Are vitamin D3 supplements useful?

As there were high rates of dropouts in the studies and in some trials biased reporting of outcomes, the reviewers suggested further placebo-controlled randomised trials were warranted.

They identified 56 RCTs of vitamin D supplementation versus placebo or no intervention for an average 4.4 years. The trials involved >95,000 mostly healthy participants (77% women), aged 18–107 years in high income countries.

The reviewers assessed trials involving supplemental vitamin D