Vitamin C improves endothelial function, especially in patients with cardiovascular disease, meta-analysis shows

Summary

This systematic review and meta-analysis was designed to determine the effect of vitamin C supplementation on endothelial function (EF) and investigate whether the effect was influenced by health status, study duration, dose and route of vitamin C administration.

All randomized, controlled trials published in the literature up to May 2013 with adults, vitamin C monotherapy and quantifiable measures of EF using standard methods (e.g., ultrasound, plethysmography and pulse wave analysis) were eligible for inclusion. A total of 44 clinical trials met the inclusion criteria with a moderate degree of heterogeneity.

Pooling of data showed a significant positive effect of vitamin C on EF with a standardized mean difference (SMD) of 0.50 (95% CI: 0.34, 0.66, P<.001). Stratifying the analysis by health outcome revealed significant EF improvements after vitamin C supplementation in patients with atherosclerosis (SMD: 0.84, 95% CI: 0.41, 1.26, P<.001), diabetes (SMD: 0.52, 95% CI: 0.21, 0.82, P<.001) and heart failure (SMD: 0.48, 95% CI: 0.08, 0.88, P<.02).

The effect size appeared to be unaffected by study design, duration, baseline blood level of vitamin C or route of administration of vitamin C. The meta-regression showed a significant positive association between vitamin C dose and EF improvement (β: 0.00011, 95% CI: 0.00001, 0.00021, P<.05). The effect of vitamin C supplementation appeared to be dependent on health status, with stronger effects in those at higher cardiovascular disease risk.

These findings suggest vitamin C may offer clinical value to support optimal endothelial function, especially in patients at higher cardiovascular risk.