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Black Cohosh

Other common name(s): black snakeroot, bugbane, bugwort, Remifemin®

Scientific/medical name(s): Cimicifuga racemosa or Actaea racemosa


Black cohosh is a perennial woodland plant that is a member of the buttercup family. It grows in the eastern United States and Canada. Black cohosh grows from 4 to 8 feet tall and has feathery white flowers. The root is used in herbal remedies.


Available scientific evidence does not support claims that black cohosh is effective in treating cancer. Some studies suggest it might interfere with some drugs used in chemotherapy. The safety of long-term use is not known. Serious side effects are rare but have been reported.

There is inconsistent evidence regarding whether black cohosh is effective in relieving menopausal symptoms for women in general. Its safety and effectiveness for women with menopausal symptoms caused by treatment of breast cancer is also not clear.

Doctors are not sure how black cohosh might work. It contains several chemicals that may have effects in the body.

How is it promoted for use?

Black cohosh is often referred to as a "woman's remedy" because it is used mainly to relieve premenstrual problems, menstrual cramps, and symptoms of menopause such as hot flashes. Commission E (Germany's regulatory agency for herbs) has approved black cohosh for these symptoms. Black cohosh is also a source of vitamin A and pantothenic acid.

In the past, the helpful effects of black cohosh were thought to be due to chemicals in the plant that resemble and mimic the effects of the female hormone called estrogen. However, the strength of the plant's estrogen-like effects has been disputed, and the exact way black cohosh works in the body is not well understood.

Because some types of cancer, such as breast, uterine, ovarian, and endometrial cancer, may be stimulated by estrogen, some herbalists state that black cohosh may be dangerous for people who have cancer. But another view holds that since the herb does not actually contain estrogen, it is safe for cancer patients. Some promoters of black cohosh state that the herb reduces the risk of breast and prostate cancer.

Black cohosh has also been used to treat pain before, during, and after childbirth; breast pain; ovarian pain; and uterine pain. Other reported uses of black cohosh include arthritis pain relief, lowering blood pressure, sedation, treatment of bronchial infections, treatment for spasms associated with whooping cough, and treatment of diarrhea.

What does it involve?

Black cohosh is the main ingredient in an over-the-counter German menopausal remedy called Remifemin. In addition, black cohosh can be found in several different forms including capsules, solutions, tablets, tinctures, and powders.

There is no standardized treatment plan for the use of the herb. The typical dose suggested is 20 to 200 milligrams daily, 1 to 2 grams of dried root powder, or 10-60 drops of tincture a day. It can also be made into a tea.

What is the history behind it?

Cohosh is a Native American word that means "knobby rough roots," which describes the appearance of the plant's roots. Native Americans used black cohosh to treat uterine disorders such as menstrual and menopausal symptoms, as well as other ailments, such as diarrhea, sore throat, arthritis, and general weakness. The herb has been approved in Germany for the same purposes for more than 50 years and is commonly prescribed in other European countries.

What is the evidence?

There is inconsistent evidence of effectiveness from clinical trials. Some studies report that black cohosh relieves menopausal symptoms while others do not. Some of the disagreement may be due to differences in the herbal products tested, as well as how the studies are done.

A 2005 study of 304 women found that, compared to a placebo (inactive or sham pill), black cohosh helped symptoms of menopause. It seemed more effective for women whose symptoms had begun recently than for those who had been post-menopausal for a longer time.

On the other hand, a 2006 study of 351 women found that menopausal symptoms were helped by hormone therapy but not by black cohosh (either alone or with other herbs). Clinical trial results published in 2008 reported no difference between black cohosh and placebo regarding vaginal dryness, menstrual irregularity, female hormones, or the structure of vaginal cells in Pap test samples.

Another study done in 2009 compared black cohosh to placebo, conventional hormone therapy (estrogen and progesterone), and red clover (another popular herb for the relief of menopausal symptoms). The study looked at 89 healthy women who were randomly assigned to one of the 4 groups and did not know which treatment they were getting. The study found that black cohosh was actually significantly less effective than placebo in reducing symptoms. But the standardized extracts used in the study seemed to be safe for the participants during the 12 months they were followed.

