Black cohosh, a member of the buttercup family, is native to North America. The roots and rhizomes are used to alleviate hot flashes and other symptoms of menopause. Aside from its use in women's health, it has historically been used to treat kidney and lung disorders, neurological conditions, rheumatism, constipation and hives.There is some controversy over certain potential harmful effects of black cohosh.
There has been concern about black cohosh having potential toxic effects on the liver resulting in a form of autoimmune hepatitis. A review of 69 reported cases of black-cohosh–induced hepatitis was published in the March 2010 journal "Menopause." The study reported that the data did not support the association between hepatitis and black cohosh as the causative factor in these cases, citing such problems as poor case data quality, undisclosed indication, lack of temporal association, missing or inadequate evaluation of alcohol use, comedication--administration of other medications which may interfere with results, comorbidity--presence of concurrent disease, and alternative diagnoses. Another study of the same 69 cases, published in the October 20, 2009, "Maturitas," came to a similar conclusion of little to no supportive evidence of hepatotoxicity from black cohosh use.
A study on the effects of black cohosh on breast cancer development and progression in mice concluded that black cohosh did not contribute to the formation of cancer in cancer-free test animals. The study, published in the October 2008 journal "Cancer Research," also reported, however, that black cohosh significantly increased the incidence of lung metastases in animals with preexisting breast cancer. The researchers caution that more research needs to be done on the effects of black cohosh at specific times during breast cancer development and that extended use of this herb is unwarranted. Another study, published in the 2007 "Nutrition and Cancer" looked at the oestrogenic effect of black cohosh and found that the herb relieved menopause symptoms without exerting a cancer-promoting oestrogenic effect on cells in the breast or throughout the body.
Minor side effects and considerations
Toxicity of black cohosh is low, and the herb is generally well tolerated, with few side effects, if any, according to the website HerbalSupplementsGuide.com. When side effects do occur, they are minor and reversible. Headaches, dizziness and nausea are some of the commonly encountered side effects of black cohosh and are similar to the types of minor adverse effects seen with many other herbs and drugs. Like all supplements, black cohosh is not standardised or regulated to the same extent as conventional medicines, so the amounts of active ingredient stated on the bottle may not be accurate. Contaminants can sometimes be present in nutritional supplements as well, and it is important to be familiar with the source in order to be assured of reliability.