Universal Nutrition Fish Oil is the most important source of essential fats that the body needs and cannot be synthesized by the body. It is extracted from fish oils such as sardines, anchovies, herring and mackerel, which contain long-chain fatty acids such as docosahexaenoic acid (DHA) and iscosapentaenoic acid (EPA). They are omega-3 fatty acids needed for metabolism and play important roles in brain function, heart and immune function, joint health, normal hormone formation, and maintenance of the nervous system.