Black Cohosh for Menopausal Symptoms
Black cohosh is the most commonly used herbal supplement for menopausal symptoms, but current evidence does not support its effectiveness, with randomized trials showing no significant benefit over placebo for hot flashes or other vasomotor symptoms. 1, 2
Evidence Against Efficacy
The highest quality evidence demonstrates that black cohosh lacks clinical benefit:
A Cochrane systematic review of 16 randomized controlled trials (2027 women) found no significant difference between black cohosh and placebo for hot flush frequency (mean difference 0.07 flushes per day; 95% CI -0.43 to 0.56) or menopausal symptom scores. 3
Randomized trials specifically in breast cancer survivors show no benefit from black cohosh for treating hot flashes, which is particularly relevant given this population's need for non-hormonal alternatives. 1, 2
The National Comprehensive Cancer Network guidelines note that while limited data suggest possible benefit in the general population, randomized trials in breast cancer survivors demonstrate no benefit. 2
Dosing and Duration (If Used Despite Limited Evidence)
For patients who insist on trying black cohosh despite the lack of evidence:
- The standardized dose is 40-80 mg per day of black cohosh extract. 1, 4
- At least 4-12 weeks of treatment may be required before any potential therapeutic benefits become apparent. 4
- Most studies used a median daily dose of 40 mg for a mean duration of 23 weeks. 3
Safety Profile and Adverse Effects
Black cohosh has a relatively benign side effect profile but is not without concerns:
- Common adverse reactions include nausea, vomiting, headaches, dizziness, mastalgia, and weight gain. 4, 5
- A few cases of hepatotoxicity have been reported, though a direct causal relationship has not been definitively established. 5
- Black cohosh should not be administered to children or during pregnancy and lactation due to potential effects on sex hormones. 4
Superior Alternatives with Proven Efficacy
Rather than black cohosh, evidence-based first-line treatments include:
- Gabapentin 900 mg/day reduces hot flash severity by 46% compared to 15% with placebo, with efficacy equivalent to estrogen and no known drug interactions. 1
- Venlafaxine 37.5-75 mg daily reduces hot flash scores by 37-61%, with 68% of patients preferring it over gabapentin despite similar efficacy. 1
- Paroxetine 7.5-20 mg daily reduces hot flash frequency by 62-65%, though it should be avoided in women taking tamoxifen due to CYP2D6 inhibition. 1
Other Herbal Supplements with Limited Evidence
Vitamin E (800 IU daily) shows limited efficacy for mild vasomotor symptoms, but doses >400 IU/day are linked to increased all-cause mortality. 1, 2
Soy isoflavones demonstrate only modest improvement in hot flashes, with most benefits disappearing after 6 weeks of treatment in a review of 11 clinical trials. 2
Critical Clinical Caveat
The observed placebo effect in hot flash treatment is considerable, typically 25% or more, which may explain why some women report subjective benefit from black cohosh despite objective evidence showing no superiority to placebo. 6 This substantial placebo response should be discussed with patients when counseling about herbal supplements.