Evening Primrose Oil

Tori Hudson

(Oenothera biennis L.)


The evening primrose plant has been commonly known as tree primrose and sundrop. Evening primrose can be found in many parts of North America and are native in the northern temperate zone, especially at high altitudes. Only six or eight species of the 500 species of Primula are found in North America. They are mostly perennial herbs, flower in the spring and come in numerous colors but commonly, white and purple. The native people of North America as well as the English and pilgrims, were well aware of the healing properties of the leaves and bark as an astringent, nervine and sedative. It was often used for stomach and liver complaints, coughs and female disorders. Even the roots were eaten as a vegetable. The seeds were recommended as a coffee substitute in wartime and have a strong flavor similar to poppy seed oil. The therapeutic value of the seed oil is a more recent discovery. It is this seed oil, and its essential fatty acid content that holds the most interest today in maintaining health and preventi ng disease.

Understanding essential fatty acids

Quality oils and fats are actually essential in maintaining our health and in the prevention of certain chronic diseases. Our bodies need a healthy ratio of saturated, monounsaturated and polyunsaturated fats. Some polyunsaturated fats are as essential as vitamins and minerals for the maintenance of good health — these are the essential fatty acids (EFAs), or good fats.

We know we don’t get enough EFAs which play crucial roles in the body on a minute-by-minute basis. They produce hormone-like compounds; maintain cell membrane function; regulate pain, inflammation and swelling; dilate and constrict blood vessels; mediate immune response; regulate smooth muscle responses; prevent blood clots; regulate blood pressure and nerve transmission; regulate cholesterol levels; and even more.

Our bodies cannot make EFAs — they must be obtained from the diet or through supplementation. That is why they are called “essential fatty acids.” Under ideal conditions, the body uses linoleic acid (LA) to produce GLA (gamma linolenic acid-a polyunsaturated cis fatty acid). Likewise, the body uses alpha linolenic acid (ALA) to produce eicosapentenoic acid (EPA). In turn, GLA and EPA are used to produce beneficial hormone-like compounds called prostaglandins. Specifically, GLA is used to produce series one prostaglandins such as prostaglandin E1 (PGE1) while EPA is used to produce prostaglandin E3 (PGE3).

Prostaglandins affect the function of virtually every system in the body. These molecules are used in the regulation of inflammation, pain, blood pressure, fluid balance, blood clotting, and affect hormone production and function. In order to maintain a proper balance of the anti-spasmodic and anti-inflammatory prostaglandins (PGE1 and PGE3) with the pro-spasmodic and pro-inflammatory prostaglandins (PGE2), it is critical to have the proper amount of each fatty acid, particularly LA, GLA, ALA and EPA. The body has to receive a constant supply of EFAs and a balanced supply of each fatty acid in order to produce the right prostaglandins as they are needed. Without adequate amounts of GLA and EPA, prostaglandin production will be reduced, and problems will result.

Evening Primrose Oil is an omega-6 rich oil, containing both LA and GLA. It is by far the most popular and familiar source of GLA. Evening Primrose Oil contains 74% LA, 11% oleic acid, 6% palmitic acid, 2% stearic acid, and 9% GLA which is present in only a few other plant seeds.

The key to understanding the important need for supplementing with oils rich in GLA, such as evening primrose oil, is that many of us cannot convert LA to GLA efficiently. Dietary deficiencies, disease conditions, processed oils, trans-fatty acids, heated oils, alcohol, aging, viral infections and sugar consumption block, slow down, or interfere with the enzyme that catalyzes the conversion of LA to GLA.

Clinical Uses

Health problems supported and/or suggested by scientific trials using evening primrose oil include premenstrual syndrome, fibrocystic breast pain, eczema, sunburn, rheumatoid arthritis, diabetes, heart disease, osteoporosis and ulcerative colitis. Other conditions for which it may provide benefit include menopause and pregnancy.

Premenstrual syndrome

PMS has been linked to excessive and incorrect prostaglandin production. Specifically, women with PMS may have a deficiency of PGE1, at the central nervous system [1] and in other tissue such as breast tissue. Supplementing with EFAs may raise the body’s production of PGE1. The most popular and scientifically documented method is to supplement with GLA in the form of evening primrose oil in order to increase production of PGE1. Rigorous scientific studies have demonstrated that supplementing with EPO has a significant effect on symptoms of PMS. [2-4] The effects of EPO have been shown to improve all symptoms including premenstrual headaches, depression, irritability, and bloating. EPO also dramatically relieves premenstrual breast pain and tenderness. Oils that contain high quantities of GLA include evening primrose oil, borage oil and black currant oil.

