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 .
Effect of Prenatal Supplementation With Vitamin D on Asthma or Recurrent Wheezing in Offspring by Age 3 Years: The VDAART Randomized Clinical Trial.
IMPORTANCE Asthma and wheezing begin early in life , and prenatal vitamin D deficiency has been variably associated with these disorders in offspring . OBJECTIVE To determine whether prenatal vitamin D ( cholecalciferol ) supplementation can prevent  asthma or recurrent wheeze in early childhood . DESIGN , SETTING , AND PARTICIPANTS The Vitamin D Antenatal Asthma Reduction Trial was a r and omized , double-blind , placebo-controlled trial conducted in 3 centers across the United States . Enrollment began in October 2009 and completed follow-up in January 2015 . Eight hundred eighty-one pregnant women between the ages of 18 and 39 years at high risk of having children with asthma were r and omized at 10 to 18 weeks ' gestation . Five participants were deemed ineligible shortly after r and omization and were discontinued . INTERVENTIONS Four hundred forty women were r and omized to receive daily 4000 IU vitamin D plus a prenatal vitamin containing 400 IU vitamin D , and 436 women were r and omized to receive a placebo plus a prenatal vitamin containing 400 IU vitamin D. MAIN OUTCOMES AND MEASURES Co primary outcomes of ( 1 ) parental report of physician-diagnosed asthma or recurrent wheezing through 3 years of age and ( 2 ) third trimester maternal 25-hydroxyvitamin D levels . RESULTS Eight hundred ten infants were born in the study , and 806 were included in the analyses for the 3-year outcomes . Two hundred eighteen children developed asthma or recurrent wheeze : 98 of 405 ( 24.3 % ; 95 % CI , 18.7%-28.5 % ) in the 4400-IU group vs 120 of 401 ( 30.4 % , 95 % CI , 25.7%-73.1 % ) in the 400-IU group ( hazard ratio , 0.8 ; 95 % CI , 0.6 - 1.0 ; P = .051 ) . Of the women in the 4400-IU group whose blood levels were checked , 289 ( 74.9 % ) had 25-hydroxyvitamin D levels of 30 ng/mL or higher by the third trimester of pregnancy compared with 133 of 391 ( 34.0 % ) in the 400-IU group ( difference , 40.9 % ; 95 % CI , 34.2%-47.5 % , P < .001 ) . CONCLUSIONS AND RELEVANCE In pregnant women at risk of having a child with asthma , supplementation with 4400 IU/d of vitamin D compared with 400 IU/d significantly increased vitamin D levels in the women . The incidence of asthma and recurrent wheezing in their children at age 3 years was lower by 6.1 % , but this did not meet statistical significance ; however , the study may have been underpowered . Longer follow-up of the children is ongoing to determine whether the difference is clinical ly important . TRIAL REGISTRATION clinical trials.gov Identifier : NCT00920621
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 .