Myth-check: does black cohosh help with hot flashes?

The claim. Black cohosh, a North American plant sold as capsules and tinctures, reduces hot flashes and night sweats. It is the most widely used herbal remedy for menopause and is often described as a natural alternative to hormone therapy.

The short answer. It might do a little for some women, but the best evidence does not show it working better than a placebo, and the placebo effect for hot flashes is large. If it helps you, that is real to you, and it is also what you would expect to see even if the capsules did nothing.

What the trials show

Hot flashes are unusually responsive to placebo. In trials of almost anything, the placebo group typically reports a 20 to 40 percent reduction in frequency. That means a product only “works” if it beats that figure, which is why anecdote and small open studies tell you little.

The larger, blinded trials of black cohosh have mostly failed to beat placebo:

• The Herbal Alternatives for Menopause (HALT) trial, a year-long randomized study with several arms, found that black cohosh alone, and in a multibotanical combination, was no better than placebo for hot flash frequency or severity. Hormone therapy, included as a comparison arm, was clearly better.
• A 2012 Cochrane review pooled 16 trials with more than 2,000 participants and concluded there was insufficient evidence to support using black cohosh for menopausal symptoms, with the caveat that the trials varied in quality, dose, and preparation, which makes pooling difficult.
• Some individual trials, particularly of one standardized German extract, have reported benefit. These tend to be shorter, smaller, or less rigorously blinded, and their results have not been consistently reproduced.

The honest reading is “probably not, but the trials are not uniform enough to say never.” That is what most guideline bodies conclude.

What the guidelines say

The Menopause Society’s 2023 position statement on non-hormone therapy reviewed the supplement evidence and did not recommend black cohosh for vasomotor symptoms. NICE guidance for the UK notes that there is some evidence black cohosh may relieve vasomotor symptoms but that its safety is uncertain, preparations vary, and it can interact with other medicines.

Safety

Black cohosh is well tolerated in trials, with stomach upset and headache the most common complaints. Two things deserve a mention:

1. Liver. There are case reports of liver injury in people taking black cohosh. A causal link has not been proven, and the reports are rare relative to the number of users, but regulators in several countries require or recommend a warning. If you have liver disease or take other medicines that affect the liver, mention it to a clinician before taking it.
2. Quality. Herbal supplements are not held to the same manufacturing standards as medicines in most countries. Studies that tested black cohosh products off the shelf have found some that contained other plants or very different amounts of active compounds than labeled.

So should you take it?

That is between you and a clinician who knows your history. What this post can say is:

• If you try it, give it a fair trial of six to eight weeks and count your hot flashes before and after, because your own impression over a few days is not reliable for a symptom this variable.
• If it does nothing after that, stop; there is no reason to expect a late effect.
• If you are getting hot flashes that disrupt your life, there are treatments with much stronger evidence, hormonal and non-hormonal, and the treatment options hub covers them.

Sources

1. Black cohosh (Cimicifuga spp.) for menopausal symptoms · Cochrane Database of Systematic Reviews, 2012
2. Treatment of vasomotor symptoms of menopause with black cohosh, multibotanicals, soy, hormone therapy, or placebo: a randomized trial (HALT) · Annals of Internal Medicine, 2006
3. The 2023 Nonhormone Therapy Position Statement of The North American Menopause Society · Menopause, 2023
4. Black Cohosh: Usefulness and Safety · National Center for Complementary and Integrative Health
5. Menopause: identification and management (NG23) · NICE, 2024