Recent meta-analyses reinforce the finding that 10 - 20 μg per day of vitamin D can reduce all-cause mortality and cancer mortality in middle-aged and older people .
Although vitamin D doses were greater than those assessed in the past , we found no new evidence that supplementation could have an effect on most non-skeletal conditions , including cardiovascular disease , adiposity , glucose metabolism , mood disorders , muscular function , tuberculosis , and colorectal adenomas , or on maternal and perinatal conditions .
The compilation of results from 83 trials showed that vitamin D supplementation had no significant effect on biomarkers of systemic inflammation .
The main new finding highlighted by this systematic review is that vitamin D supplementation might help to prevent common upper respiratory tract infections and asthma exacerbations .
There remains little evidence to suggest that vitamin D supplementation has an effect on most conditions , including chronic inflammation , despite use of increased doses of vitamin D , strengthening the hypothesis that low vitamin D status is a consequence of ill health , rather than its cause .
We further hypothesise that vitamin D supplementation could exert immunomodulatory effects that strengthen resistance to acute infections , which would reduce the risk of death in debilitated individuals .
Vitamin D 20,000 IU per Week for Five Years Does Not Prevent Progression From Prediabetes to Diabetes.
CONTEXT Vitamin D deficiency is associated with insulin resistance and risk of future diabetes . OBJECTIVE The objective of the study was to test whether supplementation with vitamin D to subjects with prediabetes will prevent progression to type 2 diabetes mellitus ( T2DM ) . DESIGN This was a r and omized controlled trial performed in 2008 through 2015 . SETTING The study was conducted at the clinical research unit at a teaching hospital . PATIENTS Five hundred eleven subjects ( mean age 62 y , 314 males ) with prediabetes diagnosed with an oral glucose tolerance test as part of the Tromsø Study 2007–2008 were included . A total of 256 were r and omized to vitamin D and 255 to placebo .  Twenty-nine subjects in the vitamin D and 24 in the placebo group withdrew because of adverse events . INTERVENTIONS Interventions included vitamin D ( cholecalciferol ) 20 000 IU/wk vs placebo for 5 years . Annual oral glucose tolerance tests were performed . MAIN OUTCOME MEASURE Progression to T2DM was the main outcome measure . Secondary outcomes were change in glucose levels , insulin resistance , serum lipids , and blood pressure . RESULTS The mean baseline serum 25-hydroxyvitamin D level was 60 nmol/L ( 24 ng/mL ) . One hundred three in the vitamin D and 112 in the placebo group developed T2DM ( hazard risk 0.90 ; 95 % confidence interval 0.69–1.18 , Cox regression , P = .45 , intention to treat analysis ) . No consistent significant effects on the other outcomes were seen . Subgroup analyses in subjects with low baseline 25-hydroxyvitamin D yielded similar results . No serious side effects related to the intervention were recorded . CONCLUSIONS In subjects without vitamin D deficiency , vitamin D supplementation is unlikely to prevent progression from prediabetes to diabetes . Very large studies with inclusion of vitamin D-deficient subjects will probably be needed to show such a putative effect . This study tested if supplementation with  vitamin D to subjects with prediabetes will prevent progression to type 2 diabetes ( T2DM )
Recent meta-analyses reinforce the finding that 10 - 20 μg per day of vitamin D can reduce all-cause mortality and cancer mortality in middle-aged and older people .
Although vitamin D doses were greater than those assessed in the past , we found no new evidence that supplementation could have an effect on most non-skeletal conditions , including cardiovascular disease , adiposity , glucose metabolism , mood disorders , muscular function , tuberculosis , and colorectal adenomas , or on maternal and perinatal conditions .
The compilation of results from 83 trials showed that vitamin D supplementation had no significant effect on biomarkers of systemic inflammation .
The main new finding highlighted by this systematic review is that vitamin D supplementation might help to prevent common upper respiratory tract infections and asthma exacerbations .
There remains little evidence to suggest that vitamin D supplementation has an effect on most conditions , including chronic inflammation , despite use of increased doses of vitamin D , strengthening the hypothesis that low vitamin D status is a consequence of ill health , rather than its cause .
We further hypothesise that vitamin D supplementation could exert immunomodulatory effects that strengthen resistance to acute infections , which would reduce the risk of death in debilitated individuals .