Vitamin D Outcomes and interventions in Toddlers

Dr Jonathon Maguire, St. Michael’s Hospital, University of Toronto


There is consistent evidence that many North American children older than 1 year have vitamin D serum levels lower than the American Academy of Pediatrics and the Canadian Paediatric Society recommend. Data from the 2001-2004 National Health and Nutrition Examination Survey (NHANES) indicated that 65-70% of children had vitamin D levels <75 nmol/L. However, it is not known what health benefits would be realized if children reached these levels. Observational data has demonstrated an association between low wintertime vitamin D levels and increased risk of viral upper respiratory tract infection (URTI), asthma-related hospitalizations and use of anti-inflammatory medication. However, it is not currently known whether vitamin D supplementation mediates UTRI risk and risk of asthma exacerbations in preschoolers. A randomized controlled trial is urgently needed to determine whether wintertime vitamin D supplementation could result in reductions in viral URTI and asthma, two of the most common and costly illness of early childhood.


This study will compare the effect of ‘standard dose’ (400 IU/day) vs. ‘high dose’ (2000 IU/day) orally supplemented vitamin D in achieving reductions in laboratory confirmed URTI and asthma exacerbations during the winter in preschool aged Canadian children. We also aim to assess the effect of ‘high dose’ wintertime vitamin D supplementation on vitamin D serum levels as well as RSV, adenovirus and influenza viruses as causes of URTI. Data from this RCT will be used to perform an economic analysis of the cost vs. the benefit of routine ‘high dose’ wintertime vitamin D supplementation for preschoolers.