Article Commentary: The Emerging Role of Eicosapentaenoic Acid as an Important Psychoactive Natural Product: Some Answers but a Lot more Questions

Omega-3 polyunsaturated fatty acids play important roles in both the structure and communication processes of cells. Dietary defi ciences of these fatty acids have been implicated in cardiac dysfunction, cancer and mood disorders. In the latter, clinical trials have strongly suggested that not all types of omega-3 PUFA are equally effi cacious. In particular eicosapentaenoic acid (EPA) appears to be the most useful in ameliorating the symptoms of major depressive disorder. The mechanism by which omega-3 PUFA have these effects, and why EPA is apparently more effective in this role than the much more abundant brain lipid docosahexaenoic acid, is unclear. The available data do suggest various biologically plausible mechanisms all of which are amenable to study using straightforward experimental approaches. To progress further, a bet- ter understanding of how EPA and other omega-3 PUFA effect neurophysiological and neurosignalling processes is required. Background (n-3) polyunsaturated fatty acids (PUFA) are nutritionally important molecules normally found incorporated into either triglycerides or membrane phospholipids. The smallest omega-3 PUFA, 18 carbon alpha linolenic acid (ALA) must be acquired nutritionally but its metabolites, 20 carbon eicosapentaenoic acid (EPA) and 22 carbon docosahexaenoic acid (DHA), can be synthesised by cells. The rate of conversion of ALA into longer omega-3 PUFA is, however, rather slow and nutritional intake plays a large part in determining the abundance of EPA and DHA in the membrane (Emken et al. 1994). The other major PUFA class are omega-6 (n-6), for example, 20 carbon arachidonic acid (AA). The number refers to the location of the fi rst C = C double bond relative to the omega (terminal) carbon atom.