Vitamin D supplementation and mortality

In the Lancet Diabetes & Endocrinology, Rachel Neale and colleagues 1 present their findings from D-Health, a population-based, double-blind, placebo-controlled vitamin D3 intervention trial in older Australian adults (n=21 315). It is the largest study to date to assess the effect of vitamin D supplementation on mortality as the primary outcome. No significant reduction in all-cause mortality or from cancer and cardiovascular disease was found. For cancer mortality, hazard ratio point estimates for intention-to-treat and per-protocol analyses were numerically higher in the intervention group, but 95% CIs were wide and crossed 1. Further analyses showed no effect modification according to predicted vitamin D status, indicated by plasma concentration of 25 hydroxy vitamin D (25[OH]D), and BMI explorative analyses excluding the first 2 years of follow-up found a numerically higher hazard ratio for cancer mortality in the vitamin D treated group, but no significant effect on all-cause mortality.