From the Manufacturer:
Evening Primrose Oil is derived from plant sources and contains high amounts of Essential Fatty Acids, which the body cannot produce alone. These acids are converted by the body into GLA (Gamma Linolenic Acid), which is a building block for prostaglandins. Prostaglandins are hormones which help regulate the immune system and can only be produced when adequate Essential Fatty Acids are present. Prostaglandins serve as regulators of metabolism, cell growth and reproduction.
GLA is a critical nutrient necessary to prevent hardening of the arteries, heart disease, PMS, multiple sclerosis and high blood pressure. GLA aids in lowering cholesterol levels, helps regulate the production of the sex hormones, estrogen and testosterone, and is important in combating cirrhosis of the liver. Women suffering from breast cancer that is estrogen related should avoid or limit their intake of EPO.