There are three main omega-3 fatty acids: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is an essential fatty acid that your body doesn’t make on its own, so you have to get it from your diet. Although it is possible for your body to convert some ALA into EPA and then to DHA, it can only do so in limited amounts. Eating EPA- and DHA-rich foods is a great way to increase levels of these omega-3 fatty acids in your body. Omega-3s also help give your body energy and have many functions in your heart, blood vessels, lungs, immune system, and endocrine system (the network of hormone-producing glands).