Black Cohosh, Cysteine Studied in Breast Cancer

WASHINGTON, D.C.--Two studies presented at the 94th Annual Meeting of the American Association for Cancer Research (www.aacr.org), held July 11 to 14, shed light on herbs, antioxidants and breast health. In one study, conducted by researchers from Duquesne University, Pittsburgh, it was found black cohosh might not be safe for women who have undetected breast tumors. In research led by Vicki Davis, Ph.D., black cohosh was given to mice at a level of 40 mg/d (the amount normally recommended for menopausal symptoms) for 12 months; at the same time, researchers triggered breast tumor growth in the animals. Although the incidence of new tumors did not increase in black cohosh-treated female mice, mice taking the herb that did develop mammary tumors had an increased risk of tumors spreading to the lung (27.1 percent of treated mice compared to 10.9 percent on the control diet).

"Our findings suggest that women who may be at high risk of having an undetected breast tumor and those who do have breast cancer should proceed with great caution, or simply avoid, taking black cohosh until we learn if there are ways to circumvent these adverse effects," Davis reported.

In another study presented at the meeting by researchers from Harvard University, Boston, indicated high cysteine levels may be associated with a lower risk of breast cancer. The case-controlled study was conducted among 33,000 women participating in the Nurses' Health Study. Of this number, 712 incidents of breast cancer were matched to 712 controls by birth year; scientists then used conditional logistic regression with adjustment for other breast cancer risk factors to estimate the relative risks for breast cancer by levels of plasma total cysteine. "The findings suggest that higher levels of total cysteine may predict a reduced risk for breast cancer," said Shumin Zhang, M.D., Sc.D., lead investigator. "Based on these results, we are hopeful that cysteine or its precursors [such as N-acetylcysteine] may have potential chemopreventive benefits against breast cancer."