Black Cohosh: Uses & Side Effects

Black cohosh is a herbal root from the buttercup family that is currently being sold as a dietary supplement and remedy for symptoms of menopause.

About Black Cohosh

Black cohosh is a tall, flowering perennial of the buttercup family which grows in the woodland areas of the eastern United States and Canada. The stems and subterranean root of black cohosh have a long history as a traditional folk remedy for various ailments (mainly menopause and menstrual issues), and are currently also used as a dietary supplement.

Native Americans are often credited for discovering the alleged medicinal properties of black cohosh, and the American Cancer Society reports that cohosh is actually a Native American word meaning “knobby rough roots.” Apparently, the Native Americans introduced the usage of black cohosh to European colonists, and it was quickly assimilated into American culture as a 19th-century home remedy. In fact, according to a webpage devoted to the herb from New York University’s Langone Medical Center, black cohosh was the main ingredient in a very popular late nineteenth century elixir called Lydia E. Pinkham’s Vegetable Compound for menstrual cramps.

Since the 1950s, black cohosh has been widely used throughout Europe as a popular treatment for symptoms of menopause, premenstrual syndrome (PMS), and painful menstruation.

Black Cohosh is also sometimes called black snakeroot, macrotys, bugbane, bugwort, rattleroot, rattletop, rattleweed, squawroot, or Remifemin. The Mayo Clinic maintains a webpage containing an exhaustive list of additional alternate names and terms.

Black cohosh should not be confused with blue cohosh or white cohosh, as these are different plants with differing effects and toxicities.

Black Cohosh Uses

Among Native Americans and as a 19th-century folk medicine, black cohosh had a long list of traditional uses. When consulting this list of uses, one might get the impression that black cohosh was considered something of a cure-all. However, aside from current usage as a dietary supplement and as a treatment for menopausal and menstrual issues, black cohosh is no longer applied as a remedy for the majority of ailments for which it was once traditionally used. This is primarily because there is insufficient or nonexistent evidence that black cohosh actually alleviates the many ailments that tradition has assigned to it.

The following is a list of some menopausal and menstrual symptoms that are purportedly relieved by black cohosh:

• Hot flashes
• Night sweats
• Vaginal dryness
• Cramps
• Irritability
• Headaches
• Mood swings
• Sleep disturbances
• Heart palpitations
• Osteoporosis

Other Uses

In recent years, black cohosh has been included in some men’s supplements designed to enhance workouts and increase testosterone. Supplement vendors describe the inclusion of black cohosh as a means to inhibit the production of estrogen and aid in the absorption of other compounds. It is not clear if black cohosh has been tested for this indication, or if its effects have ever been studied in men.

The Science of Black Cohosh

It is not currently known exactly how black cohosh works, but it is thought that it may have characteristics similar to estrogen. However, it should not be considered a herbal estrogen alternative. A more accurate point of view is that it may perform similarly to estrogen in certain parts of the body for certain people.

A number of scientific studies on black cohosh have been carried out, and the results have been mixed. Most of the collective evidence suggesting that it relieves symptoms of menopause or menstruation has been described with words such as unclear, inconsistent, conflicted, and incomplete. Some optimistic experts have described black cohosh as possibly or modestly effective, while more skeptical experts agree that more research is required before any reliable conclusions can be deduced.

The National Institute of Health offers an online fact sheet for health professionals which provides comprehensive information on various clinical studies in relation to black cohosh. The page can be viewed here.

Black Cohosh Dosage, Interactions, and Warnings

Dosage – Daily use of black cohosh in the recommended dosage is currently thought to be possibly safe for periods of up to 6 months. The typical dosage for menopausal or menstrual symptoms is 20-80 mg tablets of a standardized extract one to two times each day. A daily dose of 1-2 grams of dried root powder or 10-40 drops of a tincture/extract (depending on potency) is considered the recommended equivalent. A daily dose in excess of 900 mg is considered to be an overdose.

