Evening Primrose Oil
Rich in omega-6 fatty acids, evening primrose oil offers some unique health benefits.
Evening primrose (scientific name Oenothera biennis) is a North American medicinal plant found in the Onagraceae plant family. The seeds—seed oil in particular—are the plant part used in medicine due to their rich levels of the polyunsaturated fatty acid (PUFA) molecule gamma-linolenic acid (GLA) as well as linoleic acid.
GLA is used to treat several skin conditions, including skin inflammation, itch, and atopic dermatitis. Other medicinal uses include the treatment of rheumatic disorders, irritable bowel syndrome, and menopausal symptoms. Let’s look deeper at what scientists have found regarding the safety and efficacy of evening primrose oil.
Botanical Origins
Evening primrose has long been appreciated by Native American and First Nations peoples of North America, where it originates. It features bright yellow blooms that last from late spring to late summer, thereafter yielding capsule fruits containing numerous seeds. Today, it can be found growing on all continents with the exception of Antarctica. It thrives in disturbed soil sites. It was first introduced to Europe as a decorative plant in the 1700s, and more recently, the largest global producer of this plant as a crop is China, with a market share of 90%.
Medicinal History
All parts of the evening primrose plant, including the roots, have been used as food by indigenous North Americans. For example, the young greens are cooked and eaten. The bark and leaves have also been used for an assortment of maladies, including piles (hemorrhoids), gastrointestinal disorders, cough, and as a sedative.
Chemistry
Evening Primrose Oil (EPO) is rich in PUFAs, notably omega-6 fatty acids like linoleic acid (70-74%) and gamma-linolenic acid (GLA, 8-10%), as well as a smaller proportion of omega-9 fatty acids (e.g., oleic and palmitic acids, 6-7%). This unique fatty acid composition, with a higher ratio of mono- and polyunsaturated fatty acids compared to other oils, positions EPO as a valuable dietary supplement. GLA, a key constituent, is known for its anti-inflammatory properties and positive effects on various inflammatory diseases and cardiovascular health. In addition to fatty acids, EPO contains other health-relevant phytochemicals such as sterols and phenolic acids (caffeic, vanillic, gallic, and others), which contribute to its antioxidant, anticancer, and hormonal regulation properties.
Importantly, EPO is highly influenced by its growing environment, with factors like sunlight and soil affecting its oil yield and fatty acid composition, highlighting the need for comparative studies across different seed cultivars and geographical areas. Various extraction methods, including cold pressing and supercritical carbon dioxide extraction, affect the yield and quality of EPO, with ongoing research into optimizing these processes and extending oil shelf life through natural antioxidants.
Pharmacology
EPO has been subjected to many scientific studies to assess efficacy against a variety of pharmacological targets. It is available in various forms including liquid oil, capsules, pills, and topical and vaginal formulations, with examples like Efamol®, Efalex®, Epogam®, and Efanatal®. These products typically contain 8–10% gamma-linolenic acid (GLA), along with other fatty acids. The standard oral dosage of EPO for short-term use is around 6 grams per day, although there are no established guidelines for topical or vaginal dosages. Clinical studies have observed that GLA from EPO reaches its peak plasma level within 2.7 to 4.4 hours post ingestion, with absorption rates varying depending on the time of day. For more details, take a look at this 2023 review paper on the matter. Here, I summarize some of the major findings.
Antioxidant Activity
EPO is rich in antioxidants, primarily due to PUFAs and phenolic compounds like flavonoids and phenolic acids, which act as free radical scavengers and metal chelators.
Clinical studies, including one on women with gestational diabetes, have shown that EPO significantly improves antioxidant markers in the body, suggesting its potential benefit in reducing oxidative stress.
Anti-inflammatory Activity
EPO has been linked to mitigating various inflammatory diseases, such as multiple sclerosis, due to its high flavonoid content and the anti-inflammatory properties of GLA.
Clinical studies indicate EPO's effectiveness in reducing inflammation in conditions like ulcerative colitis by altering inflammatory mediators and enzyme activities within the body.
Lipid Metabolism, Diabetes, and Metabolic Syndrome
EPO has shown potential in reducing serum cholesterol and triglycerides, thereby aiding in the management of hyperlipidemia, a risk factor for cardiovascular diseases.
The oil's benefits extend to improving heart health in animal models, suggesting potential antiatherosclerosis effects, but further research is needed to confirm these effects in humans.
Antimicrobial Activity
EPO exhibits antimicrobial properties against both Gram-negative and Gram-positive bacteria, attributed to its components like essential fatty acids, sterols, and flavonoids.
Further research is needed to understand the exact mechanisms of EPO's antimicrobial action and its efficacy in human models.
Anti-osteoporosis Activity
EPO, especially when combined with fish oil, has been found to positively influence bone health markers in postmenopausal women, suggesting its potential in preventing osteoporosis.
The exact interactions between EPO and standard osteoporosis drugs remain to be explored for potential synergistic effects.
Safety and Potential for Drug Interactions
Adverse Effects
Studies on EPO report minor side effects like headache, nausea, indigestion, and gastrointestinal discomfort. In certain cases, notably in pregnant women and newborn infants, more severe reactions were observed.
Drug Interactions
EPO can interact negatively with several drugs. It may interfere with phenothiazines, increasing the risk of seizures, and can affect the efficacy of antiplatelet drugs and antiretrovirals, potentially leading to adverse reactions.
Contraindications
Due to its effects on blood clotting and seizure threshold, EPO should be avoided by individuals with bleeding disorders, epilepsy, seizure disorders, schizophrenia, and those about to undergo surgery.
Contamination Concerns
Commercial EPO products have been found to contain harmful environmental contaminants, including polycyclic aromatic hydrocarbons (PAHs), which exceed acceptable levels and pose risks like carcinogenesis and dysbiosis. This has led to calls for stricter regulation and risk mitigation efforts.
The Takeaway
EPO exhibits a range of pharmacological activities, such as anti-inflammatory, antioxidant, antimicrobial, and antiosteoporosis effects, attributed to its components like GLA, phenolic acids, and flavonoids. Ongoing research aims to fully understand and utilize these properties in food and pharmaceutical applications.
Yours in health, Dr. Quave
Cassandra L. Quave, Ph.D. is a scientist, author, speaker, podcast host, wife, mother, explorer, and professor at Emory University School of Medicine. She teaches college courses and leads a group of research scientists studying medicinal plants to find new life-saving drugs from nature. She hosts the Foodie Pharmacology podcast and writes the Nature’s Pharmacy newsletter to share the science behind natural medicines. To support her effort, consider a paid or founding subscription, with founding members receiving an autographed 1st edition hardcover copy of her book, The Plant Hunter.
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