Linoleic acid is obtained from the desaturation of oleic acid in plants. Because the desaturation ability of mammals is limited, it is impossible to introduce double bonds on carbon atoms other than C-9, while plant cells do not have such restrictions, so the double bonds at linoleic acid 12- position cannot be introduced in animals, but only in plant cells. Therefore, linoleic acid is called essential fatty acid, which must be obtained from food and cannot be synthesized by itself or rarely.

In animals, linoleic acid (18:2n-6) is firstly metabolized to γ -linolenic acid (18:3n-6) by δ6- desaturase (rate-limiting enzyme), and then γ -linolenic acid extends to dihomo-γ-linolenic acid (20:3n-6). Arachidonic acid (20:4n-6) is desaturated from dihomo-γ-linolenic acid, which can be further converted into prostaglandin and leukotriene.