Randomized trial of vitamin D supplementation and risk of acute respiratory infection in Mongolia.
OBJECTIVE
Observational studies suggest that serum levels of 25-hydroxyvitamin D (25[OH]D) are inversely associated with acute respiratory infections (ARIs). We hypothesized that vitamin D supplementation of children with vitamin D deficiency would lower the risk of ARIs.


METHODS
By using cluster randomization, classrooms of 744 Mongolian schoolchildren were randomly assigned to different treatments in winter (January-March). This analysis focused on a subset of 247 children who were assigned to daily ingestion of unfortified regular milk (control; n = 104) or milk fortified with 300 IU of vitamin D(3) (n = 143). This comparison was double-blinded. The primary outcome was the number of parent-reported ARIs over the past 3 months.


RESULTS
At baseline, the median serum 25(OH)D level was 7 ng/mL (interquartile range: 5-10 ng/mL). At the end of the trial, follow-up was 99% (n = 244), and the median 25(OH)D levels of children in the control versus vitamin D groups was significantly different (7 vs 19 ng/mL; P < .001). Compared with controls, children receiving vitamin D reported significantly fewer ARIs during the study period (mean: 0.80 vs 0.45; P = .047), with a rate ratio of 0.52 (95% confidence interval: 0.31-0.89). Adjusting for age, gender, and history of wheezing, vitamin D continued to halve the risk of ARI (rate ratio: 0.50 [95% confidence interval: 0.28-0.88]). Similar results were found among children either below or above the median 25(OH)D level at baseline (rate ratio: 0.41 vs 0.57; P(interaction) = .27).


CONCLUSIONS
Vitamin D supplementation significantly reduced the risk of ARIs in winter among Mongolian children with vitamin D deficiency.
Massachusetts General Hospital, Boston, Massachusetts 02114, USA. ccamargo@partners.org
Carlos A
CA
Camargo
Davaasambuu
D
Ganmaa
A Lindsay
AL
Frazier
Franca F
FF
Kirchberg
Jennifer J
JJ
Stuart
Ken
K
Kleinman
Nyamjav
N
Sumberzul
Janet W
JW
Rich-Edwards
D000208:Acute Disease; D000818:Animals; D002648:Child; D019587:Dietary Supplements; D004311:Double-Blind Method; D005527:Food, Fortified; D006801:Humans; D008892:Milk; D008986:Mongolia; D012141:Respiratory Tract Infections / Q000097:blood / Q000517:prevention & control*; D014807:Vitamin D / Q000008:administration & dosage* / Q000031:analogs & derivatives / Q000097:blood; D014808:Vitamin D Deficiency / Q000150:complications / Q000628:therapy*
D014807:Vitamin D; C104450:25-hydroxyvitamin D