A type of fat, found in oily fish and in some plant-based foods, that is thought to have beneficial effects on health. Omega-3 fatty acids called eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found abundantly in cold-water fish such as mackerel, salmon, herring, tuna, and halibut. Sources of a third type, alpha-linolenic acid (ALA), include walnuts, flaxseed, and canola oil.
EPA and DHA have been studied more than ALA. Studies show that some people with rheumatoid arthritis (RA) who eat EPA and DHA have modestly reduced pain and joint tenderness, although it can take several months. In some cases, taking fish oils has allowed people to cut their doses of nonsteroidal anti-inflammatory drugs. Fish oils may also be useful in easing the symptoms of other arthritis-related conditions, such as psoriatic arthritis and Raynaud phenomenon, although less research has been done on this. In addition, all omega-3 fatty acids, and especially those from fish, may reduce blood pressure and blood levels of triglyceride (a fat that circulates in the bloodstream), lowering the risk of heart disease.
To get enough omega-3s in your diet, the Food and Drug Administration and the American Heart Association recommend eating oily fish at least twice a week. Fish oils are also available as supplements. Possible side effects include gastrointestinal upset and breath that smells of fish. Don’t take fish oil supplements without talking to your doctor because they can interact with other drugs. For example, if you take both anticoagulant (blood-thinning) medicines and omega-3 supplements, you can end up bleeding excessively.