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 .
Randomized comparison of the effects of the vitamin D3 adequate intake versus 100 mcg (4000 IU) per day on biochemical responses and the wellbeing of patients
Background For adults , vitamin D intake of 100 mcg ( 4000 IU)/day is physiologic and safe . The adequate intake ( AI ) for older adults is 15 mcg ( 600 IU)/day , but there has been no report focusing on use of this dose . Methods We compared effects of these doses on biochemical responses and sense of wellbeing in a blinded , r and omized trial . In Study 1 , 64 out patients ( recruited if summer 2001 25(OH)D < 61 nmol/L ) were given 15 or 100 mcg/day vitamin D in December 2001 . Biochemical responses were followed at subsequent visits that were part of clinical care ; 37 patients completed a wellbeing question naire in December 2001 and February 2002 . Subjects for Study 2 were recruited if their 25(OH)D was < 51 nmol/L in summer 2001 . 66 out patients were given vitamin D ;  51 completed a wellbeing question naire in both December 2002 and February 2003 . Results In Study 1 , basal summer 25-hydroxyvitamin D [ 25(OH)D ] averaged 48 ± 9 ( SD ) nmol/L. Supplementation for more than 6 months produced mean 25(OH)D levels of 79 ± 30 nmol/L for the 15 mcg/day group , and 112 ± 41 nmol/L for the 100 mcg/day group . Both doses lowered plasma parathyroid hormone with no effect on plasma calcium . Between December and February , wellbeing score improved more for the 100-mcg/day group than for the lower-dosed group ( 1-tail Mann-Whitney p = 0.036 ) . In Study 2 , 25(OH)D averaged 39 ± 9 nmol/L , and winter wellbeing scores improved with both doses of vitamin D ( two-tail p < 0.001 ) . Conclusion The highest AI for vitamin D  brought summertime 25(OH)D to > 40 nmol/L , lowered PTH , and its use was associated with improved wellbeing . The 100 mcg/day dose produced greater responses . Since it was ethically necessary to provide a meaningful dose of vitamin D to these insufficient patients , we can not rule out a placebo wellbeing response , particularly for those on the lower dose . This work confirms the safety and efficacy of both 15 and 100 mcg/day vitamin D3 in patients who needed additional vitamin
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 .