Effects of dietary fatty acids on the composition and oxidizability of low-density lipoprotein

Objective: The objective of this study was to compare the effects of dietary monounsaturated fatty acids (MUFA), n-6 and n-3 polyunsaturated fatty acids (PUFA) on LDL composition and oxidizability. Design, setting and subjects: Sixty-nine healthy young volunteers, students at a nearby college, were included. Six subjects withdrew because of intercurrent illness and five withdrew because they were unable to comply with the dietary regimen. Interventions: The participants received a 2-week wash-in diet rich in saturated fatty acids (SFA) followed by diets rich in refined olive oil, rapeseed oil or sunflower oil for 4 weeks. Intakes of vitamin E and other antioxidants did not differ significantly between the diets. Results: At the end of the study, LDL oxidizability was lowest in the olive oil group (lag time: 72.6 min), intermediate in the rapeseed oil group (68.2 min) and highest in the sunflower oil group (60.4 min, P < 0.05 for comparison of all three groups). Despite wide variations in SFA intake, the SFA content of LDL was not statistically different between the four diets (25.8 - 28.5% of LDL fatty acids). By contrast, the PUFA (43.5% - 60.5% of LDL fatty acids) and MUFA content of LDL (13.7 - 29.1% of LDL fatty acids) showed a wider variability dependent on diet. Conclusions: Enrichment of LDL with MUFA reduces LDL susceptibility to oxidation. As seen on the rapeseed oil diet this effect is independent of a displacement of higher unsaturated fatty acids from LDL. Evidence from this diet also suggests that highly unsaturated n-3 fatty acids in moderate amounts do not increase LDL oxidizability when provided in the context of a diet rich in MUFA. Sponsorship: This work was supported by the Central Marketing Agency of the German Agricultural Industry (CMA), the German Union for the Promotion of Oil- and Protein Plants (UFOP), the Austrian Science Foundation, project F00709 (to P.M.A.) and the Brokelmann Olmuhle Company, Hamm, Germany.