Potential problems of ascorbate and iron supplementation: Pro-oxidant effect in vivo?

The comparison was undertaken between the effects of ascorbate versus ascor bate plus iron supplementation on DNA damage. Twenty healthy subjects with initial levels of plasma ascorbate of 67.2 +/- 23.3 mu mol/l were randomly assigned to and cycled through one of three supplementation regimes: placeb o, 260 mg/d ascorbate, 260 mg/d ascorbate plus 14 mg/d iron for 6 weeks sep arated by 8-week washout periods. Supplementation did not cause a rise in t otal oxidative DNA damage measured by GC-MS. However, a significant decreas e occurred in levels of 8-oxo-7,8-dihydroguanine by ascorbate supplementati on and B-hydroxymethyl uracil by both ascorbate? and ascorbate plus iron su pplementation, relative to the pre-supplemental levels but not to the place bo group. In addition, levels of 5-hydroxymethyl hydantoin and B-hydroxy cy tosine increased significantly, only relative to presupplementation, by asc orbate plus iron treatment. No compelling evidence for a pro-oxidant effect of ascorbate supplementation, in the presence or absence of iron, on DNA b ase damage was observed. (C) 2000 Academic Press.