Vitamin C and Endothelial Dysfunction: What Is New?

Abstract

To the Editor: Several papers recently published in Circulation ,1 2 3 and 1 in the Journal of Clinical Investigation ,4 report that vitamin C is able to improve endothelial dysfunction. In each of these studies, the hypothesis is formulated that vitamin C may cause such an effect through its antioxidant activity, protecting NO from inactivation by superoxide anion. Regarding all these studies, 3 questions should be taken into consideration: 1. The reported experiments do not constitute a strong support for the attribution of the effects of vitamin C to its antioxidant action. A demonstration that different antioxidants reproduce the same effect would have been useful. 2. Clinical trials based on the administration of vitamin C should be suggested with caution. Apart from the possibly increased risk of the formation of urinary oxalate stones during therapy with megadoses of ascorbic acid,5 vitamin C has been shown to increase the production of advanced glycation end products in diabetic patients.6 Moreover, several studies have demonstrated that vitamin C contributes only about 10% to the total antioxidant capacity of plasma.7 8 3. The bibliographies of all the above-mentioned studies do not adequately …