A new meta-analysis of randomized controlled trials published in PLOS ONE has found that vitamin D supplementation reduces mortality, specifically over the long run, as opposed to the short run.
There have been previous meta-analyses of randomized controlled trials looking at vitamin D supplementation and mortality. The most notable of which was a Cochrane Review in 2011. In their meta-analysis, researchers included 50 randomized controlled trials and found that vitamin D3 supplementation reduced risk of death by 6% compared to placebo.
In this present, newer analysis, researchers from Guangdong Medical College in Zhanjiang, China, wanted to examine the issue a little differently. They wanted to know, what effect does duration of vitamin D treatment have on mortality? If we systematically review all the trials on vitamin D supplementation, might some studies show greater or lesser efficacy than others due to duration of treatment?