Serum lipid resistance to oxidation and antioxidative status in vegetarians

In vegetarians a higher consumption of fruits and vegetables is associated with a higher plasma levels of natural antioxidants, which can protect plasma lipoproteins against oxidation. We investigated the relationship between individual constituents of plasma antioxidative status and the resistance of serum lipids to oxidation in 58 lactoovovegetarians (24 male, 34 female). Because of the observed differences in antioxidative status as well as in some parameters of serum lipid resistance in both sexes, the results between vegetarian men and women were compared. No significant differences were found in plasma total cholesterol, HDL cholesterol, LDL cholesterol, and triacylglycerols between vegetarian men and women. The changes in the resistance of serum lipids to oxidation as measured by the duration of the lag time of conjugated diene formation and maximal rate of oxidation have shown significantly prolonged lag time in vegetarian men when compared with women (p = 0.03). Vegetarian men had also significantly higher plasma uric acid concentrations (p = 0.00) and total antioxidative status (p = 0.05) than vegetarian women. No significant differences in plasma a-tocopherol, retinol, beta -carotene and ascorbic acid levels between both sexes were found. In vegetarian men lag time was positively related to total antioxidative status (r = 0.53; p = 0.01) and vitamin C level (r = 0.48; p = 0.02) while no significant correlations with rr-tocopherol and beta -carotene were observed. In vegetarian women a positive correlation between lag time and vitamin C levels (r = 0.49; p = 0.00) and negative correlations with vitamin E levels (r = -0.42; p = 0.01) and HDL cholesterol levels (r = -0.53; p = 0.00) were significant. Unexpectedly, no correlation was found between lag time and plasma uric acid concentrations between groups (r = 0.20 and r = 0.06, men and women group, respectively, p > 0.05 in both) and paradoxically also between total antioxidative status and uric acid concentrations. We conclude that the resistance of serum lipids to in vitro oxidation was different in vegetarian men and women and it significantly depended on total plasma antioxidative status particularly in vegetarian men.