HOLD IT: Health Outcomes from Low Vitamin D in Toddlers
Dr. Jonathon Maguire, St. Michael’s Hospital, University of Toronto




There is a growing body of evidence that low vitamin D levels in adulthood are associated with a wide variety of adverse health outcomes. A recent meta-analysis of 18 adult randomized controlled trials found a 7% reduction in all cause mortality in adults randomized to vitamin D containing interventions. Emerging pediatric evidence from cross-sectional or retrospective studies suggests that low vitamin D levels early in life may be related to common child health outcomes often seen by primary care physicians.

We have developed a cohort of over 2000 children between 1 and 5 years of age with detailed clinical, anthropometric and laboratory data using a novel primary care practice based research network called TARGet Kids! . Using well established prospective longitudinal cohort study methodology this will be the first large, prospective study to assess the relationship of vitamin D status and the subsequent development of common adverse child health outcomes including fractures, asthma, respiratory infections, obesity and hypertension.



Objectives and Study Procedure


The primary objective is to determine whether low vitamin D level (25-hydroxyvitamin D < 75 nmol/L as defined by the Canadian Paediatric Society) in children 1-5 years of age is associated with the subsequent development of fractures, asthma, increased asthma severity, viral upper respiratory tract infections, lower respiratory tract infections, obesity or hypertension.
Secondary objectives include determining whether there is a vitamin D dose response relationship with adverse health outcomes by:

  • Determining whether children with persistently low vitamin D level (low vitamin D level at more than one time point) are at higher risk of these adverse health outcomes than children with transiently low vitamin D level (low vitamin D level at only one time point).

  • Determining whether children with lower vitamin D levels (as a continuous variable) are at higher risk of these adverse health outcomes.


The cohort that will be followed will be those recruited via TARGet Kids! as part of a cross-sectional study of vitamin D deficiency.  This study will be a longitudinal cohort study to assess vitamin D level and health outcomes annually during their regularly scheduled primary healthcare visits for 4 years in the previously established cohort of healthy children 1 to 5 years of age. 



Importance of the Study


Because of Canada’s northern latitude, understanding vitamin D deficiency and associated preventable health problems is of major importance to Canadian children and their parents.   Low vitamin D levels may be implicated in some of the most common health issues during childhood including fractures, asthma, respiratory infections, obesity and hypertension.  Collectively, these conditions place an enormous burden on Canada’s health care system.  If low vitamin D level is making even a small contribution to these common health problems, measures to increase vitamin D levels may offer a significant benefit in reducing population wide morbidity and associated health service costs. Data from this longitudinal cohort study will provide essential evidence on early childhood low vitamin D levels and later adverse health outcomes.