Gamma-linolenic acid

Encyclopedia : G : GA : GAM : Gamma-linolenic acid

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Gamma-linolenic acid (GLA) is an omega-6 fatty acid that exists primarily in plant fats. In physiological literature, it is given the name 18:3 omega-6. Its systematic chemical name is all-cis-6,9,12-octadecatrienoic acid). Chemically, GLA is a carboxylic acid with an 18-carbon chain and three cis double bonds; the first double bond is located at the sixth carbon from the omega end. It is also sometimes called gamolenic acid.

GLA is a precursor of prostaglandin E1, very active biologically regulating such functions as the vessel and immune systems.

The "omega" fatty acids are very beneficial to health. A common misconception is that most people lack both omega-3 and omega-6 fatty acids in their diets, but in fact most people only require more of the omega-3 fatty acids found in most fish and some nuts, seeds, and vegetables (for example, walnuts, flax, purslane). Studies have shown that the average person consumes up to 10 times their required daily intake of omega-6 fatty acids.

The chemical strucuture of GLA showing physiological numbering (red) and chemical numbering (blue) conventions.

Sources

GLA is usually found in oenothera (evening primrose oil, blackcurrant seed oil, borage oil and hemp seed oil. Each contains varying amounts of the fatty acid, with borage oil usually being the most heavily concentrated form. All four oils can be found on the shelves in most pharmacies.

From all the other sources of GLA, that in evening primrose oil appears to be the most biologically active. This seems to be because most of the GLA is in the form of enotherol, a particular triglyceride consisting of two molecules of linoleic acid (LA) and one of GLA on a glycerol backbone. It has been suggested that in enotherol, GLA is in its most readily metabolisable form.

Basically, the body turns GLA into another form, dihomo-gamma-linolenic acid (DGLA), which is a precursor in the production of prostaglandins. Prostaglandins have a variety of roles in maintaining normal body function.

The belief that most people lack GLA is incorrect. GLA is produced by the body naturally from LA. Not to be confused with linolenic acid which is the omega-3 fatty acid found in flax seed. The LA is consumed sufficiently in most diets, from such abundant sources as cooking oils and meats. A lack of GLA can occur when people grow older and their bodies become unable to produce it in sufficient quantities, or due to specific dietary deficiencies.

GLA can also form a lithium salt, increasing its solubility in water. The resulting compound is Li-GLA, also called lithium gamma-linolenic acid or lithium gammalinolenate. Li-GLA is currently in phase II clinical trials to determine whether it is useful in the treatment of HIV infections, since it has the ability to destroy HIV-infected T cells in vitro. It has a number of side-effects, including a reduction in hemoglobin, hematuria, gastrointestinal disturbance, fatigue and headache.

Benefits

Although GLA is an ω-6 fatty acid (which are generally pro-inflammatory) it is reported to have anti-inflammatory properties; see discussion at Essential fatty acid interactions#The paradox of dietary GLA.

As to health benefits, GLA is sometimes prescribed in the belief that has anti-inflammatory properties lacking some of the common side effects of other anti-inflammatory drugs. Herbal medicine advocates recommend GLA for autoimmune disorders, arthritis, eczema and PMS with noticeable results not expected for months. Research is ongoing, investigating GLA as a potential anticancer agent. Conflicting data is found for GLA in the treatment of eczema.^{[[Citing sources citation needed]]} It is strongly advised that people should not take GLA together with anticonvulsant medication. It is also discouraged to take GLA over any sort of long term due to studies showing that it can lead to inflammation and other problems.^{[[Citing sources citation needed]]} GLA is unique among the omega-6 polyunsaturated fatty acids (linoleic acid, GLA and arachidonic acid) in its potential to suppress tumor growth and metastasis. (Fan 1998)

History

In the Middle Ages, a folk remedy would be to take borage for any problems from rheumatism to heart disease.

There is no β-linolenic acid; it turned out to be an artifact of the original analytical process. (Gunstone)

References

• [Essential fatty acid metabolism and its modification in atopic eczema] American Journal of Clinical Nutrition, Vol. 71, No. 1, 367S-372s, January 2000.

• [British Medical Journal summary of current findings on Evening Primrose Oil in the treatment of eczema]

• [Obituary of David Horrobin] - passionate promoter of evening primrose oil and author of the American Journal Clinical Nutrition report cited above.

• [Primrose Oil and Eczema: How Research Was Promoted and Suppressed] Critical summary on Quackwatch of research on and marketing for evening primrose oil.

• [British Medical Journal: Efficacy and tolerability of borage oil in adults and children with atopic eczema].

• Fan, Yang-Yi and Chapkin, Robert S. [Importance of Dietary gamma-Linolenic Acid in Human Health and Nutrition] A review article at The American Society for Nutrition; 9 September 1998. URL Retrieved 3 February 2006
• Gunstone, Frank, [Personal Communication] at Peter Lapinskas' pages; URL Retrieved 3 February 2006

See also

• Linolenic acid

 

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