Herbs (Global Traditional) · European
Evening Primrose (Oenothera biennis) (Oenothera biennis)
Strong Evidencebotanical
Hermetica Superfood Encyclopedia
Evening primrose oil contains 7-14% γ-linolenic acid (GLA), an omega-6 fatty acid that serves as a precursor to anti-inflammatory prostaglandins. The oil provides essential fatty acids that may support inflammatory balance through prostaglandin E1 synthesis pathways.
Evening primrose (Oenothera biennis L.) is a biennial herb native to North America and widespread in Europe, with seeds containing 14-17% oil obtained through pressing or extraction methods. The oil is a fixed vegetable oil rich in polyunsaturated fatty acids, primarily linoleic acid (~70%) and γ-linolenic acid (7-14%).
The research dossier reveals no human clinical trials, RCTs, or meta-analyses for evening primrose oil were found in the available sources. No PubMed PMIDs, study designs, sample sizes, or clinical outcomes are available to assess efficacy.
No clinically studied dosage ranges are available in the research for extracts, powder, or standardized forms. Consult a healthcare provider before starting any new supplement.
Seeds are the primary nutritional component. **Oil composition (from seeds, typically 15-25% oil by weight):** Linoleic acid (LA, 18:2 n-6): 65-80% of total fatty acids; γ-linolenic acid (GLA, 18:3 n-6): 7-14% of total fatty acids; oleic acid (18:1 n-9): 5-12%; palmitic acid (16:0): 6-10%; stearic acid (18:0): 1-3%. **Sterols:** Total phytosterol content ~1,800-2,500 mg/kg oil; β-sitosterol dominant at 90-94.6% of sterol fraction (~1,600-2,350 mg/kg oil); campesterol 3-5%; Δ5-avenasterol trace amounts. **Tocopherols (vitamin E):** Total tocopherols ~150-250 mg/kg oil; predominantly γ-tocopherol (~80-90% of total tocopherols, ~120-225 mg/kg); α-tocopherol ~10-30 mg/kg; δ-tocopherol trace. **Protein:** Seeds contain approximately 15-20% protein by dry weight; amino acid profile includes glutamic acid, aspartic acid, arginine, and leucine as predominant amino acids. **Fiber:** Seed meal (after oil extraction) contains ~30-40% dietary fiber. **Minerals (whole seed, approximate):** Calcium ~850-1,200 mg/kg; potassium ~6,000-8,000 mg/kg; magnesium ~3,000-4,500 mg/kg; phosphorus ~5,000-7,000 mg/kg; iron ~50-120 mg/kg; zinc ~30-60 mg/kg. **Polyphenols (leaves and aerial parts):** Ellagitannins (oenothein A and oenothein B are major compounds, ~2-8% dry weight in leaves); gallic acid derivatives; flavonoids including quercetin and kaempferol glycosides (~0.1-0.5% dry weight in leaves); catechins and epicatechins in minor quantities. **Roots (traditionally consumed as vegetable):** Starch-rich (~10-15% fresh weight); modest vitamin C content; low fat content (<1%). **Bioavailability notes:** GLA from evening primrose oil is well-absorbed orally (>90% absorption as triglyceride form); GLA is enzymatically converted to dihomo-γ-linolenic acid (DGLA) and subsequently to anti-inflammatory series-1 prostaglandins; γ-tocopherol has lower bioavailability than α-tocopherol (~10-30% relative absorption); polyphenolic ellagitannins (oenothein B) have limited oral bioavailability due to high molecular weight and are partially metabolized by gut microbiota to urolithins; phytosterol absorption is inherently low (~2-5%) but sufficient to compete with cholesterol absorption.
γ-linolenic acid from evening primrose oil converts to dihomo-γ-linolenic acid (DGLA), which then produces prostaglandin E1 (PGE1) through cyclooxygenase pathways. PGE1 exhibits anti-inflammatory properties by inhibiting inflammatory cytokine production and modulating immune cell activity. The oil also provides linoleic acid that supports cell membrane structure and function.
Current clinical evidence for evening primrose oil remains limited and mixed across various health conditions. Some small-scale studies have examined GLA supplementation for skin conditions and hormonal balance, but results have been inconsistent. Most health claims are based on traditional use spanning over 30 years rather than robust clinical trials. Larger, well-designed studies are needed to establish definitive therapeutic benefits for specific conditions.
Evening primrose oil is generally well-tolerated with mild side effects including nausea, stomach upset, and headache reported in some users. The supplement may increase bleeding risk when combined with anticoagulant medications like warfarin due to its effects on platelet function. Individuals with seizure disorders should use caution as some case reports suggest potential seizure threshold lowering. Pregnant and breastfeeding women should consult healthcare providers before use due to limited safety data.
