Evening Primrose Oil vs Black Cohosh for Perimenopause: What Does the Evidence Say?
Evening primrose oil and black cohosh are popular supplements for perimenopause symptoms. Compare the evidence, uses, safety, and who each suits best.
Two popular supplements, different mechanisms
Evening primrose oil and black cohosh are among the most widely used natural supplements for perimenopause symptoms. Both are often marketed for hot flashes and hormonal discomfort, but they work through entirely different mechanisms, have different evidence bases, and suit different symptom profiles. Understanding what each does, and what it does not do, allows women to make a more informed decision about whether either is worth trying for their individual needs. Neither is a substitute for medical advice, and women with significant symptoms should discuss their options with a healthcare provider before relying on supplements alone.
What is evening primrose oil and how does it work
Evening primrose oil is extracted from the seeds of the Oenothera biennis plant and is rich in gamma-linolenic acid, an omega-6 fatty acid. Gamma-linolenic acid is a precursor to prostaglandins, compounds that regulate inflammation and a range of physiological processes. It is this anti-inflammatory and prostaglandin-modulating effect that is thought to underlie any benefits evening primrose oil may have for perimenopause symptoms. It does not contain or mimic estrogen. Evening primrose oil has been used for conditions including premenstrual syndrome, breast pain, and eczema, and some women use it for menopausal hot flashes. It is generally considered safe for most people when taken at recommended doses.
What is black cohosh and how does it work
Black cohosh is a plant native to North America whose root extract has been used for menopause symptoms for decades. It was originally thought to act as a phytoestrogen, meaning a plant compound that mimics estrogen in the body, but more recent research suggests its mechanism is different. Black cohosh appears to act primarily on serotonin receptors in the brain, which may explain its effects on hot flashes and mood. This is relevant for safety: because it does not appear to act as an estrogen, it is not thought to stimulate estrogen-sensitive tissue, which has implications for women with a history of estrogen-sensitive breast cancer, though this remains a cautious area and specialist advice is important.
The evidence for evening primrose oil
The clinical evidence for evening primrose oil for menopausal hot flashes is limited. Some small trials have suggested modest benefits for hot flash frequency and severity, but the studies are generally low quality, small in size, and inconsistent in their findings. A 2013 randomised controlled trial published in the journal Archives of Gynecology and Obstetrics found a modest reduction in hot flash severity with evening primrose oil compared with placebo, though the effect was not large. Evening primrose oil is more consistently supported for breast tenderness, with reasonable evidence that it reduces mastalgia, a symptom that many perimenopausal women experience. Its effect on other perimenopause symptoms such as anxiety, sleep, and vaginal dryness is not well established in trials.
The evidence for black cohosh
Black cohosh has been studied more extensively than evening primrose oil for hot flashes. A number of randomised controlled trials have found that standardised black cohosh extract reduces hot flash frequency and severity compared with placebo, and several systematic reviews have concluded that it is modestly effective, particularly for hot flashes and night sweats. The German regulatory authority Commission E has approved black cohosh for menopausal complaints including hot flashes, mood disturbance, and sleep disruption. Results across trials are not entirely consistent, with some large trials finding no significant effect compared with placebo, but the overall body of evidence is more supportive than for evening primrose oil.
Safety and cautions for each
Evening primrose oil is generally well tolerated. Side effects at standard doses are mild and may include nausea, digestive discomfort, or headaches. It should be used with caution in women taking blood-thinning medications because of its mild antiplatelet effects. Black cohosh has a more complex safety profile. Rare cases of liver toxicity have been reported in women using black cohosh supplements, though a causal relationship has been debated. Most experts regard the risk as very low when using standardised, reputable products at recommended doses for no longer than six months, but women with liver disease should avoid it. Women with hormone-sensitive conditions should discuss black cohosh specifically with their doctor before use.
Which to consider and when
If breast tenderness is a primary complaint alongside mild hot flashes, evening primrose oil is the supplement with the stronger evidence base for that specific symptom and may be worth trying. If hot flashes and night sweats are the dominant issue, black cohosh has a stronger, if still moderate, evidence base and has been more widely studied. Women who cannot or prefer not to use hormone therapy may find either supplement provides some benefit, with expectations calibrated to modest effects rather than the significant relief that estrogen therapy typically delivers. Tracking symptoms with PeriPlan before and during a trial period of any supplement helps you assess whether it is genuinely making a difference or whether the improvement is due to other factors.
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