Is evening primrose oil a substance that can produce almost miraculous improvement, as numerous anecdotal reports allege, or is it just another form of snake oil?
Until recently, little data confirming or refuting its possible efficacy existed. Dr. Peter Behan, at Glasgow University (Scotland), has performed two controlled clinical trials comparing the effects of evening primrose oil with an inert placebo and has found a marked clinical improvement in people with Chronic Fatigue Syndrome (CFS), who took controlled doses of evening primrose oil. No adverse effects of the treatment were reported.
Evening primrose oil is an essential fatty acid (EFA), an essential nutrient that is required for healthy cell functioning. Like vitamins, EFAs must be provided in the diet because the body is unable to manufacture them.
The crucial step in metabolizing EFAs so that they can be used by cells is called “6-desaturation,” and that step is known to be inhibited by the hormones released during stress (adrenaline and hydrocortisone), by aging, diabetes, and high alcohol intake. This metabolic step has also been shown to be reduced in people who have certain forms of eczema, hypertension, high cholesterol levels, and viral infections.
The substance extracted from evening primrose oil and used as a pharmaceutical is gamma-linoleic acid (GLA), which is often administered in conjunction with another EFA derived from fish oil.
Interestingly, GLA is present in substantial amounts in human milk, but not in cow milk or baby formulas. In Japan, evening primrose oil is considered so safe that it is added to infant formula to make it more like human milk.
Although evening primrose oil is sold as a nutritional supplement in more than 30 countries, the U.S. Food and Drug Administration regards it as a potentially unsafe substance and is currently attempting to ban the sale of it.
Behan and colleagues performed a controlled clinical trial of the efficacy of Efamol Marine (which contains 35 mg. of GLA and 17 mg. of concentrated fish oil extract, another type of essential fatty acid) as compared to an inert placebo in patients with CFS (called “postviral fatigue syndrome” in their study) which was published in a Scandinavian medical journal. “We considered the possibility that disordered metabolism of fatty acids might play a role in the syndrome,” Behan and co-workers explain. They further note “Serum fatty acid levels are known to fall in several acute and chronic viral infections, and may remain persistently low, correlating with the physical malaise after, for example, acute Epstein-Barr virus infection.”
These acids also play important roles in immunity since arachidonic acid is the immediate precursor of eicosaonoids, the family of biologically active substances which includes the prostaglandins (essential to many physiological processes, such as vasodilatation, and contraction of smooth muscle groups) and leukotrienes (involved in allergic reactions). Finally, both saturated and unsaturated fatty acids may inactivate certain viruses in vitro and inhibit their replication in vivo.
Sixty-three patients took part in the study: 27 men (aged 21-63) and 36 women (aged 22-56). All had experienced severe symptoms for one to three years, including “overwhelming fatigue” made worse by exercise, muscle pain, depression, and “poor concentration and short-term memory” following a viral infection characterized by respiratory or gastrointestinal symptoms.
“In addition to the above symptoms, all the patients also complained at some time of palpitations, shooting pains in the chest and unsteadiness,” according to Behan and colleagues. All had been in good physical and mental health before the precipitating viral infection. Other causes of these symptoms had been in ruled out in the patient group.
The patients were randomly as-signed to either placebo (24 patients) or treatment (39 patients) group; clinicians assessing the patients did not know to which group the patient was assigned. At each visit, the physician assessed fatigue, muscle pain, dizziness, poor concentration, and depression. The patient was asked to assess his or her “overall condition,” as to whether he or she felt worse, unchanged, or better than when the study began.
Blood samples were also drawn from several members of each group of patients (19 receiving treatment and 13 receiving placebo) at the beginning and end of the trial to measure the concentration of fatty acids in red blood cell membranes.
Patients were assessed at one and three months after the beginning of the trial. At the one-month mark, improvement in all symptoms was found in both treatment and control groups, “but the degree of improvement was greater in the actively treated patients, reaching statistical significance for myalgia.”
At three months, however, the improvement in the treatment group from their baseline assessments “was significantly greater for all symptoms than in the patients given placebo. . . in contrast, in the placebo group each symptom had worsened compared with the score at one month, almost completely reversing the previous benefit.”
This placebo effect is obvious when the number of patients in each group citing improvement are examined: At one month, 74% of patients in the treatment group were considered improved, compared with 23% in the placebo group. At three months, the difference was “even more striking”: 85 percent of the treatment group was improved, while only 17% of the placebo group was improved.
The evaluation of red cell membrane fatty acids revealed that patients with CFS “had significantly reduced levels of total EFAs.” Although all of the patients in the trial showed a tendency for this parameter to approach normal values, in the treatment group, “the shifts toward normal were substantially greater and most of them were statistically significant.”
These authors conclude: “The results reported here indicate that a three-month trial of essential fatty acids in patients with PFS (postviral fatigue syndrome) led to a significant improvement in symptoms, especially fatigue, myalgia, and depression, with general feeling of benefit in 85% of those treated, as against 17% of those taking placebo.” They note that, while none of the patients were “cured,” their improvement was “gratifying.” Many were able to return to work, and their relatives “commented on the beneficial change.”
“We do not know how the EFAs produced their effect,” Behan and colleagues admit, but they reiterate that these substances are decreased in patients with severe Epstein-Barr virus , and that a return to the natural fatty acid pattern accompanied clinical improvement, while persistence of the biochemical abnormalities was associated with continuing symptoms.”
“In conclusion, our study shows that a treatment for PFS (postviral fatigue syndrome) based on a biochemical abnormality known to be produced by certain viral infections can lead to significant clinical improvement,” Behan and colleagues state.
Although Behan and colleagues’ results need to be confirmed by other researchers, these preliminary findings appear to demonstrate that evening primrose oil, may, in fact, have some efficacy in treating an underlying immune dysfunction in CFS.
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Horrobin, D.F. “Essential Omega-6 and Omega-3 Fatty Acids in Medicine: A Practical Guide,” Journal of Advancement in Medicine 3(3), Fall 1990.
Behan, P.O., W.M.H., and Horrobin, D. “Effect of High Doses of Essential Fatty Acids on the Postviral Fatigue Syndrome,” Acta Neurol. 82:209, 1990.
Behan, Peter O., and Wilhelmina M.H. Behan “Essential Fatty Acids in the Treatment of Postviral Fatigue Syndrome,” an unpublished manuscript.
Reprinted with permission from the New York Native and Neenyah Ostrom.