The effects of vitamin D supplementation on proatherogenic inflammatory markers and carotid intima media thickness in subjects with metabolic syndrome: a randomized double-blind placebo-controlled clinical trial

Metabolic syndrome may predispose to cardiovascular diseases. Since, in recent studies, vitamin D is advocated for cardioprotective roles, this study was designed to investigate the effects of vitamin D supplementation on proatherogenic inflammatory markers and common carotid intima media thickness in subjects with metabolic syndrome. This randomized double blind clinical trial was conducted in Tabriz, Iran. Eligible subjects (n = 80) with metabolic syndrome were recruited thorough advertisement and randomized to receive either vitamin D (50,000 IU/week) or matching placebo for 16 weeks. Interlukin-6, high sensitivity C-reactive protein, vascular cell adhesion molecule-1, E-selectin, and common carotid intima media thickness were measured at the beginning and end of the study. The study was registered at (code: IRCT201409033140N14). Sixteen weeks supplementation with vitamin D increased median of serum 25-hydroxy vitamin D [25(OH)D] and mean calcium levels (p < 0.001) in the intervention group. There was also a significant difference in parathyroid hormone level at the end of the study (p < 0.001). Vitamin D treatment reduced IL-6 level after 16 weeks (p = 0.027). Compared to baseline, vascular cell adhesion molecule-1 and E-selectin levels decreased significantly in vitamin D treated subjects; however, there were no significant differences between two groups. No effect of vitamin D supplementation was observed in either common carotid intima media thickness or high sensitivity C-reactive protein concentrations at the end of the study (p > 0.05). Vitamin D supplementation improved some proatherogenic inflammatory markers in subjects with metabolic syndrome. No changes of high sensitivity C-reactive protein and carotid intima media thickness were shown after 16 weeks.