# Primrose (Oenothera biennis)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/primrose
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-03-20
**Evidence Score:** 2 / 10
**Category:** Native American
**Also Known As:** Oenothera biennis, Common Evening Primrose, EPO, Evening Star, King's Cure-all, Fever Plant, Night Willow-herb, Scabish

## Overview

Evening primrose oil (EPO), derived from Oenothera biennis seeds, is concentrated in gamma-linolenic acid (GLA), an omega-6 fatty acid that serves as a precursor to [anti-inflammatory](/ingredients/condition/inflammation) prostaglandin E1 (PGE1). GLA is converted via dihomo-gamma-linolenic acid (DGLA) to PGE1, which modulates inflammatory signaling and may support skin barrier function and [hormonal balance](/ingredients/condition/hormonal).

## Health Benefits

• Contains gamma-linolenic acid (GLA), a fatty acid believed to have [anti-inflammatory](/ingredients/condition/inflammation) properties, though evidence is not well-established. • Rich in linoleic acid, which is essential for maintaining healthy skin and cell membrane structure, but specific benefits in humans are not well-documented. • Used traditionally to reduce fatigue, although modern scientific evidence is lacking. • Potentially beneficial for skin conditions like eczema, based on its fatty acid profile, but lacks robust clinical evidence. • May support general wellness due to its nutrient content, yet no conclusive human studies are available.

## Mechanism of Action

GLA in evening primrose oil is desaturated and elongated to dihomo-gamma-linolenic acid (DGLA), which competitively inhibits arachidonic acid [metabolism](/ingredients/condition/weight-management) via cyclooxygenase (COX) enzymes, reducing synthesis of pro-inflammatory [prostaglandin](/ingredients/condition/inflammation) E2 (PGE2) and leukotriene B4 (LTB4). DGLA is also enzymatically converted to prostaglandin E1 (PGE1), which activates adenylyl cyclase, raises intracellular cAMP, and suppresses platelet aggregation and [T-cell](/ingredients/condition/immune-support)-mediated inflammation. Linoleic acid (LA), the predominant fatty acid in EPO at roughly 65–80% of total fat content, is incorporated into phospholipid membranes and converted to ceramides, reinforcing the epidermal skin barrier via lamellar body secretion.

## Clinical Summary

A randomized controlled trial of 58 women with cyclic mastalgia found 3g/day EPO over 6 months significantly reduced pain severity compared to placebo, though effect sizes were modest. For atopic dermatitis, a meta-analysis of 9 RCTs (n=311) showed marginal improvement in itch and scaling, but the European Medicines Agency concluded evidence remains insufficient for a formal indication. A double-blind crossover study in 27 patients with rheumatoid arthritis using 6g/day GLA for 6 months reported reduced joint tenderness scores by approximately 25%, though sample sizes limit generalizability. Evidence for menopausal hot flash reduction is mixed, with one RCT of 56 women showing no significant benefit over placebo at 500mg/day for 6 weeks.

## Nutritional Profile

Primrose (Oenothera biennis) nutritional composition varies by plant part. Seeds are the most studied: seed oil contains 65-80% linoleic acid (omega-6), 8-14% gamma-linolenic acid (GLA), 6-10% oleic acid, and 7-10% palmitic acid. Total fat content of seeds is approximately 14-30% by dry weight. Protein content in seeds ranges from 15-18% dry weight, containing essential amino acids including glutamic acid, arginine, and aspartic acid. Carbohydrates comprise approximately 35-40% of seed dry weight. Leaves contain moderate levels of vitamin C (estimated 20-40 mg/100g fresh weight), beta-carotene (precursor to vitamin A), and small amounts of B vitamins including riboflavin and niacin. Mineral content includes calcium (approximately 200-300 mg/100g dry weight in leaves), magnesium, potassium, and iron. The plant contains polyphenolic compounds including flavonoids (quercetin, kaempferol derivatives) and tannins in leaf tissue. Root tissue contains mucilaginous polysaccharides. Bioavailability note: GLA from evening primrose oil is reasonably well-absorbed when consumed with dietary fat; however, conversion efficiency to [anti-inflammatory](/ingredients/condition/inflammation) eicosanoids varies significantly among individuals based on enzymatic activity and competing dietary fatty acids.

## Dosage & Preparation

No clinically studied dosage ranges are available. Traditional uses imply variable dosing based on the oil's fatty acid content. Consult a healthcare provider before starting any new supplement.

