The therapeutic value of evening primrose oil (EPO) comes from its gamma linolenic acid (GLA) content, which has a number of diverse health benefits. GLA, an omega-6 essential fatty acid, has been shown to promote blood circulation, improve fatty acid balance, and support a healthy cycle of inflammation. EPO has also been shown to support joint mobility and comfort and promote healthy skin. Each capsule includes 1,300 mg of cold-pressed, organically grown evening primrose oil and 117 mg of GLA, in a convenient, high-dose soft gel capsule.
Evening primrose oil has a high concentration of GLA, which supports the production of prostaglandin E1 (PGE1). Prostaglandins are important cellular messengers with a variety of strong physiologic effects, especially on the cardiovascular and immune systems. PGE1 is known to enhance vasodilation and support healthy blood circulation, promote healthy inflammatory balance and strengthen immune function. By making blood platelets slippery, allowing for better blood flow, PGE1 helps to support arterial and cardiovascular health. PGE 1 also helps in modulating cholesterol synthesis and
maintaining normal blood pressure levels.
A large percentage of the population cannot efficiently convert dietary linoleic acid to GLA. There are a number of dietary factors and conditions which can inhibit the activity of the crucial enzyme that catalyzes the conversion of linoleic acid to GLA. These include a diet rich in saturated fats and processed vegetable oils, moderate to high alcohol consumption, aging, diabetic conditions , as well as deficient levels of zinc, vitamin C and vitamin B6.
EPO plays a key role in supporting normal levels of inflammation in various populations, including adults with blood sugar-related nerve complaints and women with hormonal imbalances.[1-3] The sterols in EPO have been found to promote healthy inflammatory balance by decreasing nitric oxide production, reducing tumor necrosis factor-?, interleukin 1? and thromboxane B?, as well as reducing eicosanoid release by inhibiting cyclooxygenase-2 expression.
Both in vitro and animal studies, including well-controlled, randomized clinical studies, suggest clinical benefit to EPO in supporting joint health.  Evidence from seven studies analyzed in a Cochrane review indicate that GLA from evening primrose oil reduces the intensity of joint discomfort and improves joint movement compared to placebo. A prospective 6-month, double-blind placebo controlled study of 19 patients receiving evening primrose oil (6 g/day), versus 21 subjects who received a placebo of olive oil, showed a significant reduction in morning stiffness at 3 months.
In a meta-analysis of placebo-controlled studies on skin health, both patient and doctor scores showed a highly significant improvement in skin dryness, scaling and itching in patients given EPO.
 A randomized, double-blind, placebo-controlled study of healthy adults testing the effect of EPO (1,500 mg twice a day for 12 weeks) on skin moisture, trans-epidermal water loss, redness, firmness, elasticity, fatigue resistance and roughness. In this study, it was found that at week 12, all measured variables, except skin redness, were significantly improved in the EPO group compared with placebo.  EPO has also been shown to have a stabilizing effect on the stratum corneum barrier of the skin when applied topically as a water-in-oil emulsion.