Fish oil is a rich source of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), omega-3 fatty acids. Fish oil seems to protect against heart attack, stroke, cancer and inflammatory diseases like rheumatoid arthritis. It is involved in protection against disease in several ways. The most important include "thinning" the blood and preventing blood clots, and being converted into less inflammatory prostaglandins and reducing inflammation. Oily fleshed, cold water fish like salmon and sardines are the best sources of fish oil, although pharmaceutical grade fish oil capsules are available and may be used if higher amounts are needed for specific conditions. If you use fish oil capsules, choose a product that is free from heavy metals and toxins that may also contaminate fish. Read more about pharmaceutical grade fish oil, or explore articles regarding omega 3 fish oil.