Effects of vitamin C supplementation on antioxidants and lipid peroxidation markers in elderly subjects with type 2 diabetes.

The objective of our study was to evaluate the effects of the administration of two dosages of vitamin C (Vit-C) (0.5 and 1g/day, vs. placebo) in elderly patients with type 2 diabetes mellitus on the intracellular levels of Vit-C and glutathione, and on the lipid peroxidation markers and vitamin E (Vit-E) content of low-density lipoprotein (LDL) and on LDL susceptibility to gamma radiolysis-induced peroxidation. Thirty-six patients were randomized into three groups. In patients on 0.5 g Vit-C/day versus the placebo group, a significant increase in cellular reduced glutathione level was observed (0.60+/-0.26 vs. 0.33+/-0.27). In patients on 1 g Vit-C/day versus placebo, a significant increase was also observed in cellular reduced glutathione (0.93+/-0.70 vs. 0.33+/-0.27), in Vit-C (5.66+/-2.00 vs. 2.72+/-1.88) and in vitamin E content of LDL (1.98+/-0.38 vs. 1.48+/-0.40). No change was observed in either group in basal levels of lipid peroxidation markers and in the susceptibility of LDL to peroxidation provoked by gamma-radiolysis. In conclusion, Vit-C has a dose-dependent effect on the cellular contents of antioxidants and on vitamin E content of LDL in elderly patients with type 2 DM. These changes are not sufficient to decrease the LDL susceptibility to peroxidation.