Fibrocystic breast disease

The pain and tenderness of benign breast disease associated with cyclic breast pain and fibrocystic breasts has been alleviated with evening primrose oil in more than one scientific study. [5,6] In 1985, when 291 women took three grams per day of EPO for three to six months, almost half of the 92 women with cyclic breast pain experienced improvement, compared with one-fifth of the patients who received the placebo. In the course of treatment, it has been detected that women with breast pain have unusually low concentrations of GLA and metabolites from GLA. The concentration of GLA metabolites increases and the concentration of saturated fats in the breast decreases when patients are given supplements of evening primrose oil. This may also have long-term implications for prevention of breast diseases such as cancer.


Evening primrose oil and other oils containing GLA are popularly consumed by women to decrease the symptoms of menopause. GLA in the form of evening primrose oil was found to reduce the maximum number of nighttime flushing associated with menopause. However, there was no overall difference between the supplement and the placebo. [7] Many other herbal supplements are available to relieve menopausal symptoms and these may be used in conjunction with EFAs for greater benefit.


Although essential fatty acids have not been talked about much in relationship to osteoporosis, it appears evident from the research that has been done that we must expand our use of EFAs to maximize calcium metabolism and preserve bone health. There is a growing body of evidence and research to warrant advice about EFAs and calcium metabolism, bone health and the prevention of osteoporosis. EFAs have been shown to increase calcium absorption from the gut (in part by enhancing the effects of vitamin D), reduce urinary excretion of calcium, increase calcium that is deposited in the bone and improve the strength of bone. [8] Adults with osteoporosis who are given fish oil show an increase in calcium levels and an increase in urinary calcium clearance. [9] GLA in particular has been shown to reduce the excretion of calcium, [10] inhibit bone reabsorption and markers of bone turnover while at the same time increasing the levels of calcium content in the bone.

Pregnancy and fetal development

Essential fatty acids have a unique role during pregnancy because of the rapid development of new cell growth, new tissues, and new organ systems in a developing fetus. Fetal development is associated with a high EFA requirement, and this supply is dependent on the amount and availability of EFAs from the mother.

Prostaglandins are also involved in the development and clinical expression of pre-eclampsia (the simultaneous occurrence of the clinical triad of hypertension, edema, and protein in the urine at any time during the course of the pregnancy). These prostaglandins are modulators of vascular smooth muscle tone and platelet aggregation (blood platelets sticking together). Preeclampsia is characterized by increased vasoconstriction, frequently associated with increased platelet aggregation, reduced uteroplacental blood flow, and premature delivery. In a placebo-controlled clinical trial, a group of pregnant women receiving a combination of evening primrose oil and fish oil had a significantly lower incidence of edema. [12]


Nutritional supplementation of GLA is one of the most important tools in treating eczema as well as moisturizing the skin and protecting it from environmental oxidative damage. In eczema, supplementing the diet with evening primrose oil can provide gamma linolenic acid (GLA) that will correct the underlying metabolic defect. There have been many scientific studies using GLA with excellent benefits in improving the symptoms of eczema. [13-16] Dosages in the range of .5 to 3 grams of GLA are appropriate. Both evening primrose oils and borage oil have been used in these studies.

Sunburn and skin damage

Essential fatty acid supplementation should also be considered to provide the skin with the proper oils and moisture thereby preventing and reversing dry skin, preventing and reversing sun and age damage, and other environmental oxidative damage. The skin needs essential fatty acids, particularly when stressed by the damage that occurs with sunburn. Experiments have shown that UV rays cause a significant release of fatty acids from the cell membranes. The cell uses these fatty acids to regulate the inflammation, swelling and pain. GLA from borage, evening primrose and black currant oils have been found to reduce redness, swelling and pain from ultraviolet damage. In cases of an actual sunburn, you can take up to 8 capsules of evening primrose oil daily until the sunburn symptoms subside. Borage or evening primrose oil can also be applied topically to the burned area two or three times daily. When going on a sunny weather vacation, it would be smart to take 1-4 capsules of evening primrose oil daily when your sun exposure is increased.


Many studies on GLA have shown that individuals with RA experience significant improvements in their symptoms within the first six months of use. They also continue to improve by as much as 50% in the number of tender joints, 54% in the reduction of tender joints, 42% in the reduction in swollen joints, morning stiffness decreasing by 67%, and overall 27% reduction in pain., Studies on rheumatoid arthritis while using EPO also consistently show that individuals using 1500mg to 2800 mg of GLA daily can reduce the amount of their nonsteroidal anti-inflammatory medications.

Although there have been no human trials to date studying the effects of GLA on other forms of arthritis such as osteoarthritis, animal studies do show that GLA supplementation can have anti-inflammatory effects. Practitioners of natural medicine report that they see positive benefits using EPO supplements in osteoarthritis as well as rheumatoid arthritis.


