a-Linolenic acid (ALA) is an n-3 fatty acid, it is one of two essential fatty acids (EFAs), so called because they are necessary for health, and they cannot be produced within the human body. They must be acquired through diet. ALA is an omega-3 fatty acid found in seeds (chia, flaxseed, see also table below), nuts (notably walnuts), and many common vegetable oils. In terms of its structure, it is named all-cis-9,12,15-octadecatrienoic acid. In physiological literature, it is listed by its lipid number, 18:3, and (n-3); its isomer GLA is 18:3 (n-6).