Evening primrose (Oenothera biennis) seed oil contains gamma-linolenic acid (GLA). Oral evening primrose oil (EPO) has been used to treat Raynaud’s phenomenon of the nipple in nursing mothers. It is also used for premenstrual syndrome, cyclical mastalgia, and atopic dermatitis. Supplementation of nursing mothers with EPO increases the breastmilk content of linoleic acid and total GLA plus its metabolite, Duomo-gamma-linolenic acid, and caused no adverse reactions in the breastfed infants. Supplementation of mothers with GLA had no effect on the development of atopic dermatitis in their breastfed infants. Evening primrose oil is "generally recognized as safe" (GRAS) as a food by the U.S. Food and Drug Administration.
Heating breastmilk to 63.5 degrees C reduces the concentration of linolenic acid by about 22%. Freezing milk at -20 degrees C and thawing more than once decreases linolenic acid concentration by an average of 63%. Dietary supplements do not require extensive pre-marketing approval from the U.S. Food and Drug Administration. Manufacturers are responsible to ensure the safety, but do not need to prove the safety and effectiveness of dietary supplements before they are marketed. Dietary supplements may contain multiple ingredients, and differences are often found between labeled and actual ingredients or their amounts. A manufacturer may contract with an independent organization to verify the quality of a product or its ingredients, but that does not certify the safety or effectiveness of a product. Because of the above issues, clinical testing results on one product may not be applicable to other products. More detailed information about dietary supplements is available elsewhere on the LactMed Web site.