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 .
Single data extraction generated more errors than double data extraction in systematic reviews.
BACKGROUND AND OBJECTIVE To conduct a pilot study to compare the frequency of errors that accompany single vs. double data extraction , compare the estimate of treatment effect derived from these methods , and compare the time requirements for these methods . METHODS Review ers were r and omized to the role of data extractor or data verifier , and were blind to the study hypothesis . The frequency of errors associated with each method of data extraction was compared using the McNemar test . The data set for each method was used to calculate an efficacy estimate by each method , using st and ard meta-analytic techniques . The time requirement for each method was compared using a paired t-test . RESULTS Single data extraction result ed in more errors than double data extraction ( relative difference : 21.7 % , P = .019 ) . There was no substantial difference between methods in effect estimates for most outcomes . The average time spent for single data extraction  was less than the average time for double data extraction ( relative difference : 36.1 % , P = .003 ) . CONCLUSION In the case that single data extraction is used in systematic review s , review ers and readers need to be mindful of the possibility for more errors and the potential impact these errors may have on effect estimates
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 .