The fat in fish contains a class of polyunsaturated fatty acid called omega-3's. These fatty acids differ from the polyunsaturated fatty acids found in vegetable oils, called omega-6's, and have different effects on the body. (Fish do not manufacture such fats but obtain them from the plankton they eat; the colder the water, the more omega-3's the plankton contains). The two most potent forms of omega-3's - eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) - are found in abundance in cold water fish such as salmon, trout, mackerel and tuna. The sources of third type of omega-3, alpha-linolenic acid (ALA), are certain vegetable oils (such as flaxseed oil) and leafy greens (such as purslane). However, ALA may not be as effective as EPA and DHA; this is still being researched.
Omega-3's play an important role in a range of vital blood processes, from regulating blood pressure and blood clotting to boosting immunity. They may be useful for preventing or treating m,any diseases and disorders. Fish oil supplements are not necessary for heart disease prevention or treatment if you eat oily fish at least twice a week. However, supplements are recommended for rheumatoid arthritis and other inflammatory conditions.
A recent study involving 120 kids in County Durham found that supplements of omega-3's can help to improve the reading and writing abilities and concentration of children with learning difficulties.