Herbs & Supplements

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Uses

Oil pressed from the seeds of evening primrose plants contains large amounts of polyunsaturated omega-6 fatty acids (PUFAs). These are among the essential fatty acids (EFAs) needed by the human body to regulate activities such as heart function, insulin utilization, and mood balance. The body cannot produce EFAs, so they must be eaten in the diet or taken as supplements. Estimates are that between 65% and 80% of evening primrose oil is composed of the EFA linoleic acid and between 2% and 15% is another EFA, gamma-linolenic acid (GLA). Linoleic acid may play a role in utilizing insulin, maintaining weight, and resisting cancer and heart disease.

After being digested, linoleic acid is converted into GLA, which is believed to interrupt the body's production of chemicals that initiate and prolong inflammation. Therefore, evening primrose oil is often used to treat inflammatory conditions such as rheumatoid arthritis (RA) and asthma. In multiple animal and human studies, taking evening primrose oil reduced inflammation, joint damage, and pain from RA. However, relief took up to 6 months to reach full effectiveness for some individual study participants. Results from other studies were inconclusive, with many finding little or no effectiveness for evening primrose oil in asthma and other inflammatory conditions. Some very early findings from additional studies suggest that evening primrose oil may be useful in treating chronic fatigue syndrome, but more research is needed before evening primrose oil can be recommended for any condition.

In animal studies, oral doses of evening primrose oil have shown some promise for the treatment of heart diseases, high blood pressure, and high cholesterol. General decreases in blood pressure were seen in animal studies of linoleic acid use and in both animal and human studies of GLA supplementation. Evening primrose oil has been shown to reduce the clumping of blood components called platelets. As a result, atherosclerosis (hardening of the arteries) may be delayed or prevented. Results for the cholesterol studies are not as clear--in some studies, only triglycerides were reduced while other studies showed overall reductions in cholesterol. It is believed that several processes, including the possible relaxation of blood vessel walls, are involved in the potential use of evening primrose oil for these conditions. More studies are needed, though, before evening primrose oil can be recommended for preventing heart diseases or high cholesterol.

Possible relaxing of blood vessels by evening primrose oil has also been studied for treating Raynaud's syndrome. Resulting from tightening of tiny arteries in the ears, fingers, nose, and toes; Reynaud's syndrome is caused by stress or exposure to cold. It may also be associated with autoimmune diseases, such as scleroderma. Also known as systemic sclerosis, scleroderma is a disorder of connective tissues that causes the skin to become thick and hard. It may also attack internal organs and joints. In a few small studies, individuals taking evening primrose oil generally had fewer symptoms of Raynaud's syndrome than individuals who took a placebo (inactive capsules).

Chemicals called isoflavones, which belong to a larger class of plant chemicals known as phyto (plant-derived) estrogens, are contained in evening primrose oil. Because isoflavones are similar in shape to the female hormone, estrogen, they may attach to estrogen receptors. Potentially, they may displace some of the natural estrogens in the body --possibly preventing or relieving estrogen-related symptoms, such as breast pain, that are associated with premenstrual syndrome (PMS). Additionally, women who have PMS may also have a decreased ability to convert linoleic acid into GLA. Some evidence shows that symptoms of PMS and menopause may be worsened by deficiencies of EFAs. Therefore, both its isoflavones and its EFAs may give evening primrose oil some ability to reduce symptoms of PMS and menopause.

Because it may cause contractions of the uterus, evening primrose oil has been used by midwives to start labor for pregnant women. However, no reliable studies support this use of evening primrose oil, prescription medications are more effective, and labor should only be initiated by a healthcare professional who is familiar with the procedure.

Both oral and topical forms of evening primrose oil have also been studied for treating acne, eczema, psoriasis, and other skin conditions. In several studies dating as far back as the 1980s, itching, redness, and swelling of eczema has been reduced after 2 weeks to 4 weeks of treatment with evening primrose oil. In a study of individuals with dry eyes due to wearing soft contact lenses, taking evening primrose oil capsules for 6 months reduced symptoms and improved comfort. Although its effectiveness has not been proven, evening primrose oil continues to be studied for these uses. When it is applied to the skin, evening primrose oil has moisturizing and softening effects, so it is often included in cosmetics such as face cream.