Black Cohosh for Hot Flashes

Key takeaways

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  Some studies show black cohosh is effective for hot flashes, but others show it’s no more effective than a placebo.

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  A few small studies have shown that black cohosh may reduce the risk of breast cancer — and recurrence — but more research is needed.

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  Black cohosh is generally safe to use, but can cause serious problems for people with liver disease.

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  Black cohosh may also interfere with some breast cancer treatments, so it’s important to talk to your doctor before you start taking it.

Black cohosh (Actaea racemosa) is a native North American flowering plant that was traditionally used to treat conditions ranging from fever to irregular periods. But today, some people take black cohosh supplements to reduce hot flashes. 

Though there is some evidence that black cohosh may reduce the risk of developing breast cancer and prevent recurrence, the studies done so far have been small.  There’s also some concern about black cohosh causing liver toxicity and poor quality control of the supplements.

Black cohosh is also known as black bugbane, black snakeroot, fairy candle, macrotys, rattletop, and rheumatism weed.

Black cohosh supplements, typically from the plant’s roots and stems, are available in powdered, liquid, and pill form. One popular black cohosh supplement is a pill with the brand name Remifemin. 

The research on black cohosh’s effect on breast cancer risk and efficacy in reducing hot flashes is mixed, and more studies are needed. 

Hot flashes

More research is needed to determine how effective black cohosh is for hot flashes. One small 2006 clinical trial in women with breast cancer showed that black cohosh gave no more relief from hot flashes than a placebo (sugar pill). Another small study in 2021 showed that black cohosh was not significantly more effective for women — more than half of whom were on tamoxifen — than a placebo. 

However, a 2003 study on breast cancer survivors in treatment-induced menopause showed that taking black cohosh along with Tamoxifen reduced the number and severity of hot flashes they had, and a 2019 study showed the same.  

Some studies suggest that black cohosh may act as a phytoestrogen — an estrogen-like compound found in plants — which may block estrogen’s actions in some tissues.

Breast cancer risk

A small 2007 study investigated the relationship between black cohosh use and breast cancer risk. The study found that women who took black cohosh were about 60% less likely to develop breast cancer than women who didn't take black cohosh. But it showed that black cohosh was associated with a lower risk — not necessarily that it reduced risk.

Another study found that people with a history of breast cancer who used Remifemin or Remifemin Plus had a significantly lower risk of recurrence, even when receiving tamoxifen.

Black cohosh is generally safe to use, and side effects are typically mild. They include upset stomach, rash, muscle pain, breast pain/enlargement, and spotting. 

However, in some people, black cohosh may cause serious side effects, such as liver damage. You shouldn’t take black cohosh if you have liver disease or are taking medications that may also affect liver function.

In addition, black cohosh may interfere with some cancer treatments. Some lab studies have found that black cohosh might increase the toxicity of some chemotherapy drugs, including Adriamycin and Taxotere. 

Since the research is mixed, it’s not clear whether black cohosh will help treat hot flashes in women with breast cancer. And since it may interfere with some treatments, doctors don’t usually recommend it for people with breast cancer.

And while the studies on black cohosh and breast cancer risk are encouraging, more studies are needed.

If you’ve been diagnosed with breast cancer or are at high risk for breast cancer, talk to your doctor before taking black cohosh supplements. There are other natural remedies for hot flashes that you can discuss, too.