It's complicated; it's chemistry! A fatty acid is an organic compound composed of a carbon chain with hydrogens attached and an acid group at one end. A polyunsaturated fatty acid has two or more double bonds. Omega is used by chemists to refer to the position of the first double bond found in the chain, and are numbered accordingly. Thus, we refer to the Omega "oils" or fats that are essential to human physiology by numbers.
The Omega of focus is the Omega-3, or "alphabet soup." EPA (eicosapentanoic acid), DHA (docosahexanoic acid) and ALA (alpha-linolenic acid). EPA and DHA come from fish, and ALA comes from plants (flax, nuts, soybeans, etc). Plant based ALA must be converted to EPA to become active, and is less potent. Women seem to be metabolically better at converting ALA to EPA than men.
Why are they so important? They decrease clotting and lower triglycerides, reducing the risk of cardiovascular disease. They have also been shown to curb the risk of an irregular heart beat, or arrythmia. The brain is also rich in DHA and studies have shown improved symptoms in people with major depression. Incidence of macular degeneration (blindness) is shown to be 25% less in people who eat fish. They are also an anti-inflammatory; helping to relieve symptoms of arthritis and allergies. Studies are currently underway to find if they lower the risk of rheumatoid arthritis and other autoimmune diseases. Omega-3's are essential for fetal brain and kidney development, so it is vital for pregnant women to get enough.
Omega-3 fatty acids are found in cold water fatty fish - salmon (NOT farm raised), herring, mackerel, tuna, trout, and sardines. The American Heart Association recommends two servings (4-6 oz. ea.) per week. That supplies about 400 to 500 mg. of EPA & DHA per day (fat based nutrients stay in our bodies longer). Fish oil-in-a-pill may only contain about 30% EPA & DHA, so read the label. Ignore the other omega's in the bottle of fish oil supplements - you don't need them. They're plentiful in the diet. Consumer Reports claim all major brands are mercury-free. As for the mercury in fish, usually the larger and "older" fish contain more, so avoid sea bass and shark. Cod liver oil is not recommended as a supplement since the liver is a filter; the mercury is concentrated in that organ. Nutrients in other foods we eat (especially broccoli) help to detox heavy metals found in our environment, so don't be afraid of sea food. Look for other foods now fortified with omega-3's such as margarines, eggs (Eggland's Best), soy milk, orange juice, peanut butter...
If you have risk factors for heart disease such as high triglycerides, or if you are pregnant or breast feeding, talk to your doctor or a dietitian about an appropriate supplement.
~National Eye Institute, Bethesda, MD