Black cohosh contains several ingredients, including triterpene glycosides (for example, acetin and 27-deoxyactein) and isoflavones (for example, formononetin). Other constituents include aromatic acids, tannins, resins, fatty acids, starches, and sugars. As a woman approaches menopause, the signals between the ovaries and pituitary gland diminish, slowing down estrogen production and increasing luteinizing hormone (LH) secretions. Hot flashes can result from these hormonal changes. Earlier animal studies15, 16 and a human clinical trial17 suggested that black cohosh had some estrogen activity in the body and also decreased LH secretions. However, more recent animal studies18 and a clinical trial19 have found no estrogen activity for black cohosh extracts. Further clinical trials are needed to determine whether black cohosh has significant estrogenic actions in the body.
Small German clinical trials support the usefulness of black cohosh for women with hot flashes associated with menopause.20, 21 A review of eight clinical trials found black cohosh to be both safe and effective for symptomatic relief of menopausal hot flashes.22 Other symptoms which improved included night sweats, insomnia, nervousness, and irritability. A clinical trial compared the effects of 40 mg versus 130 mg of black cohosh in menopausal women with complaints of hot flashes.23 While hot flashes were reduced equally at both amounts, there was no evidence of any estrogenic effect in any of the women. Although further trials are needed, this trial suggests that black cohosh is best reserved only for the symptomatic treatment of hot flashes associated with menopause and is not thought to be a substitute for hormone replacement therapy in menopausal and postmenopausal women.
A recent study suggests black cohosh may protect animals from osteoporosis.24 Human studies have not confirmed this action.