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Evening Primrose Oil

Also known as: EPO, Oenothera biennis oil, gamma-linolenic acid oil, GLA oil

Evidence under review. — Not yet rated

Plant oil rich in GLA. Shows promise for nerve pain, cervical ripening, and reducing inflammation.

  • What it does

    Evening primrose oil (EPO) is a plant-based oil pressed from the seeds of the Oenothera biennis plant. It is rich in gamma-linolenic acid (GLA), an omega-6 fatty acid with anti-inflammatory...

  • Evidence quality

    Evidence base hasn't been formally rated yet. See research below.

  • Clinical dose

    1000-2000 mg daily (oral or vaginal depending on use)

See full breakdown ↓ Methodology →

What the Science Says

Evening primrose oil (EPO) is a plant-based oil pressed from the seeds of the Oenothera biennis plant. It is rich in gamma-linolenic acid (GLA), an omega-6 fatty acid with anti-inflammatory properties. Clinical trials suggest it can reduce pain in diabetic nerve damage at 1000–2000 mg daily, support cervical ripening in late pregnancy when used vaginally, and help lower inflammatory markers like IL-6 when combined with fish oil during chemotherapy.

What It Doesn't Do

Not proven to relieve menopausal hot flashes on its own — women use it widely for this but the evidence is missing from clinical trials. No solid proof it clears eczema in children. Won't replace standard diabetes medications. Not a standalone cancer treatment.

Evidence-Based Benefits

Reduces pain scores in people with painful diabetic neuropathy at 1000–2000 mg daily.

Moderate Evidence

Effective at: 1000-2000 mg daily

Vaginal EPO improves cervical readiness for labor in low-risk term pregnancies.

Moderate Evidence

Effective at: 1000-2000 mg vaginally

Combined with misoprostol vaginally, EPO shortens fetal expulsion time and reduces pain during pregnancy termination.

Moderate Evidence

Effective at: 1000 mg vaginally

Combined with fish oil, EPO lowers IL-6 levels in breast cancer patients undergoing chemotherapy.

Weak Evidence

Effective at: 351 mg GLA (from EPO) combined with fish oil daily for 12 weeks

Absorption & Bioavailability

Moderate — GLA from EPO is absorbed and incorporated into plasma phospholipids, as shown by measurable changes in fatty acid profiles in clinical studies. Vaginal administration appears effective for local cervical effects.

Red Flags to Watch For

  • Vaginal use during pregnancy should only be done under medical supervision — it can accelerate labor
  • Combined with blood thinners or anticoagulants, GLA may increase bleeding risk
  • Most studies are small (under 50 participants per group), limiting confidence in results
  • Evidence for popular uses like menopause symptom relief and eczema is not well-supported by the provided clinical data
  • Animal and lab studies (pancreas protection, aldose reductase inhibition) have not been confirmed in human trials

Research Sources

  • PubMed
  • NIH DSLD

This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-05-25