What they are: Evening primrose (Oenothera biennis), a yellow wildflower, yields an oil that is a popular supplement, usually sold as capsules. Borage oil, a similar product, is derived from the seed of a plant (Borago officinalis) known variously as bee plant or starflower. The oil of both plants is rich in gammalinolenic acid, which has many effects in the body, such as controlling inflammation.
Claims, purported benefits: Evening primrose oil and borage oil are said to be good for practically everything: eczema and nearly any kind of dermatitis or rash, rheumatoid arthritis, breast pain, breast cancer as well as other cancers, diabetes and the nerve damage it can cause, heart disease, symptoms of menopause, infertility, irritable bowel syndrome, hangovers, dry eye, premenstrual syndrome (PMS), and high cholesterol.
What the science says: Evening primrose oil and borage oil and the fats they contain have been much studied. The great majority of studies, unfortunately, have been of poor quality, but a few have been well designed and have been published in peerreviewed journals.
Skin conditions. The Natural Standard, which reviews complementary/alternative therapies, has concluded that there is fair evidence for the use of these oils (notably borage) in treating eczema and dermatitis. However, a 2010 review in the journal Nutrition found that five studies reported that borage oil was effective against atopic dermatitis, but another five did not. And a 2013 review by the Cochrane Collaboration evaluated 27 studies testing these oils for the treatment of eczema in 1,600 adults and children for up to 24 weeks. It concluded that the oils work no better than a placebo and that further studies “would be hard to justify.”
Hot flashes and other menopausal symptoms. Two reviews of research on herbal and other alternative treatments for menopausal symptoms (one in the Annals of Internal Medicine, the other in the Annals of Pharmacotherapy) found no benefit for evening primrose oil. The Natural Standard rated it as “D,” meaning there is “fair evidence against its use.” It has not been shown to be effective against PMS. In a 2010 study from the Mayo Clinic, women with premenstrual breast pain or tenderness who took evening primrose oil, vitamin E, or both did not benefit.
Rheumatoid arthritis. Some small studies have suggested benefits, but overall the evidence is inconsistent. A 2011 review of herbal therapies for rheumatoid arthritis by the Cochrane Collaboration concluded that evening primrose or borage oil may help reduce pain and improve function, but “adequate dose and duration of treatment are unknown.” The Arthritis Foundation and some doctors recommend evening primrose or borage oil on the “can’thurtmighthelp” theory.
Diabetes and diabetic nerve damage. Some studies (mostly in the lab or in animals) suggest that evening primrose oil might be helpful. But a comprehensive review of studies in the Journal of the American Board of Family Practice found that evening primrose oil (or similar supplements) is not effective for treating nerve damage caused by diabetes, and that drug interactions and side effects are possible.
Side effects: Potential side effects include stomach upset, nausea (less likely when taken with food), rashes, and headaches. Evening primrose oil has an anticlotting effect and thus may interact with certain anticlotting drugs, increasing the risk of bleeding. Borage oil, if not processed correctly, can contain substances that may be toxic to the liver over time.
Our advice: Evening primrose oil and borage oil are cheap, but an inexpensive supplement that does you no good and can cause side effects is not so cheap after all. And it may keep people with serious diseases from getting the medical treatment they need.