Evening primrose (Oenothera biennis) is a wildflower whose seeds contain oil rich in linoleic acid and gamma-linolenic acid (GLA)—fatty acids involved in the production of prostaglandins, hormone-like substances that influence inflammation and other body functions.

Essential Fatty Acids and PMS

Research published in the Journal of Nutritional Medicine (1991;2:259–264) and the American Journal of Obstetrics and Gynecology (1984;150:363–366) reported that women with PMS often have lower levels of linoleic acid and GLA. These levels tended to improve with evening primrose oil supplementation.

A review in the Journal of the American Pharmaceutical Association (2000;40(2):234–242) summarized several studies of EPO for PMS:

  • Open-label (non–placebo controlled) studies found improvement in PMS symptoms.

  • Double-blind, placebo-controlled trials showed mixed results, with the most consistent benefit seen in cyclical breast tenderness.

The reviewer, Mary Hardy, MD, noted that while evidence is not conclusive, evening primrose oil is considered safe and may be reasonable to try for patients experiencing cyclical breast pain.

A Broader Nutritional Approach

EPO is often discussed as a source of GLA, but natural healthcare approaches usually look beyond a single nutrient. Because fatty acid metabolism can be influenced by diet and lifestyle, practitioners may also consider:

  • Reducing processed fats, refined sugar, and other foods that interfere with essential fatty-acid pathways

  • Ensuring nutrients that support prostaglandin balance, such as vitamin B6 and magnesium

  • Encouraging movement, hydration, and other supportive habits

These lifestyle factors work alongside essential fatty acids to support overall balance rather than focusing solely on symptom suppression.