Does Vitamin D actually make a difference, or is it overhyped?

A large meta-analysis in the BMJ and an earlier meta-analysis both found vitamin D supplementation modestly reduces all-cause mortality, though effects are inconsistent across trial populations. Weighing the data: Vitamin D looks an early-stage, lower-priority area for now — the evidence is only moderate (51/100), and its estimated impact (36/100) is on the lower end too.