EFFECTS OF DIETARY SUPPLEMENTATION OF ALPHA-TOCOPHEROL ON PLASMA GLUTATHIONE AND DNA-REPAIR ACTIVITIES

In a randomized double-blind trial of alpha-tocopherol (vitamin E), we investigated the effects of alpha-tocopherol supplementation on lipid - and water-soluble antioxidants in plasma and DNA repair activities i n peripheral mononuclear leukocytes, Baseline levels of antioxidants a nd DNA repair activities were assessed twice before alpha-tocopherol i ntervention: on day 1 (visit 1) and day 3 (visit 2). During the second visit, participants were randomized to receive one of three dosages o f alpha-tocopherol, 15, 60; or 200 mg/day for 4 weeks, The same bioche mical measurements as at baseline were repeated twice after interventi on: on day 17 (visit 3) and day 31 (visit 4), A total of 31 healthy vo lunteers were eligible for the study, completed all four visits and we re included in the final data analysis, At baseline, no appreciable di fferences of dietary intake of vitamin E and plasma alpha-tocopherol w ere observed among the three dosage groups, In general, supplementatio n of alpha-tocopherol for 2-4 weeks resulted in a dose-dependent incre ase of plasma level of alpha-tocopherol (compared to baseline); signif icant increases of plasma alpha-tocopherol at visits 3 and 4 were obse rved in the two higher dosage groups, 60 and 200 mg, but not in the lo west dosage group, 15 mg, At visit 4 (but not visit 3), plasma glutath ione levels were significantly elevated (compared to baseline) in the two higher dosage groups, 60 and 200 mg, but not in the lowest dosage group, 15 mg, In addition, there was an increase in the lipid protecti on ratio by supplementation of cy-tocopherol for 2-4 weeks in the two higher dosage groups, 60 and 200 mg, but not in the lowest dosage grou p, 15 mg, in general, there were no consistent effects of alpha-tocoph erol on DNA repair activities in peripheral mononuclear leukocytes aft er being adjusted for baseline DNA repair activities, Results from thi s study demonstrate the interrelationship between alpha-tocopherol and other antioxidants in plasma; total plasma antioxidants can be modula ted by short-term dietary supplementation of alpha-tocopherol.