What is fish oil?
Fish oil is a dietary source of omega-3 fatty acids — substances your body needs for many functions, from muscle activity to cell growth.

Omega-3 fatty acids are derived from food. They can’t be manufactured in the body. Fish oil contains two omega-3s called docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Dietary sources of DHA and EPA are fatty fish, such as salmon, mackerel and trout, and shellfish, such as mussels, oysters and crabs. Some nuts, seeds and vegetable oils contain another omega-3 called alpha-linolenic acid (ALA).