Eicosapentaenoic acid (more commonly known as EPA; C20H30O2, all-cis-fatty acid 20:5 omega-3) is a polyunsaturated fatty acid that acts as a precursor for prostaglandin-3 (makes blood platelets less sticky) and thromboxane-3 groups. It is found in fish oils of cod liver, herring, mackerel, salmon, sardines. It is also found in human breast milk.