What is black cohosh?
Black cohosh is a perennial plant that grows in North America and is most commonly used as a dietary supplement to relieve symptoms of menopause Symptoms Menopause is the permanent end of menstrual periods and thus of fertility. For up to several years before and just after menopause, estrogen levels fluctuate widely, periods become irregular... read more 
. Although it is used to produce estrogen-like effects, it does not contain any plant estrogens.
Its botanical name is Actaea racemosa, and it is also known as black bugbane and black snakeroot, among other names.
The underground stem of this plant is available in powder, tablet, or liquid form.
Black cohosh supplements should be manufactured to contain certain active ingredients, called triterpenes.
Black cohosh contains certain substances, such as a form of the active ingredient in aspirin, that provide anti-inflammatory effects.
What claims are made about black cohosh?
People most often take black cohosh for menopausal symptoms (such as hot flashes, night sweats, mood swings, rapid heart rate, and vaginal dryness). People sometimes take black cohosh to treat arthritis or to treat menstrual symptoms.
Does black cohosh work?
Scientific evidence regarding benefit in relieving menopausal symptoms is conflicting. Some studies show that black cohosh relieves menopausal symptoms somewhat but not as effectively as hormonal treatments. However, other studies found no difference between black cohosh and placebo Placebos Placebos are substances that are made to resemble drugs but do not contain an active drug. (See also Overview of Drugs.) A placebo is made to look exactly like a real drug but is made of an... read more (substances that do not contain an active ingredient) in relief of hot flashes or menopausal symptom scores. One difficulty is that the ingredients in black cohosh supplements are not standardized.
There are few reliable data on the effectiveness of black cohosh for other disorders and symptoms.
What are the possible side effects of black cohosh?
Side effects are uncommon. The most likely are headache and stomach discomfort.
Black cohosh may also cause dizziness, excessive sweating, and, in high doses, low blood pressure.
Because a few people have developed liver problems, the U.S. Pharmacopeia (USP) has recommended that black cohosh products be labeled with a warning that they may be toxic to the liver.
In pregnancy, black cohosh may theoretically cause uterine contractions and thus result in miscarriage. Also, it should be avoided while breastfeeding, because it is present in breast milk, possibly causing hormonal effects in nursing infants.
What drug interactions occur with black cohosh?
Black cohosh may lessen the effectiveness of the chemotherapy drugs tamoxifen and irinotecan.
Recommendations
Black cohosh may help alleviate menopausal symptoms, but any possible benefit is likely to be small. The North American Menopause Society does not recommend its use because the evidence supporting its use is of low quality. Conventional treatments (for example, hormonal treatments) have greater benefits.
Black cohosh appears to be reasonably safe, but it has been linked to some severe cases of liver damage, so it is not risk-free. People who are sensitive to aspirin or have a seizure disorder, liver disease, hormone-sensitive cancers (for example, certain kinds of breast cancer), stroke, or high blood pressure should not take black cohosh. Also, pregnant and breastfeeding women should avoid its use.
