Effect of phenol-rich extra virgin olive oil on markers of oxidation in healthy volunteers

Objective: We studied whether consumption of phenol-rich extra virgin olive oil affects the susceptibility of low density lipoproteins (LDL) to oxidation and other markers of oxidation in humans. Design: Randomized cross-over intervention trial, stratified according to sex, age and energy intake. Setting: Division of Human Nutrition and Epidemiology, Wageningen University, The Netherlands. Subjects: Forty-six healthy men and women completed the study. Intervention: Subjects consumed two diets supplying 69 g per day of extra virgin olive oil either rich or poor in phenols for 3 weeks each. The mean difference in phenol intake between the treatments was 18 mg per day. Vitamin E intake was low during the whole study. Fasting blood samples were taken twice at the end of each period. Results: Resistance of LDL and high density lipoprotein (HDL) to oxidation was not affected by treatment. The mean lag time of copper-induced formation of conjugated dienes was 1.6 min shorter in LDL and 0.4 min longer in HDL after the high phenol diet. Other markers of antioxidant capacity in plasma were also not affected: mean lipid hydroperoxides were 0.07 μmol/1 higher, mean malondialdehydes were 0.001 μmol/1 higher, mean protein carbonyls were 0.001 nmol/mg protein lower, and the mean ferric reducing ability of plasma (FRAP) was 0.006 mmol/1 higher after the high phenol diet. All 95␌onfidence intervals enclosed zero. Serum cholesterol concentrations were not affected by the treatment. Conclusion: Consumption of 18 mg per day of phenols from extra virgin olive oil for 3 weeks did not affect LDL or HDL oxidation or other markers of antioxidant capacity in fasting plasma samples.