Gamma Linolenic Acid (GLA)
Gamma linolenic acid (GLA) is a highly unsaturated fatty acid made in the human body from other essential fatty acids. The main sources of GLA are oils of evening primrose, borage, and black currant plants (see Evening Primrose). Many commercial preparations sell these extracts as GLA. It is also found in human breast milk.
GLA is found naturally to varying extents in the fatty acid fraction of some plant seed oils. In evening primrose seed oil, it is present in concentrations of 7 to 14% of total fatty acids; in borage seed oil, 20 to 27%; and in blackcurrant seed oil, 15 to 20%. GLA is also found in some fungal sources. GLA is produced naturally in the body as the delta 6-desaturase metabolite of the essential fatty acid linoleic acid. Under certain conditions, e.g. decreased activity of the delta-6 desaturase enzyme, GLA may become a conditionally essential fatty acid. GLA is present naturally in the form of triacylglycerols (TAGs). The stereospecifity of GLA varies among different oil sources. GLA is concentrated in the sn-3 position of evening primrose seed oil and blackcurrant seed oil and in the sn-2 position in borage seed oil. GLA is concentrated evenly in both the sn-2 and sn-3 positions of fungal oil.
The anti-inflammatory and anti-aggregatory actions can be accounted for by reviewing its role in eicosanoid biosyntheses. GLA is a precursor in the synthesis of prostaglandin E1 (PGE1) as well as the series-3 prostaglandins. It also serves as a precursor in the synthesis of eicosapentaenoic acid (EPA). EPA is a precursor of the series-3 prostaglandins, the series-5 leukotrienes and the series-3 thromboxanes. These eicosanoids have anti-thrombogenic, anti-inflammatory and anti-atherogenic properties. PGE1 inhibits platelet aggregation and has a vasodilation action. The incorporation of GLA and it metabolites in cell membranes may also play a role in the possible anti-inflammatory and anti-proliferative actions of GLA.
GLA appears to be effective in some cases of rheumatoid arthritis and may be indicated in some other inflammatory disorders, such as Sjogren's syndrome and ulcerative colitis. Possible other indications include diabetic neuropathy, acute respiratory distress syndrome, hypertension and elevated serum lipids. GLA has been used with some success in some cancers, principally cerebral gliomas. It has not proved useful for tardive dyskinesia, premenstrual syndrome or menopausal flushing. It may be indicated in some cases for atopic eczema and atopic dermatitis, particularly to help with itching, as well as for uremic skin conditions in hemodialysis patients. It should probably not be used in efforts to enhance immunity as it may be immunosuppressive.