Possible Interactions:

• Black cohosh may be toxic to the liver and combining with Atorvastatin/Lipitor might increase the possibility of liver damage
• Black cohosh may reduce the effectiveness of the chemotherapy drug Cisplatin
• Black cohosh may alter hormones and have certain estrogen-like properties. For this reason, it should be avoided in combination with birth control pills, hormone replacement therapy, or estrogen drugs such as tamoxifen and raloxifene
• Black cohosh may increase risk of bleeding when combined with aspirin, anticoagulants/blood thinners, anti-platelet drugs, and/or nonsteroidal anti-inflammatory drugs
• Black cohosh may decrease blood pressure and should be avoided in combination with blood pressure medications.
• A WebMD page devoted to black cohosh claims that it may interact negatively with sedatives

Since black cohosh might be toxic to the liver, it may negatively interact with a number of other drugs affecting the liver. It may also negatively interact with a number of other herbs and dietary supplements. Both WebMD and the Mayo Clinic provide lengthy and informative pages on these additional interactions with black cohosh.

Black Cohosh Should Be Avoided By:

Children under 18 – The effects of black cohosh have not been studied on children.

Pregnant and breast-feeding women – Black Cohosh may alter hormone levels and increase risk of premature labor and/or miscarriage. It is not currently known if black cohosh is transmitted through breast milk.

Women that have, have had, and/or are high risk for breast cancer – Scientific studies on black cohosh and breast cancer have had mixed results. According to the American Cancer Society, some studies appear to show that black cohosh inhibits the growth of breast cancer cells, while other studies have shown that black cohosh causes an increase of breast cancer cells in mice. Black Cohosh may also cause some chemotherapy drugs, such as Cisplatin, to be less effective.

Individuals with liver disease – There have been some reports of liver damage after using black cohosh. For this reason, black cohosh should not be used in combination with excessive amounts of alcohol or liver medications. The U.S. Pharmacopeia – “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.” WebMD also maintains a webpage from October of 2012 with a liver warning for black cohosh. In the UK, a similar warning was issued by the Medicines and Healthcare products Regulatory Agency (MHRA). The MHRA recommends that UK consumers only purchase black cohosh products that have been registered with the Traditional Herbal Registration (THR).

Women who have endometriosis, fibroids, ovarian cancer, uterine cancer, or other conditions that affect hormones – Black cohosh may alter some hormones and function somewhat like estrogen. The possibility exists that it could worsen these conditions.

Allergies – People with allergies to salicylic acid, aspirin, and plants of the Ranunculaceae/buttercup/crowfoot family should avoid taking black cohosh.

Protein S deficiency – People with a protein S deficiency should avoid black cohosh. It may increase the risk of blood clotting due to possible hormonal effects.

Black Cohosh Side Effects

It is uncommon for most people to experience severe reactions to a moderate dosage of black cohosh, and most side effects appear as a result of ingesting high doses.

The following are a collection of possible side effects from black cohosh usage:

• Stomach discomfort
• Nausea
• Headache
• Rash
• Heaviness in the legs
• Vomiting
• Vaginal spotting/bleeding
• Weight gain

The following are possible high dose side effects of black cohosh:

• Abdominal pain
• Slow heart rate
• Uterine cramping
• Dizziness
• Tremors
• Joint Pain
• Light-headedness
• Diarrhea
• Giddiness
• Visual dimness

A more inclusive listing of possible side effects is offered by the Mayo Clinic here.

Google Trends History

The Google Trends graph below shows interest in black cohosh over time. Interest in black cohosh appears to have peaked in July of 2004. Since then, interest has largely declined, yet still remains fairly consistent.

Bottom Line

Despite the history of black cohosh as a traditional herbal folk medicine for menopause, scientific studies regarding its effectiveness are mixed. Some experts claims that it is possibly effective while others maintain that the evidence is unclear and more studies need to be done. Although rare when used at the recommended dose, there are a number of possible interactions, warnings, and side effects that users of black cohosh need to be aware of. One growing concern is that black cohosh may be toxic to the liver and could possibly cause liver damage. Despite its inclusion in some male supplements, it does not appear that any major studies have been performed to bolster the claim that it may have any effect in men.

Updated March 11, 2015
Originally published August 2014