The study, published in the International Journal of Cancer , needs significant support from future studies before it can be recommended as a breast cancer preventative, but the research could offer a new avenue of research for the herb most commonly used by women to reduce menopausal symptoms such as hot flushes.
Black cohosh (referred to by the European Medicines Agency, or EMEA, as Cimicifugae racemosae rhizome ) is a member of the buttercup family, and is a perennial plant native to North America.
Historically it has been a popular alternative to hormone replacement therapy (HRT) in many countries including the UK, where it is estimated that 9 million days worth of black cohosh supplements were purchased in 2004.
"Hormone-related supplements (HRS), many of which contain phytoestrogens, are widely used to manage menopausal symptoms, yet their relationship with breast cancer risk has generally not been evaluated," explained lead author Timothy Rebbeck from University of Pennsylvania School of Medicine.
The researchers 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.
Rebbeck and co-workers report that herbal use was more prevalent among African American women than European American women (19.2 versus 14.7, respectively), as well as specific preparations including red clover (4.7 versus 0.6 per cent), black cohosh (5.4 versus 2.0 per cent), and ginseng (12.5 versus 7.9per cent, respectively).
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, said the researchers.
This risk reduction was also observed for Remifemin, a herbal preparation derived from black cohosh, which was calculated to reduce the risk of breast cancer by 53 per cent.
"Substantial additional research must be undertaken before it can be established that black cohosh, or some compound found in black cohosh, is a breast cancer chemopreventive agent," wrote the researchers.
"Furthermore, women may wish to seek guidance from their physician before using these compounds," they concluded.
Previously, concerns have been raised about breast cancer patients taking black cohosh supplements in order to alleviate the menopause-like side effects.
Researchers from Yale School of Medicine reported that black cohosh might interact detrimentally with chemotherapy by increasing cytotoxicity (cell killing) by two of the drugs, doxorubicin and docetaxel.
It decreased the cytotoxicity of cisplatin.
Over one million women worldwide are diagnosed with breast cancer every year, with the highest incidences in the US and the Netherlands.
China has the lowest incidence and mortality rate of the disease.
Source: International Journal of Cancer 1 April 2007, Volume 120, Issue 7, Pages 1523-1528, doi: 10.1002/ijc.22485 "A retrospective case-control study of the use of hormone-related supplements and association with breast cancer"
Authors: T.R. Rebbeck, A.B. Troxel, S. Norman, G.R. Bunin, A. DeMichele, M. Baumgarten, M. Berlin, R. Schinnar, B.L. Strom