The oil that comes from the seeds of the evening primrose plant contains a high amount of its active ingredient, gamma-linolenic acid (GLA), an oil much like the essential fatty acids (EFA) of the omega-6 variety. In fact, GLA is a precursor of the EFA arachidonic acid, but even more important to its potential therapeutic benefits, GLA leads to the important prostaglandin E1 series (PGE1).
The use of evening primrose oil as a nontoxic source of GLA is a good mix of nutrition and herbal medicine. Actually, this night-blooming, bright yellow flowering plant is not a true primrose but is part of the willow family. The name comes from the fact that its flowers resemble those of the primrose plant. This herb has been used medicinally for centuries—externally, as a poultice for skin problems and internally to treat variety of complaints, such as asthma, gastrointestinal problems, gynecological problems, or to enhance wound healing. Native Americans used this plant and its seeds commonly, and in England it was known as "King’s cure-all."
There has been a great deal of research with GLA in the last decade, much of it conducted in England where the majority of evening primrose oil is made. With close to 100 research papers published and many more in progress, the results are mixed. Most of the findings, though, are positive and promising, particularly in regard to clearing or reducing symptoms in arthritis, skin problems, and premenstrual syndrome, as well as for all kinds of inflammatory problems, cardiovascular disease, and immunodepression.
Our bodies can make some gamma-linolenic acid from one of the essential fatty acids, linoleic acid, and from this GLA, we form prostaglandin E1 series. Many symptoms occur from deficiency of linoleic acid, and many of these may be contributed to by low PGE1 levels, which also may arise from reduced or blocked steps in fatty acid metabolism. Many of these aspects are still unknown. When we take additional GLA, we encourage increased formation of PGE1, which produces a variety of effects.
The prostaglandin E1 series is probably the most important of the hormonelike prostaglandins. These substances help inhibit or reduce inflammation, platelet aggregation, thrombosis, cholesterol synthesis, blood vessel tone, and the formation of abnormal cells. PGE1 is also thought to help lower blood pressure and protect the liver from the effects of alcohol and other irritating drugs. This prostaglandin also functions in maintaining the salt and water balance, insulin secretion, nerve conduction, and gastrointestinal function.
Other prostaglandins, such as series 2, have different functions; some, in fact, can stimulate inflammation. Series 3 prostaglandins are generated in part by the fish oils (discussed next) and have some anti-inflammatory status, but the GLA oils, which enhance PGE1 formation and provide a good anti-inflammatory effect, have been more thoroughly evaluated in regard to their role in protecting us from cardiovascular disease. Gamma-linolenic acid may help reduce arterial spasm and clotting, two important factors besides vascular inflammation that may contribute to blood vessel disease and cardiac problems. GLA also seems to help the immune system. The following list outlines problems for which evening primrose oil (GLA) has been used with some success and the theoretical bases for its beneficial action.
- Cardiovascular disease—anti-inflammatory effect; reducing platelet aggregation, thereby reducing clotting; lowering blood pressure by decreasing vessel tone; cholesterol-lowering effect.