Fig. (1) Biosynthesis of the omega-3 and omega-6 families of Polyunsaturated Fatty Acids in human: For essential fatty acids LA and ALA, this includes a series of reactions of desaturation (addition of double bonds) and elongations (addition of two carbon atoms). Key: Delta-5 desaturase (FADS1), Delta-6 desaturase (FADS2), elongases (ElovL2, Elov5). AL (Linoleic acid), DGLA (dihomo-γ-linolenic acid) AA (Arachidonic acid). ALA (alpha-Linolenic acid), EPA (Eicosapentaenoic acid), DPA (Docosapentaenoic acid) and DHA (Docosahexaenoic acid).