Effect of vitamin C on endothelial function in health and disease: A systematic review and meta-analysis of randomised controlled trials

Abstract Background Observational studies indicate that higher vitamin C intake is associated with reduced risk for cardiovascular diseases. However, randomised controlled trials (RCT) examining the effect of vitamin C on endothelial function (EF) have reported inconsistent results. The aims of this systematic review and meta-analysis were to determine the effect of vitamin C supplementation on EF and to investigate whether the effect was influenced by health status, study duration, dose and route of vitamin C administration. Methods We searched the Medline, Embase, Cochrane Library, and Scopus databases from inception to May 2013 for studies that met the following criteria: 1) RCT with adult participants, 2) vitamin C administered alone, 3) studies that quantified EF using commonly applied methods including ultrasound, plethysmography and pulse wave analysis. Results Pooling the data from 44 clinical trials showed a significant positive effect of vitamin C on EF (SMD: 0.50, 95% CI: 0.34, 0.66, P