There are three types of omega-3 fatty acids: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Plant foods and supplements including flaxseed, walnuts and beans, as well as canola, soybean and flaxseed oils contain ALA. Fish, including mackerel, tuna, salmon, herring, and trout, as well as some algae, contain EPA and DHA. Most health benefits are thought to come from EPA and DHA. Your body converts the ALA in plant foods into EPA and DHA, but there is some debate over whether the converted EPA and DHA offer the same level of benefits as when these fatty acids are consumed directly from seafood.
All of these foods can be part of a healthy diet. Omega-3 supplements from fish or plant foods may also be recommended if you have certain conditions or if you can't consume these foods. Talk to your doctor before taking any supplements about whether increasing your intake of these foods and/or taking supplements is right for you.