Tuna oil contains EPA and DHA. Humans mainly consume EPA and DHA from fish oils and fats, with the highest content in fatty fish from the sea.

EPA and DHA are both unsaturated fatty acids (o-mega3), and their chemical names are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Both are unsaturated fatty acids, and the molecular structure is very close, so EPA is very easy to be converted into high-density lipoprotein (HDL) in the body to play a physiological function.

Fatty acids are an important component of fat, and their chemical structure is composed of long chains of carbon. The structure connecting the carbon and the carbon is called the key, fatty acids in the carbon and the carbon are connected to a bond called saturated fatty acids. All saturated fatty acids can be synthesized naturally in the human body and do not need to be supplemented from food. If there is a double bond between the carbon, then it is called an unsaturated fatty acid. The human body does not have the conditions to synthesize unsaturated fatty acids, should be supplied by food, so unsaturated fatty acids are also called essential fatty acids.