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Evening Primrose Oil

Evening Primrose

The beautiful evening primrose flower blooms for a single day, but its seed oil helps you bloom year after year. Evening primrose oil (EPO) is a rich source of the essential fatty acid, gamma-linolenic acid (GLA), which acts as a building block for making beneficial prostaglandins. Unlike other dietary omega-6 fatty acids, GLA is converted into Series 1 prostaglandins (i), which relax blood vessels, lower blood pressure, decrease inflammation, improve nerve function and circulation, as well as regulating calcium metabolism. GLA also prevents the release of arachidonic acid from cells, which, in turn, reduces production of Series 2 prostaglandins from are involved in unwanted blood clotting and inflammation.

While your body can make small amounts of GLA, this process is easily blocked by factors such as increasing age, smoking, pollution, lack of certain vitamins and minerals or excessive intakes of saturated fat, sugar or alcohol.


If your skin is lacking in essential fatty acids, it becomes scaly, rough, itchy, prematurely wrinkled and dry. It also becomes more prone to spots as oil gland ducts become distorted and trap grease. Evening primrose oil can reduced the symptoms of eczema, with the greatest improvement seen in the level of itching (ii).


Essential fatty acids can reduce inflammation in rheumatoid arthritis. In one trial, 60% taking GLA were able to stop NSAID therapy completely, while another 25% were able to cut their NSAID dose in half. Interestingly, taking both evening primrose and fish oils together was only slightly more effective than taking EPO alone (iii). Later studies using higher doses found GLA was able to reduce the number of joints that were tender or swollen (iv),(v).

Hormone balance

Evening primrose oil provides building blocks for making sex hormones, and some evidence suggests it is helpful in premenstrual syndrome (vi). One study found supplements relieved bloating and mastalgia in 95% of women, irritability in 80%, low mood in 74%, swollen peripheries in 79% and anxiety in 53% (vii). Some women also find it helpful for hormone balance around the time of the menopause, although few trials have investigated this.


A pilot study involving men with benign prostate enlargement showed improvement in urinary frequency. Before treatment, urinary frequency averaged 14.8 times per day and 4.8 times per night. After taking evening primrose oil for 6 months, daytime frequency reduced to 9.8 and nocturia to 2.2. It appears to work by suppressing conversion of testosterone to dihydrotestosterone within prostate cells (viii).

  • How much do you need?

    An ideal intake is 500mg - 1000mg EPO per day (equivalent to 40mg to 80mg GLA) for preventive health.

    Up to 3000mg (equivalent to 240mg GLA) per day to help breast pain, pre-menstrual syndrome or menopausal symptoms - may take up to 3 months to notice a beneficial effect.

  • Caution

    The only people who should not take EPO are those with a rare form of epilepsy, known as temporal lobe epilepsy, and people taking medication for schizophrenia.

  • References and links

    (i)    Belch JJ, Hill A. 2000 Evening primrose oil and borage oil in rheumatologic conditions. Am J Clin Nutr 71(1 Suppl):352S-6S
    (ii)   Morse PF et al. 1989. 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. Br J Dermatol.;121:75–90.
    (iii)  Belch, J. et al. 1988. Effects of altering dietary EFAs on requirements for NSAIDs in patients with rheumatoid arthritis: a double blind, placebo controlled study. Annals Rheum Disease, 47:96-104.
    (iv)   Leventhal, L. et al. 1993. Treatment of rheumatoid arthritis with GLA. Annals Intern Med, 119:867-73.
    (v)    Zurier, R. et al. 1996. Gamma-Linolenic acid treatment of rheumatoid arthritis. A randomized, placebo-controlled trial. Arthritis Rheum, 39:1808-17.
    (vi)   Horrobin DF et al. 1991. Abnormalities in plasma essential fatty acid levels in women with premenstrual syndrome and with non-malignant breast disease. J Nutr Med.2:259–264
    (vii)  Larsson B, Jonasson A, Fianu S 1989. C urrent Therapeutic Research, 46 (1):58-63.
    (viii) Pham H, Ziboh VA 2002. 5-alpha-reductase-catalyzed conversion of testosterone to dihydrotestosterone is increased in prostatic adenocarcinoma cells: suppression by 15-lipoxygenase metabolites of gamma-linolenic and eicosapentaenoic acids. J Steroid Biochem Mol Biol. 82(4-5):393-400.

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