle .

But an accompanying editorial by Carol M. Mangione, MD, added a hopeful note: "Women in the placebo group experienced an approximately 30% reduction in the severity and frequency of vasomotor symptoms during the 12-month follow-up period," she noted.' " [iii]


Before you throw away your bottle of Black Cohosh, there is more to this story. In the April issue of the International Journal of Cancer, researchers reported that women who had taken black cohosh cut their risk of developing breast cancer in half.

Timothy Rebbeck from University of Pennsylvania School of Medicine and his colleagues used a population-based case-control study consisting of 949 breast cancer cases and 1,524 controls. Demographic information and the use of hormone-related supplements were identified using questionnaires.

After adjusting for potential confounding factors the use of black cohosh was associated with a 61 per cent reduction in the risk of breast cancer. This risk reduction was also observed for Remifemin, the herbal preparation derived from black cohosh, which was calculated to reduce the risk of breast cancer by 53 per cent. [iv]

This shouldn't be that surprising. A 2002 study told us that cohosh extracts significantly inhibited the growth of breast cancer cells with or without the presence of estrogen and if given at the same time, enhanced the effect of tamoxifen at inhibiting cancer cell growth. [v]

Black cohosh has often been suggested to breast cancer patients to help control their hot flashes as it has been generally assumed safe and without a cancer stimulating effect. A study published in March 2007 looked at this practice. The researchers analyzed 18,861 breast cancer patients, of whom 1,102 had taken black cohosh. Their results showed that taking black cohosh was associated with prolonged disease-free survival. After 2 years following initial diagnosis, 14% of the control group had developed a cancer recurrence. It took 6.5 years for cohosh takers to reach this same proportion of recurrences. Comparing the two groups, the cohosh users had a rate of recurrence that was 83% of the nonusers. [vi]

Cohosh may not work any better than a placebo at reducing hot flashes, but then again the placebo reduced hot flashes by 30%. If cohosh does reduce risk of breast cancer by 53 to 61%, or if it reduces rate of recurrence by 17%, do we really care what it does for hot flashes? If these benefits prove to be true in larger studies, cohosh is well worth the expense both for preventing breast cancer and as an adjunctive treatment for those with a history of breast cancer. So far, we haven't found a placebo that cuts the risk of cancer by half.




[i] American Family Physician July 1, 2003

[ii] Newton KM, et al. Treatment of vasomotor symptoms of menopause with black cohosh, multibotanicals, soy, hormone therapy, or placebo: a randomized trial. Ann Intern Med. 2006 Dec 19;145(12):869-79.

[iii] Black Cohosh Fails to Relieve Menopause Symptoms.   Tufts University Health & Nutrition Letter, 15260143, Mar2007, Vol. 25, Issue 1

[iv] Rebbeck TR, et al. A retrospective case-control study of the use of hormone-related supplements and association with breast cancer. Int J Cancer. 2007 Apr 1;120(7):1523-8.

[v] Bodinet C, Freudenstein J. Influence of Cimicifuga racemosa on the proliferation of estrogen receptor-positive human breast cancer cells Breast Cancer Res Treat. 2002 Nov;76(1):1-10.

[vi] Zepelin HH, ete al. Isopropanolic black cohosh extract and recurrence-free survival after breast cancer.

Int J Clin Pharmacol Ther. 2007 Mar;45(3):143-54