Bioavailability of antioxidant vitamins. Relation between the modality of intake and plasma markers of oxidative stress

Keywords Antioxidant vitamins Plasma oxidative stress Modality of intakeIntroductionExperimental and epidemiological data suggest that anti-oxidant vitamin supplementation may preventcardiovascular events [1]. Clinical trials have generallyfailed to confirm benefits [2, 3], possibly due to themodality of intake, in relation to food.The aim of the studyThe aim of the study was to assess the relation between themodality of vitamin intake with plasma markers of oxida-tive stress.Patients and methodsForty-four cardiovascular event-free obese men withoutothers CHD risk factors, without symptoms of inflamma-tory disease and the control group of normoweight healthysubjects (n = 18) were included in the study. Combinedsupplementary vitamin E and vitamin C (2 · 100 and2 · 200 mg daily, respectively) was administered to obesesubjects and the control group on an empty stomach (mode‘‘Fasting’’) or during dinner (mode ‘‘Meal’’), for 14 days,after 14 days of washing period in cross-over study. Allsubjects were evaluated using lipoprotein profile, anthro-pometric parameters, body composition (BMI, WHR, % ofadipose tissue) and insulin resistance (HOMA-IR).Parameters of oxidative stress: TBARS, total plasma lipidhydroperoxides (LOOH), LDL oxidative susceptibility, andantioxidant potency parameters: ferric reducing/antioxidantpower test (FRAP), thiol/albumin ratio, vitamin E, C weremeasured. Redox compensation index (RCI) was calcu-lated from formula: RCI = [FRAP/plasma LOOH/cholesterol]/100.ResultsBiomarkers of oxidative damage were higher, parametersof antioxidant defense were lower in obese subjectscompared to control group (Figs. 1, 2). Plasma vitaminlevel increased after supplementation similarly in bothgroups. Vitamin E and C absorption was increased byfood intake (Fig. 3). Plasma antioxidant potency wasincreased and oxidative stress parameters were markedlydiminished by antioxidant supplementation and foodintake (Fig. 4).ConclusionFood intake increases the bioavailability of antioxidantvitamins and improves their free-radical-scavengingactivity.