Omega-3 fatty acids are a group of polyunsaturated fats -- alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) -- that are found in fish, nuts, seaweed and vegetables. Research has linked omega-3 consumption to heart health and mental benefits, most of which can be attributed to the fatty acids' DHA and EPA components. You can get the moderate doses that appear to reduce heart disease by eating 3.5 ounces of fatty fish two to five times per week. Higher doses used to lower triglycerides, or reduce attention deficit and hyperactivity disorder or depression, are more easily met using an omega-3 supplement.
The main types of omega-3 supplements are fish oil, cod liver oil, krill oil, algae or algal oil and flaxseed oil. Rich in both EPA and DHA, fish oil is the most common. Cod liver oil is also high in EPA and DHA, but when taken in large doses can provide too much of the vitamins A and D. Made from small shrimplike crustaceans, krill oil can potentially cause an allergic reaction in people with a shellfish allergy. As for vegan options, algae oil is rich in DHA while flaxseed oil contains only ALA. Some ALA can be converted to EPA and DHA in the body, but it's a very small amount.
Also available is a prescription-only fish oil called Lovaza (omega-3-acid ethyl esters) that has a high concentration of EPA and DHA. Its manufacturer, GlaxoSmithKline, has had to prove to the Food and Drug Administration (FDA) through multiple studies that Lovaza is safe and effective. Over-the-counter omega-3 supplements are also regulated by the FDA, but instead of manufacturers having to prove that products are safe before they reach the market, the burden lies on the FDA to prove if they're unsafe later.
Food still remains the best way to increase your omega-3 intake. Not only are sources of omega-3s also high in vitamins and minerals, but by choosing to eat more fish and vegetables, you may get other healthful benefits.