Vitamin D plays a critical role in the regulation of calcium and phosphorous levels in the blood. Recent studies, also inconsistent, indicate a correlation between vitamin D supplementation and mortality. This study aims to evaluate the association between vitamin D supplementation and mortality.

This is a systematic review and meta-analysis of randomized controlled trials that included data of 75,454 participants from 52 trials in the datasets of Medline, Embase, and the Cochrane Central Register. The trial compared the effects of vitamin D supplementation with placebo on mortality. The primary outcome of the study was all-cause mortality.

Researchers found no significant association between all-cause mortality and vitamin D supplementation. There was no change in the risk of cause-specific mortality, including cardiovascular mortality and cancer mortality. In fact, vitamin D supplementation reduced the risk of cancer death by 16%. In subgroup analysis, vitamin D3 supplementation was associated with a significantly lower risk of mortality than vitamin D2 supplementation. However, there was no significant statistical reduction in the risk of all-cause mortality in both Vitamin D2 and D3 groups. 

The research concluded that vitamin D supplementation is not associated with all-cause mortality when compared to no treatment or placebo. However, vitamin D supplementation was linked to a reduced risk of cancer death.