Differential Effects of Omega-3 Fatty Acid, Docosahexaenoic Acid (DHA), In Animals and Humans

The omega-3 and omega-6 fatty acids are Essential Fatty Acids (EFAs) as their biosynthesis requires precursors: linoleic acid (LA; 18:2n-6), linolenic acid (ALA; 18: 3n-3); which can only be obtained through diet. Higher mammals cannot synthesize these precursors as they lack the enzymes (Δ9-, Δ12and Δ15desaturases) which are responsible for the synthesis of linoleic acid and linolenic acid, hence justifying their procurement through diet [1]. Docosahexaenoic acid (DHA, C22: 6) is the most abundant omega-3 polyunsaturated fatty acid in the brain [2]. DHA along with Arachidonic Acid (AA, C20: 4) constitute the major polyunsaturated fatty acids in the brain. The half-life of DHA in blood of healthy human subjects is 20 ± 5.2 hours [3] and 22.4 ± 2.9 hours in brain phospholipid which is much longer than that of AA (3.79 ± 0.12 hours) implicating a preferential incorporation of DHA into brain phospholipids [4]. DHA is present as a component in all membranes and hence has a potential role in virtually all systems of the human body. This mini-review outlines some of the beneficial effects of DHA in animal models and humans and the differences in its effects with age.