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 .
The Effect of 2 Different Single Injections of High Dose of Vitamin D on Improving the Depression in Depressed Patients With Vitamin D Deficiency: A Randomized Clinical Trial
Abstract The correlation between vitamin D deficiency and depression has recently been put forward and result ed in controversial findings . The present study was conducted to find out the effect of 2 single injections of 150,000 and 300,000 IU of vitamin D on improving the depression in depressed patients with vitamin D deficiency . This clinical trial study was carried out during 2011–2012 in Yazd , Islamic Republic of Iran . A total of 120 patients who had a Beck Depression Inventory II score of 17 + and were affected with vitamin D deficiency were r and omly assigned to 3 groups of 40 . They included G300 , G150 , and NTG . G300 and G150 received an intramuscular single dose of 300,000 and 150,000 IU of vitamin D , respectively , and the NTG group received nothing . After 3 months of intervention , the depression state , serum vitamin D , calcium , phosphorus , and parathormone were measured . The median of serum vitamin D after intervention were 60.2 , 54.6 , and 28.2 nmol/L ( P < 0.001 ) for the G300 , G150 , and NTG , respectively . Percentages of vitamin D deficiency after intervention were 18 , 20 , and 91.2 for the groups , respectively . The serum calcium mean showed a statistically significant increase in just the 2 test groups receiving vitamin D. There was only significant difference in mean of Beck Depression Inventory II test score between G300 and NTG ( P = 0.003).The results of the study revealed that first , the correction of vitamin D deficiency improved the depression state , and second , a single injection dose of 300,000 IU of vitamin D was safe and more effective than a 150,000-IU dose
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 .