Nowadays, many people believed that the replacement of dietary saturated fat with unsaturated fat is able to reduce the risk of cardiovascular related diseases. However, diet high in PUFA could increase lipid peroxidation, potentially contributing to atherosclerosis. (Higdon et.al 2000)
Polyunsaturated fatty acids are natural constituents of animal and vegetable fats. They are made up of a carbon chain with a methyl group at one terminal and an acid group at the other. These fatty acids are said to be polyunsaturated because they contain several double bonds. Polyunsaturated fats are divided into two families: the omega-3 (n-3) fats and the omega-6 (n-3) fats.
N-6 polyunsaturated fatty acids are found in corn, safflower, soybean, and sunflower oil. N-3 fatty acids, particularly eicosa pentaneoic acid (EPA) and docosahexaenoic acid (DHA) have antiatherogenic effect such as lowering serum VLDL level and therefore lower triglyceride, reduction in the release of cytokines from cells involved in fatty plaque formation, and decrease in plasma triglycerides. Fish oils (rich in omega-3 PUFA) can also reduce platelet aggregation, thus decreasing risk for heart attack and stroke. Besides that, PUFA are inherently more susceptible to oxidation due to their high degree of unsaturation. Studies tend to show a positive association between n-6 PUFA and oxidative stress (Reaven, 1993; Bonanome, 1992; Reaven, 1991).
Polyunsaturated fatty acids are important energy source; it is also an essential component of the cell membranes maintaining its fluidity and function. PUFAs are precursors of eicosanoids (Gil, 2002; Hamosh and Salem, 1998) and they are implicated in gene transcription modulation, mRNA stability, and cellular differentiation. (Fernandez et. al., 2005). The PUFAs of the membrane and of the lipoprotein particles are susceptible to free radical attack and degrade easily by forming lipid hydroperoxides, lipid hydroxides, hydrocarbons, and aldehydes as their stable degradation products; these are implicated in many pathologies diseases such as atherosclerosis, aging, and cancer. (Yagi,1987).