Fish oil can be obtained by eating fish or taking supplements. Fish that are especially rich in the beneficial oils known as omega-3 fatty acids include mackerel, herring, tuna, and salmon. Two of the most important omega-3 fatty acids contained in fish oil are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Some fish oil products are approved by the US Food and Drug Administration (FDA) as prescription medications to lower triglycerides levels. Fish oil is also available as a supplement. Fish oil supplements do not contain the same amount of fish oil as prescription products, so they cannot be used in place of prescription products. Fish oil supplements are sometimes used for heart health and mental health, but there is no strong evidence to support most of these uses. Do not confuse fish oil with EPA, DHA, cod liver oil, flaxseed oil, krill oil, or shark liver oil. See the separate listings for these ingredients.