Essential Fatty Acids in Clinical Medicine

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Abstract
There are two types of essential fatty acids (EFAs), the n-6 derived from linoleic acid and the n-3 from alpha-linolenic acid. They play major roles in the structure of all organs and determine some of the properties of all membranes. The EFAs also act as precursors for the eicosanoids, the prostaglandins and leukotrienes. The body requires adequate intakes of linoleic and alpha-linolenic acids but must also be able to metabolize them normally. Abnormalities of EFA intake and absorption are exceedingly rare except in patients with known malabsorption or who are on total parenteral nutrition. Abnormalities of EFA metabolism, in contrast, appear to be rather common. Patients with atopic eczema seem to have a defect at the delta-6-desaturase level which leads to elevated blood levels of the two main dietary precursors but significantly reduced levels of all metabolites. Patients with premenstrual syndrome appear to have low n-6 metabolites and elevated n-3 metabolites, those with premenstrual breast disease to have low n-6 and near normal n-3 metabolites and those with non-cyclic breast disease to have a deficiency of both n-6 and n-3 acids. Both diabetes and alcoholism lead to defective delta-6–desaturase function and low concentrations of EFA metabolites. There is considerable clinical evidence that gamma-linolenic acid can correct some of the abnormalities in EFA patterns and can also lead to simultaneous clinical improvement, suggesting that the EFA abnormalities are playing a causative role. As Sinclair predicted 30 years ago, understanding of EFA metabolism seems likely to bring about major practical advances in clinical medicine.