With the constant stream of conflicting information regarding what substances cause cancer, it is normal for people to worry about the cancer risks of using medications and herbal supplements such as black cohosh. While MedlinePlus explains that black cohosh is likely safe for healthy adults, there are some concerns regarding its use and links with cancer. Always consult your physician before using black cohosh or any other herbal supplement.
Exacerbation of Existing Cancers
Black cohosh contains plant-based substances that mimic the hormone estrogen. Estrogen comprises a group of compounds -- including estradiol, estrone and estriol -- that share similar characteristics. Estrogen occurs in both men and women and is important for developing secondary sexual characteristics. In women, estrogens circulate and bind to receptors, affecting the breasts, uterus, brain, bones, heart and liver. Estrogen plays an important role in reproduction and, during menopause, estrogen levels decrease. In men, estrogen helps maintain bone density and plays a role in sex drive.
Many cancers are hormone-based, including ovarian, breast and uterine cancers in women as well as prostate cancer in men. The University of Maryland Medical Center states that black cohosh may exacerbate these conditions because of its estrogen-like properties. However, there is insufficient evidence to draw any definitive conclusions.
Interference With Cancer Medications
Black cohosh can interact with a number of medications, including the drug tamoxifen, which is commonly prescribed to help treat breast cancer. Tamoxifen belongs to a class of drugs known as anti-estrogens and blocks the activity of estrogen in the breast and helps inhibit the growth of tumors that need estrogen to grow. The estrogen in black cohosh may interfere with tamoxifen's ability to inhibit tumor growth, according to MayoClinic.com. It is unclear whether black cohosh does interfere with tamoxifen due to a lack of human clinical trials and an unclear picture of the true mechanism of action of the herbal supplement. However, avoid the use of black cohosh if you have breast cancer and speak to your oncologist before using this herbal supplement.
Breast Cancer Risks
There seems to be a great deal of conflicting information regarding whether black cohosh stimulates the growth of breast cancer cells. The University of Maryland Medical Center explains that human clinical trials have produced mixed results with some studies showing that black cohosh causes breast cancer cells to grow and other studies showing that black cohosh inhibits the growth of breast cancer cells. Though the results are mixed, researchers recommend avoiding the use of black cohosh if you have a history of breast cancer or there is a history of breast cancer in your family. If you choose to use black cohosh with a breast cancer history, you should do so under the supervision of a physician.
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