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 .
Effects of vitamin D supplementation on symptoms of depression in overweight and obese subjects: randomized double blind trial.
OBJECTIVES The objective of the present study was to examine the cross-sectional relation between serum 25-hydroxyvitamin D [ 25-(OH ) D ] levels and  depression in overweight and obese subjects and to assess the effect of vitamin D supplementation on depressive symptoms . DESIGN Cross-sectional study and r and omized double blind controlled trial of 20,000 or 40,000 IU vitamin D per week versus placebo for 1 year . SETTING A total of 441 subjects ( body mass index 28 - 47 kg m(-2 ) , 159 men and 282 women , aged 21 - 70 years ) recruited by advertisements or from the out-patient clinic at the University Hospital of North Norway . MAIN OUTCOME MEASURES Beck Depression Inventory ( BDI ) score with subscales 1 - 13 and 14 - 21 . RESULTS Subjects with serum 25(OH)D levels < 40 nmol L(-1 ) scored significantly higher ( more depressive traits ) than those with serum 25(OH)D levels > or = 40 nmol L(-1 ) on the BDI total [ 6.0 ( 0 - 23 ) versus 4.5 ( 0 - 28 ) ( median and range ) ] and the BDI subscale 1 - 13 [ 2.0 ( 0 - 15 ) versus 1.0 ( 0 - 29.5 ) ] ( P < 0.05 ) . In the two groups given vitamin D , but not in the placebo group , there was a significant improvement in BDI scores after 1 year . There was a significant decrease in serum parathyroid hormone in the two vitamin D groups without a concomitant increase in serum calcium . CONCLUSIONS It appears to be a relation between serum levels of 25(OH)D and symptoms of depression . Supplementation with high doses of vitamin D seems to ameliorate these symptoms indicating a possible causal relationship
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 .