A Meta‐Analysis on the Effect of Vitamin D Supplementation on Endothelial Function in Adults

Vitamin D is recognized as a key regulator of endothelial function, and its deficiency has been implicated in the development of endothelial dysfunction, a critical contributor to cardiovascular diseases. Many randomized controlled trials (RCTs) have revealed the benefits of vitamin D on endothelial function, but the results are inconclusive. This meta‐analysis of RCTs aimed to assess the effects of vitamin D on endothelial function. A systematic review of PubMed, Embase, Scopus, Web of Science, and Cochrane Library was conducted and covered all records from database inception through May 2025. Data were pooled using a random‐effects model to calculate standardized mean differences (SMDs) and 95% confidence intervals (CIs). Thirty‐one RCTs comprising 35 intervention arms with 3252 patients were included. Findings indicated no significant changes in terms of endothelial function following vitamin D administration including measures such as flow‐mediated dilation (FMD) (SMD = 0.36; 95% CI: −0.11, 0.83, p = 0.131), augmentation index (AIx) level (SMD = −0.12; 95% CI: −0.33, 0.10, p = 0.293), pulse wave velocity (PWV) (SMD = −0.09; 95% CI: −0.25, 0.07, p = 0.258), and intercellular adhesion molecule‐1 (ICAM‐1) (SMD = −0.78; 95% CI: −1.79, 0.22, p = 0.125). However, subgroup analysis revealed that patients with chronic kidney disease showed a significant improvement in PWV following vitamin D supplementation. The present meta‐analysis demonstrated no significant impact of vitamin D treatment on endothelial function. However, heterogeneity in study populations, baseline vitamin D status, dosage, and intervention duration may have influenced the outcomes. Further well‐designed trials are warranted to illustrate its effects on vascular health in large scale.