Diets
should contain 18:2n-6 (linoleic acid) and 18:3n-3 (alpha-linolenic
acid) which are subsequently converted to the metabolically
essential C20 and C22 homologues, 20:4n-6 (arichidonic acid,
ARA), 20:5n-3 (eicosapentaenoic acid, EPA) and 22:6n-3 (docosahexaenoic
acid, DHA).