The Omega-3s are essential polyunsaturated fatty acids. The human body can not synthesize the Omega-3s from other substances, so you must get these important nutrients from the foods you eat and supplements you consume. EPA and DHA are the most important, long-chain Omega-3s. EPA and DHA are naturally found in marine sources, including fatty fish – salmon, tuna, mackerel, herring – shellfish, and marine algae.