Omega-3 acids are found in flaxseed oil, walnut oil, and marine plankton and fatty fish. The predominant fatty acids found in fatty fish and fish oils are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The most beneficial and active of these fatty acids are EPA and DHA.

In the early 1970s Danish physicians observed that Greenland Eskimos had an exceptionally low incidence of heart disease and arthritis despite the fact that they consumed a high-fat diet. Research discovered that two of the fats (oils) they consumed in large quantities, EPA and DHA, were highly beneficial. Recent research established that EPA and DHA play a role in the prevention of atherosclerosis, heart attack, depression, and cancer. Clinical trials have shown that fish oil supplementation is effective in the treatment of many disorders including rheumatoid arthritis, diabetes, ulcerative colitis, and Raynaud's disease.

An enormous amount of medical literature testifies to the fact that fish oils prevent and may help to ameliorate or reverse atherosclerosis, angina, heart attack, congestive heart failure, arrhythmias, stroke, and peripheral vascular disease. Fish oils help maintain the elasticity of artery walls, prevent blood clotting, reduce blood pressure and stabilize heart rhythm. Several clinical trials have confirmed that fish oils are effective in lowering high blood pressure and that they may work even better if combined with a program of salt restriction.

Fish oils have also been shown as effective in reducing inflammation and can assist people suffering from rheumatoid arthritis or ulcerative colitis. There is also evidence that fish oil consumption can delay or reduce tumor development in breast cancer. Taking a daily supplement of fish oils of as little as 2.5 grams has been found effective in preventing the progression from benign polyps to colon cancer.

Cod liver oils and fish oils are not the same. Cod liver oil is extracted from cod liver and is an excellent source of vitamins A and D. Fish oils are extracted from the flesh of fatty fish like salmon and herring and are good sources of EPA and DHA.