Lead Sponsor

St. Justine's Hospital

Age

1 - 5 years

Sex

ALL

Healthy Volunteers

No

•children aged 1-5 years
•physician-diagnosed asthma as per GINA guidelines
•upper respiratory tract infections as the main asthma exacerbation trigger
•≥4 respiratory infections in the past 12 months
•≥1 exacerbation requiring rescue oral steroids in the past 6 months or ≥2 in the previous 12 months.

•extreme prematurity (\<28 weeks gestation)
•infants \<12 months of age
•breastfed infants with no vitamin D supplementation
•recent (\<1 year) immigrants from countries where rickets and malnutrition prevalent
•other chronic respiratory disease (broncho-pulmonary dysplasia; cystic fibrosis)
•endocrine disorder of calcium/ vitamin D metabolism
•disorder/ disease with associated malabsorption (inflammatory bowel disease)
•kidney/ liver disease
•sickle cell anemia
•medications known to interfere with bone metabolism/ vitamin D levels
•vitamin D supplementation \>1000 IU/ day in past 3 months
•unable to attend medical visit in 3-4 months
•plan to leave the province during the next 6 months.