Oenothera biennis · herb
Evidence tier: insufficient
Rich in GLA (gamma-linolenic acid), reduces PMS symptoms, supports hormonal balance, improves skin hydration, and benefits conditions linked to fatty acid imbalance
Gamma linolenic acid (GLA) is the constituent, and the theory is that supplemental GLA shifts fatty acid metabolism toward the anti inflammatory series 1 prostaglandins, correcting a supposed delta-6-desaturase deficiency in people with eczema. It is a clean, attractive hypothesis and it is the reason the ingredient exists. The mechanism is now essentially all that is left of it, because when the hypothesis was tested in 1,596 randomised participants it did not translate into any clinical benefit. A plausible mechanism that fails in the clinic is a refuted mechanism, not a supporting one.
Insufficient, and NCCIH says it in one sentence: 'There's not enough evidence to support the use of evening primrose oil for any health condition.' Not for any condition. Evening primrose oil is one of the most widely sold supplements in the world and it has been tested properly and it did not work. ECZEMA is the definitive result, and it is negative. The Cochrane review 'Oral evening primrose oil and borage oil for eczema' (Bamford et al. 2013, PMID 23633319) pooled 27 randomised controlled trials in 1,596 participants (19 of them on evening primrose oil) and concluded: 'Oral BO and EPO are not effective treatments for eczema.' Improvement matched placebo. Cochrane went further than a null finding and said 'further studies on EPO or BO for eczema would be hard to justify', which is the language of a closed question. BREAST PAIN, the other flagship claim, is also negative: NCCIH states 'Evening primrose oil is probably not more effective than a placebo for breast pain.' MENOPAUSE, PMS and RHEUMATOID ARTHRITIS: NCCIH says 'There's insufficient evidence to show whether evening primrose oil is helpful' for any of them. That is the entire commercial proposition of the ingredient, and every part of it is either refuted or unevidenced. On safety, NCCIH considers it 'probably safe for most adults when taken orally', with gastrointestinal upset the usual complaint. The seed's caution on anticoagulants and on phenothiazine antipsychotics with seizure risk is conventional and reasonable, but it is precaution, not a documented outcome.
2 to 4 g evening primrose oil (minimum 8% GLA) daily, ideally split into two doses with food.
Take 1 to 3g daily with food. Allow 3 to 6 months for full hormonal benefit. Store in the fridge after opening. GLA content varies by product, look for standardised GLA content (8 to 10%).
Onset: ~42 days
Generally well tolerated. Avoid high doses in pregnancy (especially third trimester), association with prolonged labour. May potentiate anticoagulants and NSAIDs. Well tolerated in lactation at standard doses.
Pregnancy: caution
Breastfeeding: safe
Native American peoples used evening primrose as food and for skin conditions. The oil's therapeutic use for PMS, eczema, and hormonal balance in the modern era is based on its unusually high gamma-linolenic acid (GLA) content, a fatty acid with documented anti inflammatory effects.
Active compounds: gamma-linolenic acid (GLA), linoleic acid
Remedies using Evening Primrose · Browse by body system · Check it against what you take
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.