Background: A recent meta-analysis has demonstrated that the regular administration of high-dose vitamin E supplements may be associated with increased mortality. The biological mechanism for this effect is uncertain.
Methods: A ferrous oxidation xylenol assay was used to assess plasma oxidation activity levels in samples from a randomized, placebo-controlled, 6-week trial of daily vitamin E supplementation in adults with asthma (n = 72).
Results and conclusion: A 27% increase in plasma oxidation activity levels was observed in patients receiving vitamin E. We demonstrate a pro-oxidant effect of high-dose vitamin E supplementation that may explain the increase in mortality observed in intervention studies using this nutrient.