LDL oxidation plays an important role in atherogenesis. HDL inhibit the atherogenic effect of oxidized LDL. Oxidative modification of HDL impairs protective effects of HDL. The relationship between LDL and HDL oxidation and composition of lipoproteins [polyunsaturated fatty acids (PUFAs), v itamin E] was determined in blood sample of 24 lactoovovegetarians aged 17.6 years. Alternative nutrition causes higher plasma PUFA content, but also higher content of essential antioxidative vitamins as compared with traditional nutrition. All oxidative parameters [lag time, maximal oxidation rate (Vmax), maximal conjugated diene content (CDmax)] were significantly lower in HDL. The vitamin E content in HDL was significantly decreased. The peroxidizability index of PUFAs was significantly higher in HDL (higher content of fatty acids with C20 and C22 and with 3, 4 and 6 double bonds). The lower resistance of HDL against oxidation may be explained by a lower vitamin E content and higher supply of PUFAs with 3–6 double bonds. The results show the importance of LDL and HDL composition in resistance against oxidation and from this aspect the composition of LDL is more fav ourable when compared to HDL.

        Key words: LDL and HDL oxidation, fatty acids.