Cancer Epidemiology Biomarkers & Prevention, Vol 5, Issue 4 263-270, Copyright © 1996 by American Association for Cancer Research

ARTICLES

Effects of dietary supplementation of alpha-tocopherol on plasma glutathione and DNA repair activities

JJ Hu, GC Roush, M Berwick, N Dubin, S Mahabir, M Chandiramani and R Boorstein
Lombardi Cancer Center, Georgetown University Medical Center, Washington, DC 20007, USA.

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 in peripheral mononuclear leukocytes. Baseline levels of antioxidants and DNA repair activities were assessed twice before alpha-tocopherol intervention: on day 1 (visit 1) and day 3 (visit 2). During the second visit, participants were randomized to receive one of three dosages of alpha-tocopherol, 15, 60, or 200 mg/day for 4 weeks. The same biochemical measurements as at baseline were repeated twice after intervention: on day 17 (visit 3) and day 31 (visit 4). A total of 31 healthy volunteers were eligible for the study, completed all four visits and were included in the final data analysis. At baseline, no appreciable differences of dietary intake of vitamin E and plasma alpha-tocopherol were observed among the three dosage groups. In general, supplementation of alpha-tocopherol for 2-4 weeks resulted in a dose-dependent increase of plasma level of alpha-tocopherol (compared to baseline); significant increases of plasma alpha-tocopherol at visits 3 and 4 were observed in the two higher dosage groups, 60 and 200 mg, but not in the lowest dosage group, 15 mg. At visit 4 (but not visit 3), plasma glutathione 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 protection ratio by supplementation of alpha-tocopherol for 2-4 weeks in the two higher dosage groups, 60 and 200 mg, but not in the lowest dosage group, 15 mg. In general, there were no consistent effects of alpha-tocopherol on DNA repair activities in peripheral mononuclear leukocytes after being adjusted for baseline DNA repair activities. Results from this study demonstrate the interrelationship between alpha-tocopherol and other antioxidants in plasma; total plasma antioxidants can be modulated by short-term dietary supplementation of alpha-tocopherol.

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