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| Sunday, 24 February 2002 |
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Features |  |
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Fish oils: good or bad? by Dr. D.P. Atukorale Essential fatty acids are necessary for good health because they provide the catalysts for various metabolic functions e.g. they can activate cell regulators known as prostaglandins. They are called essential because the body cannot manufacture them. There are 2 classes of essential fatty acids (EFAS) the omega-6 and omega-3 fatty acids. Most vegetable oils provide the EFAS but these are not significantly present in meat. Omega -6 fatty acids are found in vegetable seeds and oils produced from them. Good sources include safflower oil, sunflower oil, corn, soya, evening primrose, pumpkin, and wheat germ. Omega-3 fatty acids are found in deep water fish oils. They are found in linseed oil and soya bean oil. So vegetarians don't have to worry if they consume soya products, soya oil and other vegetable oils. Fish oils are more unsaturated than oils obtained from land animals. Small fish such as Salaya, Hurulla, and Kumbalawa have significant quantities of omega-3 fatty acids. Red fish such as 'Balaya, Kelawala (tuna) and Thalapaya, are good sources of omega-3. White fish such as Thora and Paraw are not good sources of omega-3 fatty acids. Contrary to popular opinion, fish is not the only source of omega-3. Flaxseed (linseed) oil actually contains about twice as much omega-3 as found in fish oils. Flatseed is also rich in omega-6 fatty acids. Other good sources of omega-3 are repeseed (Canola) oil and soya oil. The food supplement, spirulina also contain both omega-3 and omega-6 fatty caids. Although fish oils has been touted as the ultimate cure for heart disease, the evidence is by no means as clear - cut as the publicity given by the multinational drug firms. Large doses of fish oil lower the serum triglyceride level in people who have hypertriglyceridaemia (high serum levels of blood fat known as triglycerides). But this condition is rare in Sri Lanka, the commonest causes of hypertriglyceridaemia being excessive alcoholic intake and uncontrolled diabetes. But when fish oils are continued over a longer period of time (six months) the initial triglyceride lowering effect disappears. The theory that taking fish oil helps patients after PTCA (angioplasty) has been disproved. A large study at Harvard Medical School and Beth Israel Hospital has shown that taking fish oils causes narrowing of coronary arteries and causes more heart attacks than people taking olive oil (G.J. Reis et al, Lancet, Vol. 22, 1999, pages 177-181). The theory that fish oil can reduce arthritis has not been proved. Regarding cholesterol, some studies show that large doses of fish oil can reduce cholesterol levels. Other studies show that fish oil can raise blood cholesterol levels especially the LD1 cholesterol (bad cholesterol) level. |
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