Evening Primrose Oil (EPO) — Gamma-linolenic acid (GLA)

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.

  • Arthritis (rheumatoid arthritis and other inflammatory disorders)—anti-inflammatory effect; immune support; correcting possible EFA and GLA deficiency.

  • Skin disorders (eczema, acne, dermatitis)—anti-inflammatory effect; EFA functions; immune support.

  • Allergies, asthma—anti-inflammatory effect; EFA function; immune support.

  • Weight loss (theoretical)—increased cellular metabolism; electrolyte and water balance.

  • Premenstrual syndrome (theoretical)—electrolyte and water balance; EFA support (correction of possible deficiency).

  • Multiple sclerosis—nerve conduction; correction of possible EFA and GLA deficiency; immune support; decreased platelet aggregation; balancing prostaglandins.

  • Benign (fibrocystic) breast disease (theoretical)—correction of possible deficiency of PGE1; possible anti- inflammatory effect.

  • Hyperactivity in children—unknown effect; GLA and EFA support; reduced allergies.

  • Schizophrenia—correction of low omega-6 fatty acids, low PGE1, and high PGE2.

  • Alcohol protection—reduced withdrawal symptoms, liver toxicity, and nervous system depression.

  • Depression—correction of possible GLA deficiency.

The use of evening primrose oil is still experimental, but the research is very promising. It is not necessarily curative by any means, especially in diseases such as atherosclerosis, arthritis, and multiple sclerosis, but it may be helpful in reducing symptoms and/or in preventing further complications. I have recently become more enthusiastic about the use of gamma-linolenic acid because of the results my patients have been experiencing. Many people with arthritis pain, premenstrual syndrome and breast symptoms, skin disorders, and some allergies have had a good response, especially when GLA is used in combination with vitamin E and beta-carotene.

Side effects from the use of evening primrose oil are almost nonexistent. Some nausea may be experienced initially because of the oils, but this can be avoided if it is taken with food. Mild skin rashes or acne can occur occasionally; otherwise, no problems have been noticed.

The recommended amount of evening primrose oil is between 500–1,000 mg., taken two or three times daily, with possibly higher doses (4–6 grams daily) in problems such as arthritis, asthma, or eczema. Most good primrose oils contain about 35–40 mg. of GLA per 500 mg. capsule; thus, we are using a therapeutic amount of 150–250 mg. GLA daily. Usually, I suggest a good-quality vitamin E, particularly for the premenstrual and breast problems, and specifically the active d-alpha tocopheral in one or two dosages of 400 IUs each to act with the GLA.

We should follow this interesting nutrient closely in the upcoming years. Other recently available sources of gamma-linoleic acid include black currant seed and borage seed oils, which can be even more concentrated in GLA than primrose, producing similar effects with less capsules and expense. Though these sources have not been evaluated as extensively as EPO, they may be good substitutes.

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Written by Elson M. Haas MD

Explore Wellness in 2021