Black cohosh (Actaea racemosa) is a plant native to North America. Its root has been used for women’s health for centuries, and today it’s one of the best-selling supplements for hot flashes and night sweats.
How it might work
Early theories suggested black cohosh acted like estrogen. More recent research suggests it doesn’t have meaningful estrogen-like effects. Instead, it may act on serotonin and other pathways in the brain involved in temperature regulation. The mechanism isn’t settled.
What the research shows
The evidence is mixed:
- Some randomized trials have found reductions in hot flashes compared with placebo, particularly with standardized extracts.
- Others, including a large US trial and a 2012 Cochrane review, found no clear benefit over placebo across the studies pooled.
Part of the difficulty is that products vary widely in extract type, dose and quality, and the placebo effect for hot flashes is substantial — often a 20–30% reduction.
Many studies use standardized extracts with daily doses in the range of 20–40mg of extract (sometimes higher), standardized to triterpene glycosides. If you try it, choose a product that states both the dose and the standardization.
Safety
Black cohosh is generally well tolerated in studies lasting up to a year. Side effects can include stomach upset, headache and rash.
There have been rare reports of liver injury in people taking black cohosh. A direct link hasn’t been proven, but regulators in several countries require warnings. Stop taking it and see a doctor if you develop symptoms such as dark urine, yellowing of the skin or eyes, abdominal pain or unusual fatigue. Avoid it if you have liver disease.
Talk to your clinician first if you’ve had breast cancer or another hormone-sensitive condition, take other medications, or are pregnant.
The bottom line
Black cohosh is a reasonable option for some women who want a non-hormonal approach, provided they choose a quality product, give it a fair trial of around 8–12 weeks, and know the warning signs. Expectations should be modest.