"Vitamin C supplementation improved endothelial function. The effect of vitamin C supplementation appeared to be dependent on health status, with stronger effects in those at higher cardiovascular disease risk."
Effect of vitamin C on endothelial function in health and disease: A systematic review and meta-analysis of randomised controlled trials
http://www.atherosclerosis-journal.com/article/S0021-9150(14)00203-2/fulltext