The evidence shows that vitamin D supplementation provides some benefit in fracture prevention ( likely ∼10–15 % relative reduction ) , particularly at a dose ≥800 IU and with calcium ; a likely benefit in the rate of falls , though it is less clear whether the number of fallers changes ; and a possible small ( ∼5 % ) relative reduction in mortality .
Evidence does not support the use of vitamin D supplementation for the prevention of cancer , respiratory infections or rheumatoid arthritis .
Similarly , evidence does not support vitamin D supplementation for the treatment of multiple sclerosis and rheumatoid arthritis or for improving depression/mental well-being .
Regular testing of 25-hydroxyvitamin D is generally not required , and mega-doses ( ≥300,000 IU ) appear to increase harms .
Over the past decade , a large body of observational evidence has suggested an association between  lower vitamin D status ( 25-hydroxyvitamin D ) and multiple acute and chronic disorders , including cancer , multiple sclerosis , depression and respiratory tract infections .
This evidence has fostered the hypothesis that increasing vitamin D intake may treat and prevent such disorders .
Our objective was to perform a critical analysis of the highest-level evidence for ten common beliefs regarding vitamin D for the prevention of falls , fractures and respiratory tract infections , the reduction of cancer incidence/mortality and overall mortality , and the prevention or treatment of depression/mental well-being , rheumatoid arthritis and multiple sclerosis , as well as maximum dosing and regular testing .
Effect on the incidence of pneumonia of vitamin D supplementation by quarterly bolus dose to infants in Kabul: a randomised controlled superiority trial
Summary Background Vitamin D has a role in regulating immune function , and its deficiency is a suggested risk factor for childhood pneumonia . Our aim was to assess whether oral supplementation of vitamin D3 ( cholecalciferol ) will reduce the incidence and severity of pneumonia in a high-risk infant population . Methods We did a r and omised placebo-controlled trial to compare oral 100 000 IU ( 2·5 mg ) vitamin D3 with placebo given to children aged 1–11 months in Kabul , Afghanistan . R and omisation was by use of a computer-generated list . Vitamin D or placebo was given by fieldworkers once every 3 months for 18 months . Children presenting at the study hospital with signs of pneumonia had their diagnosis confirmed radiographically . Our primary outcome was the first or only episode of radiologically confirmed pneumonia . Our analysis was by intention to treat . This study is registered with Clinical Trials.gov , number NCT00548379 . Findings 1524 children were assigned to receive vitamin D3 and 1522 placebo .  There was no significant difference between the incidence of first or only pneumonia between the vitamin D ( 0·145 per child per year , 95 % CI 0·129–0·164 ) and the placebo group ( 0.137 , 0·121–0·155 ) ; the incidence rate ratio was 1·06 ( 95 % CI 0·89–1·27 ) . From 652 children during five separate periods of testing serum calcifediol , only one child in each of two testing periods had results greater than 375 nmol/L in the intervention group — a toxic level . Interpretations Quarterly bolus doses of oral vitamin D3 supplementation to infants are not an effective intervention to reduce the incidence of pneumonia in infants in this setting . Funding Wellcome Trust and British Council
The evidence shows that vitamin D supplementation provides some benefit in fracture prevention ( likely ∼10–15 % relative reduction ) , particularly at a dose ≥800 IU and with calcium ; a likely benefit in the rate of falls , though it is less clear whether the number of fallers changes ; and a possible small ( ∼5 % ) relative reduction in mortality .
Evidence does not support the use of vitamin D supplementation for the prevention of cancer , respiratory infections or rheumatoid arthritis .
Similarly , evidence does not support vitamin D supplementation for the treatment of multiple sclerosis and rheumatoid arthritis or for improving depression/mental well-being .
Regular testing of 25-hydroxyvitamin D is generally not required , and mega-doses ( ≥300,000 IU ) appear to increase harms .
Over the past decade , a large body of observational evidence has suggested an association between  lower vitamin D status ( 25-hydroxyvitamin D ) and multiple acute and chronic disorders , including cancer , multiple sclerosis , depression and respiratory tract infections .
This evidence has fostered the hypothesis that increasing vitamin D intake may treat and prevent such disorders .
Our objective was to perform a critical analysis of the highest-level evidence for ten common beliefs regarding vitamin D for the prevention of falls , fractures and respiratory tract infections , the reduction of cancer incidence/mortality and overall mortality , and the prevention or treatment of depression/mental well-being , rheumatoid arthritis and multiple sclerosis , as well as maximum dosing and regular testing .