In a smaller study of 21 women, 13 of whom had breast cancer, participants also reported less trouble with sleeping, less fatigue, and less abnormal sweating after they started taking black cohosh, but this study did not use a placebo control group. This means that it was impossible to conclude whether the results were due to black cohosh or to a placebo effect.

A 2001 study of black cohosh and a placebo for breast cancer survivors found no difference in severity or number of hot flashes, although there was a slight reduction in sweating. About two-thirds of these patients were also taking tamoxifen, an anti-estrogen drug that is commonly used in the treatment of breast cancer. Two years later, another study of women with breast cancer being treated with tamoxifen found that hot flashes were less severe and occurred less often in women taking black cohosh. However, a 2006 study of 132 cancer survivors found no effect on hot flashes.

A large study done in 2010 had more than 35,000 post-menopausal women fill out a questionnaire regarding their long-term use of herbal supplements. Use of supplements commonly taken for menopausal symptoms, including black cohosh, was not linked with breast cancer risk in this study, but more long term research is needed.

Are there any possible problems or complications?

This product is sold as a dietary supplement in the United States. Unlike companies that produce drugs (which must be tested before being sold), the companies that make supplements are not required to prove to the Food and Drug Administration that their supplements are safe or effective, as long as they don't claim the supplements can prevent, treat, or cure any specific disease.
Some such products may not contain the amount of the herb or substance that is on the label, and some may include other substances (contaminants). Actual amounts per dose may vary between brands or even between different batches of the same brand. In 2007, the FDA wrote new rules to improve the quality of manufacturing for dietary supplements and the proper listing of supplement ingredients. But these rules do not address the safety of the ingredients or their effects on health.
Most such supplements have not been tested to find out if they interact with medicines, foods, or other herbs and supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Because of these limitations, any information on ill effects and interactions below should be considered incomplete.

Serious reactions to moderate doses of black cohosh are very uncommon. Side effects may include upset stomach, headache, rash, nausea, and vomiting. Very high doses may cause slow heart rate, uterine cramps, dizziness, tremors, joint pain, and light-headedness.

There have been reports of serious liver disease among women who had recently started using black cohosh. However, other studies have found no changes in liver function or liver blood flow in healthy women. Still, some doctors suggest that people who already have liver problems should not use this supplement. The U.S. Pharmacopeia (USP) advises that black cohosh products be labeled with the following statement: "Discontinue use and consult a healthcare practitioner if you have a liver disorder or develop symptoms of liver trouble, such as abdominal pain, dark urine, or jaundice."

Some doctors are concerned that taking black cohosh might affect how conventional cancer treatments work. There are conflicting results among studies of cancer cells grown in laboratory dishes. Black cohosh does not seem to have an impact on the effectiveness of radiation therapy in these cells, while the herb seems to make some chemotherapy drugs less effective and others more effective.

Some studies found black cohosh may reduce the growth of breast cancer cells in laboratory dishes, but another study suggested that it can increase the spread of breast cancer in mice. Because of these conflicting reports, until more is known about this issue, many oncologists recommend a cautious approach and suggest delaying use of black cohosh until breast cancer treatment is over. Some may recommend not using black cohosh until its effects on breast tissue are better understood.

Allergic reactions are possible but rarely reported. Those who are allergic to other members of the buttercup family may be more likely to react to black cohosh. The herb also contains small amounts of salicylic acid and should be used with caution by those allergic to aspirin.

Commission E (Germany’s regulatory agency for herbs) recommends that the herb not be taken for more than 6 months in a row. It should be used with caution in people with high blood pressure and those taking medicine for high blood pressure.

Women who are thinking about any form of hormone replacement therapy should consult their doctors before taking black cohosh. Women who are pregnant or breast-feeding should not use this herb. Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.

Additional resources

More information from your American Cancer Society

The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-227-2345).

Dietary Supplements: What Is Safe?

The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management

Complementary and Alternative Methods and Cancer

Placebo Effect

Learning About New Ways to Treat Cancer

Learning About New Ways to Prevent Cancer


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Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.

Last Medical Review: 06/27/2011
Last Revised: 06/27/2011