Other Common Names: King’s cure-all, night-willow herb, scabish, German rampion, Flor de San Juan. 1
Evening Primrose is an annual or biennial shrub, which grows to a height of up to 3 m and produces evening-blooming fragrant yellow flowers. The fruit, a dry pod up to 4 cm long, bears numerous small seeds, the source of evening primrose oil (EPO). 2
Evening primrose is native to North and Central America, but is now cultivated throughout most of Europe and parts of Asia.
Evening primrose’s medicinal quality derives from its seed oil. The oil consists of linoleic acid (65-80%), gamma-linolenic acid (GLA) (8-14%), oleic acid (6-11%), palmitic acid (7-10%), stearic acid (1-2%) and alpha-linolenic acid (ALA) (0.1-0.2%). 3
While the GLA content of EPO ranges between 7 and 10%, borage (Borago officinalis L.) seed oil is reported to contain 17-25% and black currant (Ribes nigrum) seed oil 15-19%. 4
EFA is metabolized in alternating steps of desaturation and elongation to dihomo- gamma-linolenic acid (DGLA) and arachidonic acid. GLA in EPO, is converted to DGLA in the body. These are precursors to chemical regulators which participate in many biological functions including the inflammatory and immune processes.
Altering essential fatty acid content of the diet or administering different EFA as supplements can adjust production of different prostaglandins and leukotrienes.
Diets rich in arachidonic acids form the 2-series prostaglandins and 4-series leukotrienes, which have pro-inflammatory effects. Ingestion of EPO elevates the concentrations of DGLA, which acts as a competitive inhibitor of 2-series prostaglandins and 4-series leukotrienes, suppressing inflammation.
No health hazards are known in concurrence with the proper administration of designated therapeutic doses.
Over 4000 people have taken GLA or EPO in scientific studies with no noted adverse effects.
The maximum safe doses of GLA for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been established. Consultation of a physician is therefore recommended for such patients.
Platelet Aggregation: EPO increases the production of series-1 prostaglandins, which display anti-thrombotic activity.
De La Cruz and colleagues showed that EPO reduced platelet hyperaggregability in rabbits fed an atherogenic diet for 6 weeks. The control group was fed a normal diet, 3 other groups were fed either an atherogenic diet, a normal diet with 15% EPO, or an atherogenic diet with 15% EPO. The findings showed that the platelet hyperaggregation caused by a diet rich in saturated fat was reduced when 15% EPO was added. Thromboxane synthesis and lipid peroxide concentrations were also lowered by feeding EPO. 7
Atopic Eczema (Dermatitis)
Biagi and colleagues gave 51 infants
either high dose EPO (0.5 g/kg/day), low dose
EPO (50% mix, 0.5 g/kg/day) or placebo
capsules for 8 weeks. A significant
improvement was seen in the high dose group
vs. placebo for overall physician-rated severity
in eczema. The authors concluded that the
overall severity of atopic eczema improved
significantly on a high dose of EPO. 8
Hederas and colleagues gave participantsEpogram (500 mg EPO, 40 mg GLA, 10 mg vitamin E) or placebo for 16 weeks. After 4 weeks, eczema symptoms of patients treated with EPO significantly improved vs. placebo. The authors concluded EPO substantially improved clinical symptoms of atopic eczema in 2/3 of the treated children after 4 weeks of therapy. 9
Wright and Burton in a 1982 double-blind controlled cross-over study of the effect of oral doses of EPO in 99 patients (60 adults and 39 children) with atopic eczema reported positive effects; fairly high doses of EPO (6g/d in adults, 2g/d in children) were administered over a 12-week period. No side effects were noted . 10
Bamford et al. conducted a randomized, double-blind crossover trial in 123 patients with the same capsules used by Wright and Burton and found no differences between the placebo and therapy groups, nor was there a dose-response effect. 11 Bamford et al. pointed out that Wright and Burton’s patients had a worse clinical picture, that there were differences in initial arachidonic acid concentrations and that a different placebo (without vitamin E) was used. The Bamford et al. placebo, at highest dose, administered 160 IE of vit. E – about 16 times the officially recommended daily dose!
A meta-analysis of 9 trials (5 crossover) including Wright and Burton, but excluding Bamford et al., reported positive results 12 but, more recently, a parallel trial of 123 patients yielded negative results. 13 Clearly more research is needed to firmly assess EPO for this indication.
