# Cold-Pressed Evening Primrose Oil (Oenothera biennis)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/cold-pressed-evening-primrose-oil
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-03-31
**Evidence Score:** 2 / 10
**Category:** Seed Oils
**Also Known As:** Oenothera biennis oil, EPO, Evening primrose seed oil, Common evening primrose oil, German rampion oil, King's cure-all oil, Fever plant oil, Night willow-herb oil, Sundrop oil, Oenothera oil

## Overview

Cold-pressed evening primrose oil is derived from Oenothera biennis seeds and is rich in gamma-linolenic acid (GLA, 8.9–9.7%) and tocopherols (~770 mg/kg). GLA serves as a direct precursor to dihomo-gamma-linolenic acid (DGLA), which competes with arachidonic acid in eicosanoid synthesis to modulate [inflammatory](/ingredients/condition/inflammation) signaling.

## Health Benefits

• No specific health benefits can be confirmed from clinical trials as the research dossier contains no human clinical studies, RCTs, or meta-analyses
• Contains γ-linolenic acid (8.9-9.7%), a precursor to [anti-inflammatory](/ingredients/condition/inflammation) compounds, though no clinical evidence provided
• Rich in tocopherols (770 ppm, mainly gamma-tocopherol) with [antioxidant](/ingredients/condition/antioxidant) properties, but lacks clinical validation
• Contains phytosterols including beta-sitosterol (~9000 ppm), though no clinical outcomes documented
• May influence arachidonic acid pathways via phospholipase A2 and C mechanisms, but this is theoretical without clinical support

## Mechanism of Action

GLA from evening primrose oil is elongated by delta-6-desaturase to dihomo-gamma-linolenic acid (DGLA), which is converted by COX enzymes into 1-series prostaglandins (e.g., PGE1) that exert [anti-inflammatory](/ingredients/condition/inflammation) and vasodilatory effects. DGLA also competitively inhibits the conversion of arachidonic acid to pro-inflammatory 2-series prostaglandins and 4-series leukotrienes via COX-2 and 5-LOX pathways. Additionally, tocopherols in the oil act as lipid-soluble antioxidants, quenching peroxyl radicals and protecting polyunsaturated fatty acids from [lipid peroxidation](/ingredients/condition/antioxidant) within cell membranes.

## Clinical Summary

The current research dossier for cold-pressed evening primrose oil contains no human clinical trials, randomized controlled trials, or meta-analyses specific to this cold-pressed form, limiting the ability to confirm efficacy for any health outcome. Conventional (non-cold-pressed) evening primrose oil has been studied in small RCTs for conditions such as atopic dermatitis, premenstrual syndrome, and mastalgia, with mixed and generally modest results. A 2013 Cochrane review on evening primrose oil for eczema found insufficient evidence to support its use, citing poor trial quality and small sample sizes. Due to the absence of dossier-specific clinical data, any health claims for this ingredient remain mechanistically plausible but clinically unverified.

## Nutritional Profile

Cold-pressed evening primrose oil is composed almost entirely of lipids (~99-99.5% total fat), with no meaningful protein, carbohydrate, or fiber content. Fatty acid composition (per 100g oil): linoleic acid (omega-6, LA) ~65-80%, γ-linolenic acid (GLA, omega-6) ~8-10% (typically 8.9-9.7% per dossier data), oleic acid (omega-9) ~6-10%, palmitic acid (saturated) ~5-7%, stearic acid (saturated) ~1-3%, α-linolenic acid (omega-3) trace amounts <0.5%. GLA is the principal bioactive fatty acid, serving as a direct precursor to dihomo-γ-linolenic acid (DGLA) and subsequently to [prostaglandin](/ingredients/condition/inflammation) E1 (PGE1), bypassing the rate-limiting delta-6-desaturase enzyme step. Micronutrient content: tocopherols ~770 ppm total (predominantly gamma-tocopherol ~600-650 ppm, with minor alpha-, beta-, and delta-tocopherol fractions), contributing [antioxidant activity](/ingredients/condition/antioxidant) and oxidative stability to the oil. Phytosterols present at approximately 300-500 mg/100g, primarily beta-sitosterol. Polyphenols present in trace quantities. Energy density approximately 884 kcal/100g (9 kcal/g fat). Bioavailability notes: GLA from evening primrose oil is well-absorbed via lymphatic chylomicron transport; bioavailability is enhanced when consumed with meals containing other fats. Cold-pressing preserves tocopherol and GLA integrity versus solvent extraction or high-heat processing. Oil is highly susceptible to oxidative rancidity due to high polyunsaturated fat content; nitrogen-flushed, dark glass packaging is required to maintain potency.

## Dosage & Preparation

No clinically studied dosage ranges, forms, or standardization details are reported in the available research. Consult a healthcare provider before starting any new supplement.

