Please select the eligibility criteria that correspond to the clinical trial below.
Title: DO IT Trial: Vitamin D Outcomes and Interventions In Toddlers
Brief Summary: 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.


Options:
A: Inclusion Criteria:

* 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.

Exclusion Criteria:

* 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.
B: Inclusion Criteria:

* 6 to 16 years old
* Physician-diagnosed asthma for at least one year
* At least one severe asthma exacerbation in the previous year
* Use of asthma medications (daily controller medication \[ICS or leukotriene inhibitor\] or inhaled β2-agonist \[at least three days per week\]) for at least six months in the previous year
* Vitamin D insufficiency (i.e., serum vitamin D (25(OH)D level \<30 ng/ml (75 nmol/L))
* FEV1 ≥70 % of predicted
* Positive bronchodilator response (i.e., increase in FEV1 ≥8% from baseline after inhaled short acting beta agonist or increased airway responsiveness to methacholine (PC20 ≤8 mg/ml if not on ICS or PC20 ≤16 mg/ml if on ICS)
* Study protocol (i.e., age-appropriate dose of Fluticasone and no other asthma controller medications) approved by the child's regular doctor
* Parental consent and child's assent to participate in the study.

Additional inclusion criteria applied after the run-in period, to be eligible for randomization:

* Adherence with ICS and study medication (≥75% use \[at least 21 of 28 days\]) during the run-in period
* Willingness to be randomized and complete study

Exclusion Criteria:

* Serum calcium \>10.8 mg/dl
* Serum 25(OH) D \<14 ng/ml (35 nmol/L)
* Chronic respiratory disorder other than asthma
* Severe asthma (intubation for asthma at any time OR ≥3 hospitalizations for asthma in previous year OR ≥6 severe asthma exacerbations in previous year)
* Hepatic/renal disease, rickets, malabsorption, or other diseases that would affect vitamin D metabolism
* Current smoking, or former smoking if ≥5 pack-years
* Immune deficiency, cleft palate or Down's syndrome
* Treatment with anticonvulsants or ≥1,000 IU/day of vitamin D2 or D3
* Chronic oral corticosteroid therapy
* Inability to perform acceptable spirometry
* Use of investigational therapies or participation in trials 30 days before or during the study
* Participant is currently breast feeding an infant
* Pregnancy
* Weight less than 10 kg
* Plans to move out of the study site area in the next year

Additional exclusion criteria applied after the run-in period:

* Any severe asthma exacerbation during the run-in period
* Need for asthma medications other than ICS and p.r.n. rescue inhalers during the run-in period
C: Inclusion Criteria:

1. Healthy children by parental report
2. Have reached their 1st birthday but not past their 6th birthday
3. Present to a TARGet Kids! practice for routine primary healthcare prior to viral season (September through November)
4. Parents provide informed consent to participate.

Exclusion Criteria:

1. Children with gestational age \< 32 weeks
2. 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
3. Children with a sibling participating in the study to reduce clustering effects.
D: Inclusion Criteria:

* Patients aged between 6 and 14 years old, of both sexes
* Diagnosis of mild / moderate persistent asthma (GINA step 2/3)
* Allergy mite (Dermatophagoides farinae and pteronyssinus + + + / + + + +)
* Levels of vitamin 25 (OH) D \<30 ng / ml
* Signature of the informed consent of one parent or a legal representative

Exclusion Criteria:

* Cardiovascular disease or systemic
* anatomical abnormalities
* Other respiratory diseases
* Taking probiotics and / or prebiotics in the previous 2 weeks
* Taking vitamin D or systemic corticosteroids within 4 weeks
* Participation in other clinical trials

Answer: C