Diabetes is associated with abnormalities in essential fatty acid metabolism. One of these abnormalities is the interference with the conversion of linoleic acid to gamma linolenic acid. By supplementing with GLA in the form of EPO, we can bypass this impairment and give the body what it was meant to have, an adequate amount of GLA. Individuals with diabetic-related neuropathies have been studied using GLA. Significant favorable changes have been observed in muscle strength, hot and cold thresholds, sensation, and reflexes. [19]

High cholesterol

Although fish oils and flax oil have received considerable attention in their role in reducing heart disease, due to their effects on blood lipids and blood pressure, we shouldn’t forget about the role of other essential fatty acids. For example, supplementing with 3 grams of GLA daily for 4 months has been shown to decrease triglycerides by 48%, increase HDL by 22%, and significantly reduce total and LDL cholesterol. [20] Not only should we include EPO supplementation in our heart disease treatment and prevention plans, but perhaps a well rounded EFA supplement approach.

High blood pressure

High blood pressure (a reading above 140/90) is another risk factor for heart disease. Over 60 double-blind studies have demonstrated that either fish oil supplements or flaxseed oil are effective in lowering blood pressure. Again though, we would be wise not to forget about the potential of EPO in this regard. In a study combining EPO plus fish oil, blood pressure was significantly lowered when compared to EPO plus sunflower and EPO plus flax oil. [21]

Ulcerative Colitis

EPO has been studied in individuals with ulcerative colitis. Although EPO did not reduce rectal bleeding or stool frequency, it did significantly improve the stool consistency. [22] EPO and other EFA supplements may prove to have a long term role in managing the symptoms of ulcerative colitis as well as the underlying chronic inflammatory condition. We look forward to more research in this area.

Other Effects

A study of psychiatric patients with tardive dyskinesia (abnormal involuntary movements) received EPO capsules over 4 months. Although EPO supplementation did not improve the abnormal movements, there was significant improvement in mental state, schizophrenic symptoms and memory. In a second phase, when zinc, niacin and vitamins C and B6 were added to EPO, there was marked and significant improvements in memory, schizophrenic symptoms and abnormal movement. [23-25]

In a clinical trial of alcoholics withdrawing from alcohol, EPO significantly reduced the severity of the withdrawal syndrome and improved liver function as well. In individuals who did not relapse, they reported improved memory and visual motor coordination while taking EPO supplementation. [26]

In a clinical trial of 89 kidney transplant patients who received either EPO or placebo along with their standard immunosuppressive medication, graft survival was significantly better in the EPO group compared to placebo within the first 3-4 months.


There has been some concern for the use of EPO in patients with a history of epilepsy. This concern arose from trials in patients with schizophrenia who were being treated with antischizophrenic drugs (phenothiazines). It was reported that episodes of epileptic seizures may have been aggravated or induced but no definite link to EPO treatment was determined. It may have been that side effects of the medication were more likely the cause. It is also extremely difficult to make a distinction between schizophrenia and temporal lobe epilepsy. In fact, the 3 individuals who had worsening of their seizures were later diagnosed with temporal lobe epilepsy.

To be cautious, it may be wise to avoid EPO in those with epileptic disorders due to the unlikelihood that EPO may have the potential to stimulate undiagnosed temporal lobe epilepsy. It would also be wise to avoid EPO when using phenothiazines.

There have been misleading reports about the safety of EPO and breast cancer patients, with some writers reporting that it is contraindicated. There is no reason to conclude this. EPO does not contain estrogen and is not stimulatory to the breast tissue. In fact, there are positive effects of EPO and breast tissue.

In the course of treatment of fibrocystic breast disease with EPO, it has been detected that women with breast pain have unusually low concentrations of gamma linolenic acid (GLA) metabolites. The concentrations of GLA metabolites increases and the concentration of saturated fats in the breast decreases when supplemented with EPO, a particularly concentrated source of GLA. Breast pain has also been associated with a high consumption of saturated fats and a very low fat diet can often relieve such pain. [28]

What is especially important to this discussion is that ovarian hormone levels are normal in women with breast pain and are not changed by therapy with GLA. Yet the abnormal sensitivity of the breast tissue to normal hormone levels does appear to be reduced by GLA supplementation. The proposed mechanism for the relief of breast pain with GLA is a shift in the balance of membrane fatty acids towards normal; the steroid receptors in the breast then have a reduced affinity for estrogen, and the excessive sensitivity of the breast to estrogen is lost.

No problems are associated with pregnancy or lactation and EPO and no toxic effects or carcinogenicity have been observed. Side effects that can occasionally occur in some individuals are headache and mild nausea.


