Does the body require essential fatty acids for good health? The term _essential_ implies that a nutrient is required for the body to work properly and that the consequences of deficiency are serious. Examples are the 13 essential vitamins and the essential amino acids. What evidence shows that "essential fatty acids" (EFAs) are just as essential? What defines a "deficiency"? Please emphasize evidence for **ALA** (n-3 linolenic acid). 2004 PubMed article claims, > First it was shown that the differentiation and functioning of cultured brain cells requires omega-3 fatty acids. It was then demonstrated that alpha-linolenic acid ( **ALA** ) deficiency alters the course of brain development, It unfortunately it does not give us numbers for how much ALA is required or what exactly constitutes a deficiency. Can anyone find these?

According to Metabolism of α-linolenic acid in humans _Prostaglandins, Leukotrienes and Essential Fatty Acids_ vol. 73, pages 161–168.

> α-Linolenic acid (18:3n-3) is one of the two polyunsaturated fatty acids (PUFA) which are essential in the human diet. It is difficult to ascribe specific functional effects directly to 18:3n-3 and the low concentrations of this fatty acid in most mammalian cell membranes, with the exception of skin, suggest that it is unlikely to exert direct effects on cell and tissue function [reference 1]. However, the essentiality of 18:3n-3 may lie primarily in it being a substrate for the synthesis of the long-chain, more unsaturated PUFA eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3)

where reference 1 is What is the role of α-linolenic acid for mammals? _Lipids_ , 37 (2000), pp. 1113–1123