The LC-PUFA are comprised of 20 or more carbon atoms and three or more double bonds. They are classified as omega-3 or omega-6, based on the location of the last double bond in relation to the terminal methyl end of the molecule. LC-PUFA are synthesized from the parent omega-3 and omega-6 essential fatty acids, α-linolenic acid and linoleic acid, which are converted to omega-3 and omega-6 LC-PUFA, respectively, through a process of enzymatic desaturation and elongation. In the omega-3 series, α-linolenic acid is converted to the LC-PUFA, eicosapentaenoic acid (EPA), which may in turn be converted to docosahexaenoic acid (DHA). Similarly, in the omega-6 series, linoleic acid is converted to arachidonic acid (Figure 1). α-linolenic acid and linoleic acid are essential fatty acids, meaning that they cannot be synthesized by the human body. Fatty acids in the omega-3 and omega-6 series cannot be interconverted. Dietary sources of α-linolenic acid, the precursor of DHA and EPA, include walnuts, rapeseed and flaxseed oils, and green leafy vegetables. However, because of the relative inefficiency of this conversion process in humans, most of the omega-3 LC-PUFA are obtained from dietary ingestion of fish and seafood.
Expert Rev of Obstet Gynecol. 2010;5(1):125-138. © 2010
Cite this: Role of Omega-3 Fatty Acids in Maternal, Fetal, Infant and Child Wellbeing - Medscape - Jan 01, 2010.