Evening Primrose Oil Benefits and Side Effects

Posted By elissa on Jan 1, 2010 | 1 comment

Evening primrose is a wildflower that grows throughout North America, Europe and some parts of Asia. The seeds of this plant (Oenothera biennis) contain oil that is rich in gamma-linolenic acid (GLA), which is an omega-6 essential fatty acid (EFA). The body converts GLA into prostaglandins, substances that function like hormones and help to regulate body processes.

Evening primrose oil (EPO) is often recommended as an alternative treatment for premenstrual syndrome, menopausal symptoms, breast pain (mastalgia) and inflammatory diseases such as eczema/atopic dermatitis, rheumatoid arthritis and diabetic neuropathy.

Theoretically, it should be useful: dietary GLA is converted to a compound known as dihomo-gamma-linolenic acid (DGLA), which is used by the body to produce prostaglandins with anti-inflammatory effects. It may also attenuate the production of inflammatory prostaglandins from arachidonic acid, another essential fatty acid metabolite.

In reality, however, human clinical trials have had mixed results. This may be due to the range of doses used in various studies. For example, a recent review concluded that GLA supplementation from either borage, black currant or EPO “showed benefit in the alleviation of rheumatic complaints“—but only in doses equal to/greater than 1400mg GLA per day. Lower doses (i.e., 500mg/day) were not effective.

This makes it difficult to come to firm conclusions on whether EPO is useful for treating specific conditions or not.

To take another example, one recent study demonstrated that EPO may help diminish some (but not all) of the symptoms of atopic dermatitis—a type of eczema that results in itchy, red, inflamed skin.

Nonetheless, negative studies on EPO (or other sources of GLA) also exist.

So is EPO useful for atopic dermatitis or not?

Conventional medicine suggests “not”—but individuals may wish to experiment. Fortunately, GLA supplementation appears to be a relatively safe intervention, even for young children.

There is also some preliminary evidence from animal experiments that suggest EPO may improve diabetic neuropathy as well as microvascular complications. In addition, EPO supplementation may help inhibit bone resorption and prevent osteoporosis, but far more research needs to be done before it can be recommended for the human versions of these conditions.

The same thing can be said for the use of Evening primrose oil as a treatment for cancer or cardiovascular disease. In-vitro studies suggest that GLA has cytotoxic effects against certain types of cancer cells; and that it may amplify the activity of anti-cancer drugs—but this research is still preliminary. Likewise, animal experiments suggest EPO has anticoagulant effects and can retard the development of atherosclerotic lesions, but reliable human studies are lacking.

EPO is often seen as a women’s supplement, due to its reputation for relieving menstrual/menopausal complaints. Unfortunately, there’s little hard evidence that EPO is useful for treating cyclic mastalgia, premenstrual syndrome (PMS) or menopausal hot flashes (one study concluded that beneficial effects on PMS were due to the “placebo effect”). EPO has not been found to be beneficial for asthma, attention deficit disorder or weight loss either (although GLA supplementation may help reduce weight regain).

Evening primrose oil is available in capsules and in liquid form. Side effects are uncommon but may include bloating and abdominal discomfort in a small percentage of people.To minimize any unpleasant side effects from the use of evening primrose oil capsules, it is best to take them with food. EPO supplementation is not recommended for pregnant women or people with seizure disorders.