Horrobin, D.F. and Manku, M.S.
The seed oil of the evening primrose (Oenothera biennis): a new oilseed crop
In: Brooker, S.G.; Renwick, A.; Hannan, S.F.; Eyres, L. (Eds.) Fats for the Future. Duromark, Auckland, NZ. 1983: 99-101.


The seed oil of the evening primrose (Oenothera biennis) is very similar to safflower oil in most respects. However the primrose oil contains a variable percentage of gamma-linolenic acid, a fatty acid not found in other commonly used vegetable oils. Gamma-linolenic acid (GLA) is the first essential fatty acid metabolite of linoleic acid. Evidence is presented to suggest that a functional essential fatty acid deficiency is common in humans, not because of a lack of dietary linoleic acid but because of inadequate conversion of linoleic acid to GLA. Patients with hypercholesterolaemia appear to convert less than 1% of dietary linoleic acid to GLA. Individuals with atopic disorders and with illnesses associated with atopy such as cyclic (premenstrual) breast disease appear to have an inherited defect in their ability to form GLA. Aging, diabetes and alcohol all inhibit the delta-6-desaturase enzyme which forms GLA. There are thus many reasons why GLA may be beneficial to human health. A strain of Oenothera biennis has been developed which gives a consistent GLA content in the oil (Efamol). Efamol has been tested in a variety of placebo-controlled, double blind studies and been shown to cause lowering of cholesterol, to improve atopic eczema and cyclical breast disease, to attenuate the effects of alcohol and to treat Raynaud's syndrome. GLA, a precursor of prostaglandin (PG) E1, is likely to be of value in conditions such as Raynaud's syndrome which have been shown to respond to PGE1 infusions.

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