The effect of vitamin C supplementation and withdrawal on the mortality and morbidity of regular hemodialysis patients.

The present study was undertaken to evaluate the effects of vitamin C supplementation (VC-S) on the morbidity and mortality of 61 clinically stable outpatients maintained on regular hemodialysis (HD). All patients were given vitamin C (500 mg daily) for 2 years and observed for a further 2 years on no treatment. VC-S significantly increased the plasma levels of ascorbic acid up to 7.8 mg/dl (mean 3.3 +/- 0.4 s.e.m.) which fell after withdrawal to the normal range (mean 1.2 +/- 0.2 mg/dl). Hyperoxalemia was aggravated by VC-S (mean 61.5 +/- 3.3 mumol/l, range 33.3 to 165.5) while plasma oxalate levels in the unsupplemented period decreased to 36.3 +/- 3.3 mumol/l (p less than 0.01). There were no differences in creatinine, hematocrit, blood transfusion requirement, morbidity (including hospitalization) or mortality between the two periods of time in the same patients. In conclusion, we could not find any beneficial effects on morbidity or mortality as a result of using VC-S in regular HD patients. However, secondary hyperoxalemia was aggravated. As a result of these observations it appears that VC-S is harmful and unnecessary in these patients provided they are on an adequate diet.