OMEGA-3-FATTY-ACIDS - NUTRITIONAL ASPECTS

Omega-3 fatty acids contain a double bond in the third position from t he methyl group. The very long-chain (20 or 22 carbon atoms) omega-3 f atty acids are mostly found in fatty fish and fish oils. The omega-3 f atty acids are essential and may act as precursors for eicosanoids, al tering membrane fluidity or binding to transcription factors. Dietary intake of omega-3 fatty acids reduces plasma concentration of triglyce rides, probably by decreasing hepatic secretion of very low density li poprotein (VLDL) and by increasing catabolism of chylomicrons. In addi tion, lipid peroxidation of omega-3 fatty acids may take place, with g ood and bad consequences. As the number of double bonds is high, the o mega-3 fatty acids may easily react with oxygen radicals. We performed studies where 5 g/day of very long-chain omega-3 fatty acids was give n as a supplement for four months along with vitamin E, whereas contro l groups received similar amounts of other oils. The unsaturation inde x was higher in fatty acids of LDL from individuals exposed to omega-3 fatty acids, and the amounts of cholesteryl esters and total lipids w ere lower compared with control LDL, whereas similar electrophoretic m obility and apolipoprotein B structure were observed. There was a decr ease in the melting temperature of cholesteryl esters in omega-3 fatty acid-enriched LDL, but no change in the susceptibility of LDL to Cu2 catalyzed lipid peroxidation, as measured by changes in amounts of li pid peroxides or in the uptake of LDL im macrophages. These data have been verified by others, whereas three publications reported that fish oil supplementation was associated with increased sings of lipid pero xidation. Recently it has been shown that peroxidation of LDL by white blood cells might be reduced by increased cellular content of omega-3 fatty acids. In conclusion, the susceptibility of LDL to in vitro per oxidation may be increased with dietary intake of omega-3 fatty acids, unless adequate amounts of antioxidants are provided. Reduced intake of foods with high content of saturated fatty acids (fatty milk produc ts, meat, hard margarines) and increased intake of foods providing hig h amounts of omega-3 fatty acids (fatty fish) and antioxidants (fruits , vegetables) are recommended. These precautions will most likely prom ote reduced incidence of coronary artery disease, inflammatory disease s and certain forms of cancer.