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Limited evidenceWomen's health

Black Cohosh

Despite decades of use for hot flushes, the pooled randomized evidence does not show black cohosh beats placebo. It is one of the clearest examples of a bestselling menopause supplement whose trial record does not support the marketing.

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What the science says

  • Reduces menopausal hot flushes Limited evidence

    The Cochrane review pooled 16 randomized trials in 2,027 peri- and postmenopausal women and found no significant difference between black cohosh and placebo in hot flush frequency (mean difference 0.07 flushes/day, 95% CI -0.43 to 0.56) or in menopausal symptom scores. Trials ranged from 8 to 52 weeks at roughly 40 mg/day of standardized extract. The reviewers rated the evidence insufficient and called for better-conducted trials — which have not since overturned the null result.

  • Works through estrogen receptors Limited evidence

    Older marketing framed black cohosh as a phytoestrogen, but human trials consistently show no meaningful change in FSH, LH, estradiol, vaginal cytology or endometrial thickness. Whatever mechanism exists is more likely serotonergic or dopaminergic, and the absence of estrogenic action means it should not be assumed to carry hormone-therapy-like benefits for bone or vaginal atrophy.

  • Causes liver injury Limited evidence

    A meta-analysis of randomized trials of the isopropanolic extract found no signal of hepatotoxicity in pooled liver enzyme data across trial participants. However, dozens of spontaneous case reports of hepatitis and liver failure prompted label warnings from the EMA, the UK MHRA and Australia's TGA. The most likely reading is that idiosyncratic liver injury is rare but real, and product misidentification or adulteration with related Actaea/Cimicifuga species may explain part of it.

Dosage & safety

Studied doseTrials almost universally used 40 mg/day of standardized rhizome extract (commonly the isopropanolic extract, 20 mg twice daily or 40 mg once daily), for 8-52 weeks. Higher doses have not shown better results. Given the null pooled evidence, there is no dose that can be recommended with confidence for symptom relief.
SafetyCommon side effects are mild: GI upset, rash, headache, and occasional weight gain. The important issue is hepatotoxicity — case reports of autoimmune-like hepatitis and acute liver failure led European and Australian regulators to require liver-warning labelling. Stop immediately and seek care for jaundice, dark urine, or right upper quadrant pain. Do not use with existing liver disease or alongside other hepatotoxic agents. Data in women with a history of breast cancer are limited and reassuring but not definitive; discuss with an oncologist, particularly on tamoxifen. Avoid in pregnancy and breastfeeding. Species adulteration is common in the supply chain, so buy from suppliers who document botanical identity.

How to take it

Timing40 mg once daily or 20 mg twice daily; timing within the day does not matter.
With food?With food to reduce stomach upset.
Worth knowingSpecies adulteration is common, so buy from a supplier that documents botanical identity — and get liver enzymes checked if you use it beyond a few months.

Interactions

With medications

  • hepatotoxic drugs (methotrexate, isoniazid, some antifungals)

    Black cohosh has case reports of autoimmune-like hepatitis and acute liver failure, so risks compound. do not combine; stop immediately for jaundice, dark urine or right upper abdominal pain

  • tamoxifen

    Endocrine activity is unresolved and data in breast cancer survivors are limited. do not use without oncology sign-off

With other supplements

  • kava, green tea extract and butterbur

    Additive risk of drug-induced liver injury. do not stack hepatotoxic botanicals

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does black cohosh work for hot flashes?

The pooled evidence says no: a Cochrane review of 16 trials in 2,027 women found black cohosh no better than placebo for hot flush frequency or menopausal symptom scores. The evidence for black cohosh is limited.

Is black cohosh bad for your liver?

Liver injury from black cohosh appears rare but real: case reports of hepatitis and liver failure led EU, UK and Australian regulators to require liver warnings. Stop immediately and seek care for jaundice, dark urine or right upper abdominal pain.

Is black cohosh a phytoestrogen?

No — human trials show black cohosh does not meaningfully change FSH, LH, estradiol or endometrial thickness. So black cohosh should not be assumed to give hormone-therapy-like benefits for bone or vaginal atrophy.

What dose of black cohosh was studied?

Trials used 40 mg/day of standardised black cohosh extract, as 20 mg twice daily or 40 mg once, for 8-52 weeks. Given the null pooled results, no black cohosh dose can be recommended with confidence.

Scientific references

Where to buy

Vital Nutrients, Black Cohosh Extract, 60 Vegan Capsules (250 mg per Capsule)

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