How It Works
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.
How to Use It
Black cohosh can be taken in several forms, including crude, dried root or rhizome (300–2,000 mg per day), or as a solid, dry powdered extract (250 mg three times per day). Standardized extracts of the herb are available. The recommended amount is 20–40 mg twice per day.25 The best researched extract provides 1 mg of deoxyactein per 20 mg of extract. Tinctures can be taken at 2–4 ml three times per day.26 According to the German Commission E Monographs, black cohosh can be taken for up to six months, and then it should be discontinued.27
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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2015.