DO IT Trial: Vitamin D Outcomes and Interventions In Toddlers (DO IT)

Vitamin D can be made in the skin by exposure to sunlight and can be found in certain foods. Vitamin D levels are alarmingly low in many North American children. Several health issues have been linked with low vitamin D. These include colds caused by viruses and asthma attacks. However, no study has determined whether vitamin D supplementation can reduce the risk of these conditions in young children where they are most common and most severe. The goals of this study are to determine whether wintertime high dose vitamin D supplementation of preschoolers can prevent colds and asthma attacks. The investigators also aim to work out how much money would be saved by the health care system and society if preschoolers were routinely supplemented with Vitamin D during the winter. The investigators believe that preschoolers receiving 'high dose' vitamin D supplementation during the wintertime will be less likely to have colds, asthma attacks, and low vitamin D levels and will be less likely to use the medical system and keep their parents away from work.

Vitamin D, Randomized Controlled Trial, Child, Preschool, Dietary Supplements, Respiratory Tract Infections, Asthma

One drop per day (liquid), 400 IU, 4 to 9 months depending on date of enrollment and date of follow-up

One drop per day (liquid), 2000 IU, 4 to 9 months depending on date of enrollment and date of follow-up

Parents of enrolled children will be asked to obtain a nasal swab from their child and complete a symptom checklist with each URTI. Reverse transcriptase polymerase chain reaction will be performed on each sample. Samples will be tested for 18 common respiratory viruses using the ID-TagTM RVP assay using the Luminex xMAPTM system.

Parental reported URTI symptoms will be defined as two or more of fever, cough, runny nose, sore throat, headache, vomiting, feels unwell, muscle aches, ear ache or infection, poor appetite, not sleeping well, cranky/fussy, low energy or crying more than usual from a validated parent completed symptom checklist.

Asthma exacerbation will be defined as a wheezing episode in children with asthma as obtained from parent completed symptom checklist based on the International Study of Asthma and Allergies in Childhood (ISAAC).

Blood for serum levels will be drawn by trained pediatric phlebotomists from for determination of 25-hydroxyvitamin D. Total 25-hydroxyvitamin D will be measured from serum samples using a competitive two-step chemiluminescence assay.

Cost-consequence and cost-effectiveness analyses will be conducted using data from this clinical trial. A societal perspective will be employed as both direct health service utilization costs as well as indirect costs to families from URTI will be calculated for the 400 IU per day versus 2000 IU per day groups.

Weight and height will be measured at both study baseline and follow-up by trained research assistants. BMI will be determined by dividing the children's measured weight (kg) by height (m2). The BMI z-score [zBMI] will be determined using the World Health Organization Growth standards, standardized for age and sex.

Waist circumference will be measured at both study baseline and follow-up by trained research assistants. Waist circumference will be measured at the mid-axillary line above the right iliac crest. Waist circumference z-score will be calculated internally within the entire TARGet Kids! study cohort.

Blood for serum levels will be drawn by trained pediatric phlebotomists from for determination of total cholesterol, low-density lipoprotein [LDL] cholesterol, high-density lipoprotein [HDL] cholesterol and non-HDL cholesterol.

Inclusion Criteria: Healthy children by parental report Have reached their 1st birthday but not past their 6th birthday Present to a TARGet Kids! practice for routine primary healthcare prior to viral season (September through November) Parents provide informed consent to participate. Exclusion Criteria: Children with gestational age < 32 weeks Children with chronic illness (except for asthma) on parental report which is known to interfere with vitamin D metabolism and increase the risk of respiratory infection Children with a sibling participating in the study to reduce clustering effects.

Huey SL, Acharya N, Silver A, Sheni R, Yu EA, Pena-Rosas JP, Mehta S. Effects of oral vitamin D supplementation on linear growth and other health outcomes among children under five years of age. Cochrane Database Syst Rev. 2020 Dec 8;12(12):CD012875. doi: 10.1002/14651858.CD012875.pub2.

Aglipay M, Birken CS, Parkin PC, Loeb MB, Thorpe K, Chen Y, Laupacis A, Mamdani M, Macarthur C, Hoch JS, Mazzulli T, Maguire JL; TARGet Kids! Collaboration. Effect of High-Dose vs Standard-Dose Wintertime Vitamin D Supplementation on Viral Upper Respiratory Tract Infections in Young Healthy Children. JAMA. 2017 Jul 18;318(3):245-254. doi: 10.1001/jama.2017.8708.