Despite the widespread perception that herbal products are safe because they are “natural,” few products have been subjected to rigorous research. The potential risks of taking many herbal dietary supplements are not known. A perennial herb native to eastern North America, black cohosh was developed originally by Native Americans as a remedy for menstrual and menopausal conditions. The liquid extract prepared from its roots and rhizomes is used today as a dietary supplement for the relief of menopausal symptoms and other gynecologic disorders. It is also available in tea, capsule, and tablet forms from health food stores, drug stores, and online. Although black cohosh appears to alleviate menopausal symptoms, there is insufficient evidence that it is safe for breast cancer. Studies suggest that, unlike many herbs used as substitutes for hormone replacement therapy, black cohosh does not possess estrogenic activity. Instead, its effects may occur via an estrogen-independent pathway, possibly through HER2 signaling.
Whether black cohosh has no estrogenic activity requires more definitive research. Until then, patients with estrogen receptor–positive cancers are best advised not to use it.
—Barrie Cassileth, PhD
SUPPLEMENT: Black cohosh (Cimicifuga racemosa)
ALSO KNOWN AS: Black snakeroot, rattlesnake root, squawroot
USES: To treat psoriasis, scleroderma, seasonal affective disorder, and to prevent osteoporosis and cancer
RESEARCH: Many randomized controlled trials demonstrate that black cohosh effectively treats menopausal symptoms. In vitro studies show that black cohosh has proapoptotic and antiproliferative effects.[1,2] But it increased metastatic mammary cancer in mice, which may be due to its actions as a partial agonist of serotonin, dopamine(Drug information on dopamine), and mu-opioid receptors. Whether it has similar effects in breast cancer patients is not well studied, although a retrospective observational study of breast cancer patients found that black cohosh increased disease-free survival.
Clinical trial data show that black cohosh is effective alone or in combination with other herbs for the treatment of menopausal symptoms. Trials evaluating black cohosh for hot flashes due to breast cancer treatment yielded mixed results.[7,8] Further research is needed.
ADVERSE REACTIONS: Gastrointestinal upset and rashes are most common; dizziness, headaches, nausea, and vomiting may occur when higher than recommended doses are consumed. Hepatotoxicity has been reported following use of black cohosh.[10,11]
HERB-DRUG INTERACTIONS: Tamoxifen(Drug information on tamoxifen): Black cohosh may have an additive antiproliferative effect.
Cytochrome P450 3A4: Black cohosh may interact with drugs that are metabolized by CYP3A4 enzyme.