Rheumatologic Conditions
Manipulation of essential fatty acids through diet or supplementation may be effective for treating inflammatory disorders.
A review by Belch and Hill stated that the results, so far, are inconclusive for EFA in treatment of Raynaud’s phenomenon and Sjögren’s syndrome. 14 Sjögren’s syndrome is characterized by a decrease of lachrymal and saliva production and a lympho/plasmacellular infiltrate in the glands; about half of patients suffering from the disease also suffers from rheumatoid arthritis. 15
Zurier et al evaluated a high dose of EPO equivalent to 2.8 g GLA/day. The verum treatment showed a significant improvement in symptoms of rheumatoid arthritis compared to placebo. . The treatment was well tolerated. 16
An earlier randomized double-blind placebo-controlled 24 –week study with 37 patients with rheumatoid arthritis and active synovitis administered borage oil capsules equivalent to 1.4g GLA daily. Clinically important reduction in the signs and symptoms of disease activity were noted for four outcome measures, namely number of tender joints, tender joint score, swollen joint count and swollen joint score, whereas the placebo group did not show significant improvement in any measure. 17
Premenstrual Syndrome (PMS)
There are conflicting findings on use of EPO as a treatment for premenstrual symptoms.
Four trials (3 crossover) have reported positive
results, 18 but more recently, Khoo et al. found
no differences between EPO and placebo in a
crossover trial in 38 women. 19
Mastalgia
In assessing the effects of EPO on mastalgia
(pain and tension in the breasts) none of the
symptoms of PMS were judged to be
significantly improved in three small
randomized trials. 20
Pye et al. treated 291 mastalgia patients with
one or more of four drugs, including EPO and
bromocriptine in an uncontrolled study. 21 Of
those receiving EPO (3g/d) for 3 to 6 months,
45% obtained an ‘excellent’ response, as
compared to 47% for bromocriptine. Side-
effects with EPO were minimal, but 21% of
responders relapsed after one course of
treatment.
N.B. General agreement has not so far been attained in the scientific community regarding the efficacy of EPO or other GLA-rich seed oils for treatment of any disease condition. Notably Kleijnen et al,. 5, 15 who find EPO promising in the treatment of atopic dermatitis and indicate other applications warranting further research, judge that clinical trials so far conducted have not been sufficiently rigorous to establish efficacy. These Dutch epidemiologists particularly note a high incidence of methodological defects in the trials, chiefly involving limited numbers of subjects, inadequate description of randomization procedures, lack of proper blinding routines and insufficient attention to compliance.
Dietary GLA is seen as essential in a preventative or ameliorative role in a variety of ailments where tissue concentrations of GLA and other fatty acids are abnormally low in tissues central to the etiologies of these pathologies.
EPO has been used to treat a variety of disorders, including atopic eczema (dermatitits), rheumatoid arthritis, neurodermatitis, diabetic neuropathy, multliple sclerosis, various cancers, Raynaud’s phenomenon, ulcerative colitis, pre-eclampsia, premenstrual syndrome, menopausal flushing, breast cysts, mastalgia, Sjögren’s syndrome, schizophrenia, and hyperactivity. 5 It is approved in Germany to treat symptoms of atopic eczema, and in the U.K. for mastalgia as well. In Canada it is approved as treatment for conditions associated with deficiency of essential fatty acids (EFA).
There is an increased risk of temporal lobe epilepsy when this herb is combined with drugs that decrease seizure threshold, such as the phenothaiazines, chlorpromazine [Thorazine] and trifluoperazine [Stelazine], used in the treatment of schizophrenia. 6 Information on the relationship between substances and disease is provided for general information, in order to convey a balanced review of the scientific literature. In many cases the relationship between a substance and a disease is tentative and additional research is needed to confirm such a relationship.
The dietary supplement information contained on this site has been compiled from published sources thought to be reliable, but it cannot be guaranteed. Efforts have been made to assure this information is accurate and current. However, some of this information may be purported or outdated due to ongoing research or discoveries. The authors, editors and publishers cannot accept responsibility for errors or omissions or for any consequences from applications of the information in this site and make no warranty, expressed or implied, with respect to the contents herein.
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