Best known for treating inflammation, evening primrose oil (EPO) has been a popular supplement for centuries used to address a host of conditions, including acne, arthritis, bruises, eczema, rheumatoid arthritis, hemorrhoids, digestive problems, and menopausal and premenstrual symptoms. Though EPO is widely used for many conditions, there is little evidence to support using the supplement.
Evening primrose (Oenothera biennis) is a plant native to the Americas, Europe, and parts of Asia with yellow flowers that open at sunset. The plant has been valued for centuries to soothe skin inflammation and GI complaints. Native Americans used parts from the plant to treat bruises and wounds and as topical treatments for skin inflammation. As the “King’s cure-all,” EPO became a popular folk remedy in 17th century Europe. More recently, EPO capsules, soft gels, and lotions are advertised as supporting women’s health, boosting energy, and promoting healthy skin.
Is there a benefit?
Oil from the seeds of the flower contains a high concentration of omega-6 fatty acids. ã-linolenic acid (GLA), the active ingredient in the oil, is thought to provide anti-inflammatory benefits through direct action on immune cells and indirect effects on the synthesis of prostaglandins, cytokines, and cytokine mediators.
Most studies on EPO focus on evaluating treatment for atopic dermatitis or breast pain. A 2013 review by Bamford and colleagues published in Cochrane Database Systemic Reviews studied EPO and borage oil for eczema. The authors assessed 27 studies including 1,596 participants. Their results revealed that EPO failed to significantly increase improvement of eczema symptoms compared to placebo.
Breast pain in premenopausal women is common and it is thought that saturated fatty acid esters may cause mastalgia when circulating hormones induce hypersensitivity in breast epithelium. EPO may restore the balance between saturated and unsaturated fatty acids, decreasing sensitivity to steroidal hormones or prolactin.
A 2021 systematic review and meta-analysis in the International Journal of Environmental Research and Public Health by Adni and colleagues reviewed 13 trials and over 1,752 randomized patients. Results revealed that EPO has no significant difference in breast pain reduction or relief compared with placebo or other treatments. The authors wrote that current evidence is insufficient to recommend EPO for the treatments of atopic dermatitis, menopausal or premenstrual symptoms, diabetic neuropathy, or rheumatoid arthritis.
While consistent reports in the literature claim benefits from EPO for atopic dermatitis, psoriasis, asthma, and mastalgia, there is no significant data to prove the effectiveness of EPO for most clinical indications. Quality data are lacking and most published trials have methodologic limitations.
EPO is generally obtained from cold pressing or solvent extraction from the seeds of the plant. Preparations are available as a topical moisturizing oil or capsules sold in 500 mg, 1,000 mg, and 1,300 mg dosages. In clinical trials evaluating atopic dermatitis, adult oral dosing ranged from 0.16 g to 0.64 g GLA per day, for 6 months.
What to tell your patients
While there is insufficient evidence to support the use of EPO for any health condition, EPO is considered safe and well-tolerated when taken in doses less than 6 g daily for up to a year.
Mild adverse effects may include upset stomach, nausea, diarrhea, and headache. Although EPO is considered safe for pregnant patients, taking EPO during the last weeks of pregnancy may delay labor. ■