Menopause and Black Cohosh

Black cohosh’s main use today is for the treatment of menopausal symptoms. Some evidence indicates that black cohosh extract might reduce hot flashes as well as other symptoms of menopause.

In the past, black cohosh was believed to be a phytoestrogen, a plant-based substance that behaves in a similar way to estrogen. However, growing evidence indicates that black cohosh does not have general estrogen-like actions. Rather, it may act like estrogen only in certain places:

• the brain (reducing hot flashes)
• the bones (potentially fighting osteoporosis)
• the vagina (reducing vaginal dryness)

It does not appear to act like estrogen in the breast or the uterus. If these findings about black cohosh's effects are reliable, then black cohosh is a selective-estrogen receptor modifier (SERM) somewhat like the drug raloxifen (Evista).

Read more details about Black Cohosh.

A 12-week, double-blind, placebo-controlled trial of 304 women with menopausal symptoms found that black cohosh was more effective than placebo in reducing number of hot flashes.

Promising results were also seen in a 3-month, double-blind study of 120 menopausal women. Participants were given either black cohosh or fluoxetine (Prozac). Over the course of the trial, black cohosh proved more effective than fluoxetine for hot flashes, but fluoxetine was more effective than black cohosh for menopause-related mood changes.

Previous smaller studies have found improvements not only in hot flashes but also in other symptoms of menopause. For example, in a double-blind, placebo-controlled study, 97 menopausal women received black cohosh, estrogen, or placebo for 3 months. The results indicated that the herb reduced overall menopausal symptoms (such as hot flashes) to the same extent as the drug. In addition, microscopic analysis showed that black cohosh had an estrogen-like effect on the cells of the vagina. This is a positive result because it suggests that black cohosh might reduce vaginal thinning. However, black cohosh did not affect the cells of the uterus in an estrogen-like manner; this too is a positive result, as estrogen’s effects on the uterus are potentially harmful. Finally, the study found hints that black cohosh might help protect bone.

A study reported in 2006 found that black cohosh has weak estrogen-like effects on vaginal cells and possible positive effects on bone. Specifically, the herb stimulated new bone formation, preventing or even possibly reversing osteoporosis.

One interesting double-blind study evaluated a combination therapy containing black cohosh and St. John's wort in 301 women with general menopausal symptoms as well as depression. The results showed that use of the combination treatment was significantly more effective than placebo for both problems.

A smaller study using a combination of the same two herbs found improvements in overall menopausal symptoms as well as cholesterol profile.

The bottom line: Black cohosh may be modestly effective for reducing hot flashes and other symptoms of menopause.

Safety Issues

Black cohosh seldom produces any side effects other than occasional mild gastrointestinal distress. One rigorous study looked for possible deleterious effects on cholesterol levels, blood sugar, and blood coagulability, and did not find any.

Studies in rats have found no significant toxicity when black cohosh was given at 90 times the therapeutic dosage for a period of 6 months. Since 6 months in a rat corresponds to decades in a human, this study appears to make a strong statement about the long-term safety of black cohosh.

Unlike estrogen, black cohosh does not stimulate breast cancer cells growing in a test tube. However, black cohosh has not yet been subjected to large-scale studies similar to those conducted for estrogen. For this reason, safety for those with previous breast cancer is not known. Also, because of potential hormonal activity, black cohosh is not recommended for adolescents or pregnant or nursing women.

There are a growing number of case reports in which it appeared that use of a black cohosh led to severe liver injury. However, it is not clear whether the cause was black cohosh itself, or a contaminant present in the product.

One highly preliminary study found that black cohosh might reduce the effectiveness of the chemotherapy drug cisplatin.

Safety in young children or those with severe liver or kidney disease is not known.

Black cohosh should not be confused with blue cohosh (Caulophyllum thalictroides), which has different properties, treatment uses, and side effects. Black cohosh is sometimes used with blue cohosh to stimulate labor, but this therapy has caused adverse effects in newborns, which appear to be due to blue cohosh.

Interactions You Should Know About

Black cohosh might reduce the effectiveness of cisplatin.

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