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 .
Vitamin D supplementation and depression in the women's health initiative calcium and vitamin D trial.
While observational studies have suggested that vitamin D deficiency increases risk of depression , few clinical trials have tested whether vitamin D supplementation affects the occurrence of depression symptoms . The authors evaluated the impact of daily supplementation with 400 IU of vitamin D(3 ) combined with 1,000 mg of elemental calcium on measures of depression in a r and omized , double-blinded US trial comprising 36,282 postmenopausal women . The Burnam scale and current use of antidepressant medication were used to assess depressive symptoms at r and omization ( 1995 - 2000 ) . Two years later , women again reported on their antidepressant use , and 2,263 completed a second Burnam scale . After 2 years , women r and omized to receive vitamin D and calcium had an odds ratio for experiencing depressive symptoms ( Burnam score ≥0.06 ) of 1.16 ( 95 % confidence interval : 0.86 , 1.56 ) compared with women in the placebo group . Supplementation was not associated with antidepressant use ( odds ratio = 1.01 , 95 % confidence interval : 0.92 , 1.12 ) or continuous depressive symptom score . Results stratified by  baseline vitamin D and calcium intake , solar irradiance , and other factors were similar . The findings do not support a relation between supplementation with 400 IU/day of vitamin D(3 ) along  with calcium and depression in older women . Additional trials testing higher doses of vitamin D are needed to determine whether this nutrient may help prevent or treat depression
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 .