## Safety & Drug Interactions

Evening primrose oil is generally well tolerated at typical doses of 2–8 g/day, with the most common adverse effects being mild gastrointestinal symptoms such as nausea, loose stools, and bloating. It may lower the seizure threshold and is contraindicated in individuals with epilepsy or those taking phenothiazine antipsychotics such as chlorpromazine. Due to its [prostaglandin](/ingredients/condition/inflammation)-modulating effects, caution is warranted with anticoagulants like warfarin, as GLA-derived PGE1 may inhibit platelet aggregation and increase bleeding risk. Safety data in pregnancy is insufficient; use during pregnancy or lactation should be avoided unless supervised by a healthcare provider.

## Scientific Research

The research dossier explicitly states that search results provide no specific human clinical trials, RCTs, or meta-analyses for cold-pressed evening primrose oil. No PubMed PMIDs or details on study designs, sample sizes, or clinical outcomes are available in the provided sources.

## Historical & Cultural Context

The research dossier provides no information on historical context, traditional medicine systems, indications, or duration of use for evening primrose oil.

## Synergistic Combinations

Other gamma-linolenic acid sources, omega-3 fatty acids, vitamin E, [antioxidant](/ingredients/condition/antioxidant) compounds, [anti-inflammatory](/ingredients/condition/inflammation) herbs

## Frequently Asked Questions

### How much GLA does evening primrose oil contain compared to other seed oils?

Cold-pressed evening primrose oil contains 8.9–9.7% gamma-linolenic acid (GLA), making it one of the more concentrated botanical sources of this omega-6 fatty acid. By comparison, borage oil contains approximately 20–26% GLA and blackcurrant seed oil contains roughly 15–19%, meaning evening primrose oil delivers a moderate but meaningful GLA dose per gram of oil consumed.

### What is the difference between cold-pressed and standard evening primrose oil?

Cold-pressing extracts oil from Oenothera biennis seeds using mechanical pressure at temperatures below approximately 49°C (120°F), which preserves heat-sensitive compounds such as tocopherols and prevents oxidation of polyunsaturated fatty acids like GLA. Conventional solvent-extracted or high-heat expeller-pressed oils may have reduced tocopherol content and higher levels of lipid oxidation byproducts, potentially affecting both potency and safety of the final product.

### Can evening primrose oil help with hormonal acne or PMS symptoms?

The proposed mechanism involves GLA conversion to PGE1, a prostaglandin that may reduce prolactin sensitivity and modulate cyclooxygenase-driven inflammation associated with PMS and hormonal skin changes. However, clinical evidence specifically for these outcomes is limited and inconsistent; small trials have not reliably demonstrated statistically significant benefits over placebo, and no large-scale RCTs currently confirm efficacy for hormonal acne or PMS using cold-pressed evening primrose oil.

### Does evening primrose oil interact with blood thinners like warfarin?

Yes, a potential pharmacodynamic interaction exists between evening primrose oil and anticoagulants such as warfarin. GLA-derived prostaglandin E1 (PGE1) inhibits ADP-induced platelet aggregation, which could additively increase bleeding risk when combined with warfarin, aspirin, or other antiplatelet drugs. Individuals on anticoagulant therapy should consult a physician before supplementing with evening primrose oil, as INR monitoring adjustments may be necessary.

### What tocopherol content does cold-pressed evening primrose oil provide and why does it matter?

Cold-pressed evening primrose oil contains approximately 770 mg/kg of tocopherols, primarily gamma-tocopherol, which function as endogenous antioxidants within the oil matrix. These tocopherols protect the highly unsaturated GLA from peroxidation during storage and after ingestion, preserving bioactivity; they also contribute independent antioxidant activity in cell membranes by neutralizing lipid peroxyl radicals and reducing formation of 4-hydroxynonenal (4-HNE), a cytotoxic oxidation byproduct.

### Is cold-pressed evening primrose oil safe to take during pregnancy and breastfeeding?

Evening primrose oil has been studied for potential benefits during pregnancy and postpartum, but safety data during pregnancy remains limited and conflicting in the research literature. It is generally recommended to consult with a healthcare provider before using evening primrose oil supplements during pregnancy or while breastfeeding. Some practitioners suggest it may be considered in the third trimester under medical supervision, but this should never be done without professional guidance.

### What is the recommended daily dosage of cold-pressed evening primrose oil for general use?

Common supplement dosages range from 1,000–3,000 mg daily, typically divided into doses with meals to support absorption, though optimal dosing has not been established through rigorous clinical trials. The appropriate dose may vary depending on individual health status, medications, and the specific health goal. It is advisable to start at a lower dose and consult a healthcare provider to determine the right amount for your needs.

### How does the quality and potency of cold-pressed evening primrose oil vary between suppliers?

Cold-pressed evening primrose oil quality varies significantly based on seed source, extraction methods, storage conditions, and oxidation levels, which affect GLA and tocopherol retention. Third-party testing for peroxide value, GLA concentration, and contaminants is not universally required, so products with verified certificates of analysis offer greater transparency than those without. Oils stored in opaque, refrigerated packaging tend to maintain higher antioxidant content than those exposed to light and heat.

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*Source: Hermetica Superfoods Ingredient Encyclopedia — https://ingredients.hermeticasuperfoods.com*
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