## Safety & Drug Interactions

Evening primrose oil is generally well-tolerated at doses of 2–8g/day, with the most common adverse effects being mild gastrointestinal upset, nausea, and headache. It may lower the seizure threshold and is contraindicated in individuals with epilepsy or those taking phenothiazine antipsychotics such as chlorpromazine, as case reports suggest increased seizure risk. EPO has mild antiplatelet activity via PGE1 upregulation and should be used cautiously alongside anticoagulants such as warfarin or NSAIDs due to additive bleeding risk. Safety in pregnancy has not been established in controlled trials; one observational study linked prolonged oral EPO use in late pregnancy with increased risk of prolonged rupture of membranes, and its use is generally not recommended without medical supervision.

## Scientific Research

No specific clinical trials or meta-analyses have been identified for evening primrose oil, indicating a lack of substantial scientific evidence. PubMed searches reveal no PMIDs, underscoring the need for more rigorous research.

## Historical & Cultural Context

Evening primrose has been traditionally used by the Anishinaabe for its leaves in tea to aid in reducing fatigue. The plant is also historically consumed as food, with roots eaten like potatoes and leaves used in salads.

## Synergistic Combinations

Borage oil, fish oil, vitamin E, flaxseed oil, turmeric

## Frequently Asked Questions

### How much GLA does evening primrose oil actually contain?

Evening primrose oil typically contains 8–10% GLA (gamma-linolenic acid) by weight, alongside 65–80% linoleic acid. A standard 1000mg softgel therefore delivers approximately 80–100mg of GLA, meaning doses of 2–4g/day are commonly used in studies to achieve therapeutically relevant GLA intake of 160–400mg daily.

### Does evening primrose oil help with PMS symptoms?

Some evidence suggests EPO may reduce PMS-related breast tenderness (mastalgia) through GLA's conversion to prostaglandin E1, which modulates prolactin sensitivity in breast tissue. A 6-month RCT using 3g/day showed significant cyclical pain reduction, but evidence for broader PMS symptoms such as mood changes or bloating is limited and inconsistent across trials.

### Can evening primrose oil improve eczema or skin conditions?

EPO's linoleic acid supports ceramide synthesis and epidermal barrier repair, which is theoretically beneficial in atopic dermatitis where barrier dysfunction is central to pathology. However, a Cochrane-style meta-analysis found only marginal improvements in itch and scaling across 9 RCTs, and the effect was not consistently clinically significant, leading most dermatology bodies to consider the evidence insufficient to recommend EPO as a primary eczema treatment.

### Is evening primrose oil safe to take with blood thinners?

Evening primrose oil should be used cautiously alongside anticoagulants like warfarin, clopidogrel, or aspirin because GLA-derived prostaglandin E1 (PGE1) inhibits platelet aggregation and may potentiate bleeding risk. No large pharmacokinetic interaction studies have quantified the magnitude of this effect in humans, so patients on anticoagulation therapy should consult a healthcare provider before use and monitor INR levels if warfarin is co-administered.

### What is the difference between evening primrose oil and borage oil for GLA content?

Borage oil (Borago officinalis) contains significantly more GLA than evening primrose oil, delivering approximately 20–26% GLA by weight compared to EPO's 8–10%, making borage oil a more concentrated source for the same dosage volume. However, borage oil also contains unsaturated pyrrolizidine alkaloids (UPAs) in some preparations, which are potentially hepatotoxic, whereas evening primrose oil does not carry this concern, giving EPO a cleaner safety profile despite its lower GLA concentration.

### What is the recommended daily dosage of evening primrose oil for general wellness?

Standard dosages range from 1,000–3,000 mg daily, typically divided into 2–3 doses, though optimal amounts vary by individual health goals and product concentration. Most clinical studies have used dosages between 1,400–2,800 mg daily, but always follow product label instructions and consult a healthcare provider to determine what suits your needs. Quality and GLA concentration can vary significantly between brands, making consistency important for any potential benefits.

### Is evening primrose oil safe to use during pregnancy and breastfeeding?

Evening primrose oil is generally considered safe during pregnancy in standard doses, and some evidence suggests it may support labor outcomes, though research is limited. However, it is best to consult with a healthcare provider before use during pregnancy, as some sources recommend avoiding it in the first trimester. Safety during breastfeeding is less studied, so medical guidance is advisable before supplementing while nursing.

### How strong is the scientific evidence for evening primrose oil's health claims?

Evidence for evening primrose oil remains mixed and modest; while some studies show potential benefits for hormonal and skin-related concerns, many trials are small or have methodological limitations. The most researched claim—PMS symptom relief—shows inconsistent results across studies, and evidence for other traditional uses like fatigue reduction lacks robust clinical support. More high-quality, large-scale research is needed to definitively establish efficacy for most marketed uses.

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