Omega-3 and Omega-6 Fatty Acids

Within the broader category of unsaturated fats, two specific families attract particular attention because of their health effects: fatty acids containing an omega-3 double bond and fatty acids containing an omega-6 double bond. The naming convention counts carbons from the 'omega' end of the chain -- omega denoting the last carbon of the fatty-acid chain, the one furthest from the -COOH (carboxylic acid) end. An omega-3 fatty acid is one whose first C=C double bond falls between the third and fourth carbon counted from that omega end; an omega-6 fatty acid, by the same counting convention, has its first double bond at the sixth carbon from the omega end. The chapter's worked example is linolenic acid, systematically named 9,12,15-octadecatrienoic acid: an 18-carbon chain running from the alpha carbon (next to -COOH) to the omega carbon (the terminal methyl carbon), carrying three C=C double bonds at positions 9, 12 and 15 when numbered from the carboxyl end -- which, renumbered from the omega end instead, places the first double bond between the third and fourth carbon, confirming it as an omega-3 fatty acid. The health effects of the two families differ: omega-3 fats have been found to raise the level of high-density lipoprotein ( …