Linoleic Acid

Linoleic acid is an essential polyunsaturated fatty acid containing 18 carbon atoms and two cis double bonds. It is written in fatty-acid shorthand as 18:2 n-6, or 18:2 omega-6. The omega-6 designation means that the first double bond is located at the sixth carbon when counted from the methyl end of the fatty-acid chain .^1,2

Linoleic acid is essential because humans cannot synthesize it and must obtain it from the diet. Human fatty-acid metabolism lacks the enzymes needed to introduce the double bonds required to produce linoleic acid from fatty acids synthesized in the body. Once available, linoleic acid can be incorporated into complex lipids such as phospholipids, which are structural components of cell membranes .^2,3

Linoleic acid also serves as the parent fatty acid of the omega-6 family. Through elongation and desaturation reactions, it can be converted into longer-chain omega-6 fatty acids, including arachidonic acid. Linoleic acid and its downstream metabolites can also contribute to the formation of biologically active lipid molecules involved in cellular signaling .^2,3

Linoleic acid should not be confused with alpha-linolenic acid. Both are essential 18-carbon polyunsaturated fatty acids, but linoleic acid has two double bonds and belongs to the omega-6 family, whereas alpha-linolenic acid has three double bonds and belongs to the omega-3 family. These two fatty-acid families follow related but distinct metabolic pathways .^2,3