A member of the buttercup family, black cohosh, or Actaea racemosa (formerly named Cimicifuga racemosa), is primarily recognized as a phytoestrogenic compound for menopausal symptoms, specifically hot flushes, sleep and mood disturbances, and vaginal dryness. Growing as high as eight feet and producing long clusters of white blossoms, the plant is native to eastern North American forests, from Ontario to Georgia. Its thick, knobby, resin-scented root contains its medicinal properties.1


Used by the Cherokee to treat rheumatism and various gynecologic conditions, black cohosh was one of the mainstays of Native-American folk medicine. This herb was rapidly adopted by our country’s early settlers and eventually found its way to continental Europe, where it became equally popular.2 In Germany, it is used not only for hot flushes but also depression and sleep disturbances. The root was an official drug of the United States Pharmacopoeia from 1820 to 1926; early editions gave its official name as “black snakeroot,” a moniker that persisted in medical texts until the 1890s. If John King, MD, a professor of obstetrics at the now-closed Eclectic Medical College in Cincinnati, had not been such an enthusiastic proponent, the herb might have faded into obscurity. He used the root for inflammatory conditions but recognized it as his primary therapy “in abnormal conditions of the principal organs of reproduction in the female.”3

The herb’s roots and rhizomes, or underground stem structures, are pulverized and the active ingredient extracted. The identity of that ingredient remains uncertain; commercial products contain an extract of standardized 26-deoxyactein, a chemical from the group known as “saponins.” Most formulations are in 20-mg capsules and contain 1 mg of triterpene saponins.4


There have been several studies of black cohosh, but most have been weakly designed, lacking placebo controls. The trials usually measure menopausal symptoms subjectively. Several noncontrolled trials have shown mild improvement in hot flushes and other symptoms, but other studies have not.1 Only one trial revealed any impact on actual hormone levels, but it was noncontrolled, with no record of participants’ pretrial hormones.1 Nevertheless, in 2001, the American College of Obstetricians and Gynecologists issued a statement in support of short-term use (six months or less) of black cohosh for vasomotor symptoms.5

NIH’s National Center for Complementary and Alternative Medicine is funding clinical trials to determine the safety and efficacy of the herb. One major trial ended in July 2005, and the summation report is due soon. Several other NIH-sponsored trials are in progress.2

Mechanism of action

Researchers have used the definition of phytoestrogen as meaning a substance that promotes actions commonly defined as estrogenic. Many plants contain phenolic phytoestrogens. The three main groups of these are isoflavones, lignans, and coumestans. It is believed that black cohosh contains isoflavones that enhance estrogenic activity. Since estrogen levels during menopause are not absent, but merely decreased, any mechanism that enhances the remaining estrogenic function would serve to alleviate the deficit. This function is felt to explain black cohosh’s effect on hot flushes, heart palpitations, night sweats, and sleep disturbances associated with menopause.6

Some researchers believe that the plant is not estrogenic at all but might enhance serotonin.6 Selective serotonin reuptake inhibitors as a drug class have long been recognized as useful in controlling menopausal vasomotor symptoms.


Because of its possible weak estrogenic effects, black cohosh is not recommended for anyone who has breast cancer or is pregnant. Women with other estrogen contraindications — such as the presence or risk of thromboembolism, stroke, or migraine with aura — also should be considered at risk for estrogenic complications, so their use of this product is not advised. There have been very few studies of sufficient power and design to adequately establish safety in breast cancer patients and pregnant women.7


The recommended dose is 20 mg of whole plant extract taken morning and evening in pill or capsule form.1 Maximum effects usually occur in four to eight weeks.

Side effects

Botanical allergies are always a possibility when using plant products, so women with significant atopic histories should proceed cautiously. Occasional GI upset and headaches have been reported. Large doses of the herb have also been known to cause dizziness, nausea, and vomiting. In trials comparing the effects of black cohosh with those of estrogen, heaviness in the legs and weight problems were also reported.5

There are no known drug interactions.5 Black cohosh should not be confused with blue cohosh, a different plant used by midwives to induce labor. The two herbs have sometimes been used together during delivery, but there are documented cases of neonatal damage with this practice.5 Current studies have only examined short-term use of black cohosh (six months or less), so its long-term safety is unknown.


A month’s supply of the herb will cost from $8 to $15, depending on where it is purchased.

Bottom line

Black cohosh is a relatively safe and mildly effective herbal therapy for managing menopause symptoms. There are no data to support its use for preventing osteoporosis.


1. Questions and Answers About Black Cohosh and the Symptoms of Menopause. Available at ods.od.nih.gov/factsheets/BlackCohosh.asp. Accessed May 8, 2006.

2. Wade C, Kronenberg F, Kelly A, Murphy PA. Hormone-modulating herbs: implications for women’s health. J Am Med Womens Assoc. 1999;54:181-183.

3. Foster S. Black Cohosh. Available at www.stevenfoster.com/education/monograph/bkcohosh.html. Accessed May 8, 2006.

4. Chen SN, Li W, Fabricant DS, et al. Isolation, structure elucidation, and absolute configuration of 26-deoxyactein from Cimicifuga racemosa and clarification of nomenclature associated with 27-deoxyactein. J Nat Prod. 2001;65:601-605.

5. Herbs at a Glance: Black Cohosh. Available at nccam.nih.gov /health/blackcohosh. Accessed May 8, 2006.

6. Fitzpatrick LA. Menopause and hot flashes: no easy answers to a complex problem. Mayo Clin Proc. 2004;79:735-737.

7. Black Cohosh (Cimicifuga racemosa [L.] Nutt). Available at www.mayoclinic.com/health/black-cohosh/NS_patient- blackcohosh. Accessed May 8, 2006.