(1.) Jakubowica D. The significance of prostaglandins in the premenstrual syndrome. In: Taylor R, ed. Premenstrual syndrome. London: Medical New-Tribune, 1983, p. 16.

(2.) Puolakka J, et al. Biochemical and clinical effects of treating the premenstrual syndrome with prostaglandin synthesis precursors. J Rep Med 1985;30(3):149-153.

(3.) Ocerman P, et al. Evening primrose oil as a treatment of the premenstrual syndrome. Rec Adv Clin Nutr 1986;2:404-405.

(4.) Casper R, A double blind trial of evening primrose oil in premenstrual syndrome. 2nd International Symposium on PMS, Kiawah Island, Sept. 1987.

(5.) Pye J, et al. Clinical experience of drug treatment for mastalgia. Lancet 1985;2:373-377.

(6.) Pashby N, et al. A clinical trial of evening primrose oil in mastalgia. Br J Surg 1981;68:801-824.

(7.) Chenoy R, Hussain S, Tayob Y, O’Brien PM, Moss MY, Morse PF. Effect of oral gamolenic acid from evening primrose oil on menopausal flushing. BMJ 1994 Feb 19; 308(6927):501-503.

(8.) Horrobin K. Calcium metabolism, osteoporosis and essential fatty acids: a review. Prog Lipid Res 1997;36(2-3):131-151

(9.) Papendorp D, Coetzer H, Kruger M. Biochemical profile of osteoporotic patients on essential fatty acid supplementation. Nutrition Research 1995;15(3):325-334.

(10.) Tulloch I, Smellie W, Buck A. Evening primrose oil reduces urinary calcium excretion oin both normal and hypercalciuric rats. Urol Res 1994;22:227-230.

(11.) Claasen N, Potgieter M, Seppa M, et al. Combination of evening primrose oil and fish oil influence bone resorption and bone calcium content. Bone 1995;16(Suppl): 385S-392S.

(12.) D’Almeida A, Carter J, Anatol A, Prost C. Women and Health, 1992;19(2/3):117-131.

(13.) Morse P. Horrobin D, Manku M. Meta-analysis of placebo-controlled studies of the efficacy of Epogam in the treatment of atopic eczema. Relationship between plasma essential fatty acid changes and clinical response. British J Derm 1989; 121:75-90.

(14.) Yasumoto R, Fujita H, Yamamoto T. The effectiveness, safety and usefulness of borage oil on atopic dermatitis. Acta Dermatologica 1996;92(2):249-251.

(15.) Pullman-Mooar S, Laposata M, Lem D, et al. Alteration of the cellular fatty acid profile and the production of eicosanoids in human monocytes by gamma-linolenic acid. Arthritis and Rheumatism 1990;33(10):1526-1533.

(16.) Andreassi M, Forleo P, DiLorio A, et al. Efficacy of gamma-linolenic acid in the treatment of patients with atopic dermatitis. J International Medical Research 1997; 25:266-274.

(17.) Zurier R, Rosetti R, Jacobson E, et al. Gamma linolenic acid treatment of Rheumatoid Arthritis. A randomized placebo-controlled trial. Arthritis Rheumatology, 1996; 39(11):1808-1817.

(18.) Leventhal L, Boyce E, Zurier R. Treatment of Rheumatoid Arthritis with gamma-linolenic acid. Annals of Internal Medicine 1993;119:867.873.

(19.) Keen H, et al. Treatment of diabetic neuropathy with gamma linolenic acid. Diabetes Care 1993;16:8-13.

(20.) Guivernau M, Meza N, Barja P, et al. Prostagland Leukot Essent Fatty Acids 1994;51(5):311-316.

(21.) Venter C, Joubert P, Booyens J. Prostagland Leukot Essent Fatty Acids 1988;33(1):49-51.

(22.) Greenfield S, Green A, Teare J, et al. Aliment Pharmacol Ther 1993;7(2):159-166.

(23.) Vaddadi K. Prostagland Leukot Essent Fatty Acids 1992;46(1):67-70.

(24.) Vaddadi K, Courtney P, Gilleard C, et al. Psychiatry Res 1989;27(3):313-323.

(25.) Vaddadi K. Prostaglandins Leukot Essent Fatty Acids 1996;55(102):89-94.

(26.) Hoorobin D. Rev Contemp Pharmacother 1990;1:1-45.

(27.) McHugh M, Wilkinson R, Elliott R, et al. Transplantation 1977;24(4):263-267.

(28.) Boyd N, et al. Effect of low-fat, high-carbohydrate diet on symptoms of clinical mastopathy. Lancet 1988; ii: 128-132.

COPYRIGHT 2001 The Townsend Letter Group

COPYRIGHT 2008 Gale, Cengage Learning

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