Like most vitamins, essential fatty acids cannot be manufactured by the body and must be obtained through dietary sources. It is considered essential because it cannot be manufactured by the human body. AA contains 20 carbons and 4 double bonds. It is the brain's principal omega-6 fatty acid.
Arachidonic acid is found primarily in animal fats and is often too high in modern diets.
This fatty acid can be converted into the powerful locally acting hormones, prostaglandins. One example is PGE2, which has inflammatory activity. PG and related substrances are involved in many other biological processes from gene expression to blood clotting. Alpha-linolenic acid, EPA, and DHA can counter the effects of arachidonic acid. It is the most important omega-3 fatty acid found in the brain and in highly concentrated in the retina.