Evening primrose (Oenothera biennis)
The seed of this yellow wildflower may help ease PMS, diabetic neuropathy, and rheumatoid arthritis

By Laurel Vukovic

What it is
A native North American wildflower, evening primrose is commonly called ?evening star? because its bright yellow flowers open at dusk. It?s a favorite with herb and native plant gardeners and can grow up to 4 feet or 5 feet tall. The seeds are a rich source of gamma-linolenic acid (GLA), an essential fatty acid with wide-ranging health benefits.

History and folk remedies
Native Americans valued evening primrose both as a food and a medicine. They applied a poultice made from the plant to bruises to relieve swelling and made a tea from the root to ease coughs. European settlers took their cue from native peoples, using evening primrose to treat wounds, coughs, sore throats, and digestive upsets. In the 1980s, evening primrose soared in popularity when researchers discovered that its seeds are a gold mine of GLA, a compound rarely found in plants.

Why it?s used
Evening primrose oil (EPO) is used to treat a variety of health problems caused by a deficiency in essential fatty acids. These include premenstrual syndrome (PMS), fibrocystic breast pain, eczema, rheumatoid arthritis, and diabetic neuropathy. Other conditions that evening primrose may help treat include high blood pressure, high cholesterol, attention deficit disorder, and ulcerative colitis.

How it works
GLA is essential for the production of prostaglandins, hormonelike compounds that influence almost every bodily system. Prostaglandins decrease inflammation, stimulate hormone production, and help regulate blood clotting, blood pressure, and PMS-related water retention.

It takes as many as 5,000 evening primrose seeds to produce one capsule of oil. If the body is working properly, it converts omega-6 fatty acids (found in vegetable oils, nuts, and seeds) into GLA. But many factors can inhibit this conversion, including advancing age; a diet compromised by excessive saturated fats, trans fats, or alcohol; zinc deficiency; and some medical disorders, such as diabetes, multiple sclerosis, and cancer. Evening primrose oil supplies a direct source of GLA to the body, bypassing the need for conversion of omega-6s and helping to restore healthy levels of prostaglandins.

Scientific support
One of the most common uses for evening primrose oil is treating PMS, though study findings have been conflicting. The uneven results may indicate that EPO supplementation helps only those women deficient in essential fatty acids.

In colonial America, evening primrose seeds were often substituted for poppy seeds in baking. More compelling is research supporting the use of evening primrose oil for diabetic neuropathy, a common complication of long-term diabetes that causes nerve damage in the legs, feet, arms, and hands. One double-blind study evaluated 111 people with diabetes for one year who were given either 480 mg of GLA daily or a placebo. The researchers found that those given GLA experienced significant improvement in neurological symptoms (Diabetes Care, 1993, vol. 16, no. 9).

GLA also has shown promise as an effective treatment for rheumatoid arthritis, a painful and disfiguring type of inflammatory arthritis. In a 1996 study, researchers gave 56 patients with active rheumatoid arthritis GLA supplements or a placebo. After six months of treatment, participants taking GLA experienced reduced arthritic symptoms (Arthritis and Rheumatism, 1996, vol. 39, no. 11). Further research is needed to confirm all of these findings.

Forms
Evening primrose oil is sold in gelcaps. To prevent rancidity, EPO should be refrigerated and used by the expiration date.

Dose
The amount of GLA per capsule varies and is stated on the container; a general recommendation is 240 mg of GLA daily (for diabetic neuropathy, the dose may be 480 mg daily). As always, check with your health care provider for proper dosage.

Cost
A month?s supply of evening primrose (240 mg daily) costs approximately $10 to $15. Substituting borage or black currant oil, also excellent sources of GLA, may be an effective and less expensive option. Check with your health care provider for specific recommendations.

Side effects
EPO is generally considered safe. Side effects are rare; a small percentage of people in clinical studies reported nausea, upset stomach, or headache.

Herbalist Laurel Vukovic lives in Ashland, Oregon, and has published nine books, including Herbal Healing Secrets for Women.