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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 symptoms on its own — women use it widely for this, but the provided evidence doesn't support it. No solid evidence it treats eczema in children as a standalone supplement. Not a replacement for standard diabetes medications. The anti-aging and skin-glow claims you see on product labels are not backed by the studies reviewed here.

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 and reduces need for medical induction.

Moderate Evidence

Effective at: 1000-2000 mg vaginally

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

Weak Evidence

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

Added to misoprostol vaginally, shortens fetal expulsion time and reduces pain during pregnancy termination.

Moderate Evidence

Effective at: 1000 mg vaginally every 4 hours (combined with misoprostol)

Absorption & Bioavailability

Unknown from provided studies — no pharmacokinetic data reported. Vaginal administration appears effective for local cervical effects. Oral GLA from EPO does appear to shift plasma fatty acid profiles based on one trial.

Red Flags to Watch For

  • Vaginal use during pregnancy should only be done under medical supervision — self-administering EPO to induce labor is risky without clinical oversight.
  • Most studies are small (under 50 participants per group), limiting confidence in results.
  • EPO is often combined with other supplements (e.g., fish oil) in trials, making it hard to isolate EPO's specific effects.
  • Long-term safety data is lacking — no studies in the provided evidence examined use beyond 12 weeks.
  • Over 1,000 registered supplement products exist, but formulations and GLA content vary widely — dose on the label may not reflect actual GLA delivered.

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