Vitamin D intervention in preschoolers with viral-induced asthma (DIVA): a pilot randomised controlled trial

Background: Trials in school-aged children suggest vitamin D supplementation reduces asthma exacerbations. Primary aim: to examine whether vitamin D-3 (100,000 IU) rapidly raises serum 25-hydroxyvitamin D (25OHD) >= 75 nmol/L in asthmatic preschoolers. Methods: In a double-blind, randomised, placebo-controlled trial, preschool-aged children with asthma received 100,000 IU vitamin D-3 (intervention) or placebo (control), followed by 400 IU vitamin D-3 daily for 6 months. Serum 25OHD was measured at baseline, 10 days, 3 and 6 months. Outcomes included the group difference in 25OHD change from baseline at 3 months (Delta 25OHD); the proportion of children with 25OHD >= 75 nmol/L at 3 months; the pattern in serum vitamin D over 6 months; the proportion of children with hypercalciuria at any time point (safety); and group rates for oral corticosteroids. Continuous outcomes were analysed using generalised linear mixed models and group rate ratios of events per child were assessed using a Poisson distribution model. Results: Twenty-two children were randomised (intervention: 11; control: 11) during winter. At 3 months, the group difference in Delta 25OHD (7.2 nmol/L; 95 % CI: -13.7, 28.1) was not significant; yet, 100 % versus 54.5 % (intervention versus control) had serum 25OHD >= 75 nmol/L. There was a significant group difference in Delta 25OHD at 10 days (110. 3 nmol/ L; 95 % CI: 64.0, 156.6). One child in each group had transient hypercalciuria at 10 days. Group oral corticosteroids rates were 0.82 and 1.18/child, intervention versus control (rate ratio = 0.68; 95 % CI: 0.30, 1.62; nonsignificant). Conclusions: Following 100,000 IU vitamin D-3, all children reached serum 25OHD = 75 nmol/ L, compared with half who received placebo. Daily supplementation, sun exposure and insufficient power may explain the absence of a significant 3-month group difference in Delta 25OHD. No clinically important alterations in bone metabolism biomarkers occurred.