Essential Fatty Acid Interactions

Essential Fatty Acid Interactions

The actions of the ω-3 (omega-3) and ω-6 (omega-6) essential fatty acids (EFAs) are best characterized by their interactions; they cannot be understood separately.

Arachidonic acid (AA) is a 20-carbon ω-6 conditionally essential fatty acid. It sits at the head of the "arachidonic acid cascade" – more than 20 different signalling paths that control a wide array of bodily functions, but especially those functions involving inflammation and the central nervous system. Most AA in the human body derives from dietary linoleic acid (another essential fatty acid, 18:2 ω-6), which comes both from vegetable oils and animal fats.

In the inflammatory response, two other groups of dietary essential fatty acids form cascades that parallel and compete with the arachidonic acid cascade. EPA (20:5 ω-3) provides the most important competing cascade. It is ingested from oily fish or derived from dietary alpha-linolenic acid found in, for instance, hemp oil and flax oil. DGLA (20:3 ω-6) provides a third, less prominent cascade. It derives from dietary GLA (18:3 ω-6) found in, e.g. borage oil. These two parallel cascades soften the inflammatory effects of AA and its products. Low dietary intake of these less inflammatory essential fatty acids, especially the ω-3s, is associated with a variety of inflammation-related diseases.

Today, the usual diet in industrial countries contains much less ω-3 fatty acids than the diet of a century ago. The diet from a century ago had much less ω-3 than the diet of early hunter-gatherers. We can also look at the ratio of ω-3 to ω-6 in comparisons of their diets. These changes have been accompanied by increased rates of many diseases – the so-called diseases of civilization – that involve inflammatory processes. There is now very strong evidence that several of these diseases are ameliorated by increasing dietary ω-3, and good evidence for many others. There is also more preliminary evidence showing that dietary ω-3 can ease symptoms in several psychiatric disorders.