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 vs broad spectrum phototherapy in the treatment of seasonal affective disorder.
Seasonal Affective Disorder ( SAD ) is prevalent when vitamin D stores are typically low . Broad-spectrum light therapy includes wavelengths between 280 - 320 nm which allow the skin to produce vitamin D. This study was design ed to test the hypothesis that vitamin D deficiency might play a role in SAD . A prospect i ve , r and omized controlled trial was conducted in a group of 15 subjects with SAD . Eight subjects received 100,000 I.U. of vitamin D and seven subjects received phototherapy . At the onset of treatment and after 1 month of therapy subjects were administered the Hamilton Depression scale , the SIGH-SAD , and the SAD-8 depression scale . All subjects also had serum levels of 25-hydroxyvitamin D ( 25-OH D ) measured before and 1 week after intervention therapy . All subjects receiving vitamin D improved in all outcome measures . The phototherapy group showed no significant change in depression scale measures . Vitamin D status improved in both groups ( 74 % vitamin D group , p < 0.005 and 36 % phototherapy group , p < 0.01 ) . Improvement in 25-OH D was significantly associated with improvement in depression scale scores ( r2=0.26 ; p=0.05 ) . Vitamin D may be an important treatment for SAD . Further studies will be necessary to confirm these findings
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 .