Open Access Open Badges Study protocol

DO IT Trial: vitamin D Outcomes and Interventions in Toddlers a TARGet Kids! randomized controlled trial

Jonathon L Maguire12347*, Catherine S Birken347, Mark B Loeb8, Muhammad Mamdani15, Kevin Thorpe16, Jeffrey S Hoch10579, Tony Mazzulli1112, Cornelia M Borkhoff37, Colin Macarthur34, Patricia C Parkin347 and on behalf of the TARGet Kids! Collaboration

Author Affiliations

1 The Applied Health Research Centre of the Li Ka Shing Knowledge Institute of St. Michael’s Hospital, University of Toronto, Toronto, Ontario, Canada

2 Department of Pediatrics, St. Michael’s Hospital, 30 Bond Street, 15-014 Cardinal Carter, Toronto, Ontario, M5B 1 W8, Canada

3 Pediatric Outcomes Research Team (PORT), Division of Pediatric Medicine, Department of Pediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada

4 Department of Pediatrics, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada

5 Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada

6 Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada

7 Institute for Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada

8 Department of Pathology and Molecular Medicine and Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada

9 Pharmacoeconomics Research Unit, Cancer Care Ontario, Toronto, Ontario, Canada

10 Centre for Excellence in Economic Analysis Research, Li Ka Shing Knowledge Institute of St. Michael’s Hospital, University of Toronto, Toronto, Ontario, Canada

11 Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada

12 Department of Microbiology, Mount Sinai Hospital and University Health Network, Toronto, Ontario, Canada

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BMC Pediatrics 2014, 14:37  doi:10.1186/1471-2431-14-37

Published: 8 February 2014



Vitamin D levels are alarmingly low (<75 nmol/L) in 65-70% of North American children older than 1 year. An increased risk of viral upper respiratory tract infections (URTI), asthma-related hospitalizations and use of anti-inflammatory medication have all been linked with low vitamin D. No study has determined whether wintertime vitamin D supplementation can reduce the risk of URTI and asthma exacerbations, two of the most common and costly illnesses of early childhood. The objectives of this study are: 1) to compare the effect of ‘high dose’ (2000 IU/day) vs. ‘standard dose’ (400 IU/day) vitamin D supplementation in achieving reductions in laboratory confirmed URTI and asthma exacerbations during the winter in preschool-aged Canadian children; and 2) to assess the effect of ‘high dose’ vitamin D supplementation on vitamin D serum levels and specific viruses that cause URTI.


This study is a pragmatic randomized controlled trial. Over 4 successive winters we will recruit 750 healthy children 1–5 years of age. Participating physicians are part of a primary healthcare research network called TARGet Kids!. Children will be randomized to the ‘standard dose’ or ‘high dose’ oral supplemental vitamin D for a minimum of 4 months (200 children per group). Parents will obtain a nasal swab from their child with each URTI, report the number of asthma exacerbations and complete symptom checklists. Unscheduled physician visits for URTIs and asthma exacerbations will be recorded. By May, a blood sample will be drawn to determine vitamin D serum levels. The primary analysis will be a comparison of URTI rate between study groups using a Poisson regression model. Secondary analyses will compare vitamin D serum levels, asthma exacerbations and the frequency of specific viral agents between groups.


Identifying whether vitamin D supplementation of preschoolers can reduce wintertime viral URTIs and asthma exacerbations and what dose is optimal may reduce population wide morbidity and associated health care and societal costs. This information will assist in determining practice and health policy recommendations related to vitamin D supplementation in healthy Canadian preschoolers.

Vitamin D deficiency; Vitamin D supplementation; Infant; Toddler