You mention that linoleic acid is the only truly essential fatty acid. Linolenic is an omega 3 fatty acid.

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On the nature of EFA’s, you mention that linoleic acid is the only truly essential fatty acid (EFA). While this may be so, it glosses over the effects of an undersupply of linolenic acid in the diet, because when eicosadienoic acid is synthesized and substituted for (gamma) linolenic acid in the w-3 eicosanoid pathways, the rates of peroxidation, cyclooxygenase activity, desaturase activity and reaction products are altered. Thus it seems very helpful to include both EFA’s in the diet for the proper functioning of the arachidonate/eicosanoid synthesis pathways in humans. (Not to mention the many journal articles on the triglyceride and LDL lowering effects of fish oils over the past several years) Is it sort of like the question of “folic acid or cobalamin“? To me, I would ask “why not both’?

The human body is supposed to be able to make some linolenic and most arachidonic fatty acids from linoleic acid. Previously, all three were considered essential fatty acids (EFA) before the metabolism of these fatty acids was understood.

Linoleic acid is found in butter, cocoa butter and coconut oil as well oils from corn, cottonseed, olive, palm, palm kernel, peanut, rapeseed (Canola), safflower, sesame, soybean, and sunflower. Butter, coconut, palm and palm kernel are saturated fats and the others are monounsaturated (olive and peanut) or polyunsaturated (corn, cottonseed, rapeseed, safflower, soybean, and sunflower. Sesame oil contains about equal amounts of mono and polyunsaturated fats.

Linolenic and arachidonic fatty acids are also found in these same food sources of fat.

The essential fatty acids found in fish oils are linolenic (18:3), timnodonic (20:5) and docosahexaenoic (22:6). Including two or three servings of broiled or baked fish per week in the diet has been recommended mostly because fish is generally lower in fat than red meats. Some fresh and salt-water fish are high in fat (trout and mackerel).

As to your comment about folic acid (important vitamin in the synthesis of new cells, especially during pregnancy to prevent neural tube defects) and cobalamin (vitamin B-12 which is important in the manufacture of red blood cells), their functions are equally important for which there are Recommended Dietary Allowances.

PS My “Ask the Dietitian” format is intended for the general public as a source of nutritional information, not a forum for scientists to debate in technical terms what only nutrition scientists understand. Most people want to know what to buy at the grocery store and how to eat healthy foods. Thank you for your comments.