 There are three types of omega-3 fatty acids; namely alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).Alpha-linoleic acid is an essential fatty acid, and is the form that is most common and widespread of the omega-3 fatty acids.Vegan sources of ALA include plant oils, nuts, flaxseed (linseed), and soy.