Chain Lengths & Metabolism
Metabolism of omega-3 and omega-6 EFA converts the 18-carbon polyunsaturated fatty acids (PUFA) that are abundant in foods to long chain 20- and 22-carbon highly unsaturated fatty acids (HUFA) that accumulate in cell membranes. The number notations (e.g., 18:3n-3) indicate the carbons in the chain and the number of double bonds in the n-3 or n-6 structures.
The balance of n-3 and n-6 HUFA in tissues is linked to dietary intakes. The balance affects the intensity of many physiological actions that convert the HUFA into active hormone-like eicosanoids that control our physiology.
The balance of n-3 & n-6 HUFA chains is a health risk assessment value.
These structures of the different omega-6 EFA show how the fatty acid chain grows longer and more double bonds are added during metabolism of linoleic acid, the most abundant essential fatty acid in American foods.
The asterisk shows where the additional double bond occurs in the chain of the corresponding, competing omega-3 EFA that are formed from alpha-linolenic acid, the major omega-3 nutrient in plants. Foods from the oceans, lke fish and shellfish, may contain appreciable amounts of all of the indicated omega-3 nutrients.