Research Title: The effect of vitamin D replacement on airway reactivity, allergy and inflammatory mediators in exhaled breath condensate in vitamin D deficient asthmatic children.

Introduction: Vitamin D seems to play a role in allergic and asthmatic reactions as an immunomodulator. Asthma disease involves inflammatory process in the lower respiratory tract and airway hyperreactivity.

Aim: To assess the effect of Vitamin D replacement on airway reactivity, and allergy and inflammatory mediators in exhaled breath condensate in vitamin D deficient asthmatic children.

Design: Double blind placebo control prospective study comparing the effect of Vitamin D replacement and placebo on airway reactivity, allergy and inflammatory mediators in exhaled breath condensate in asthmatic pediatric population with vitamin D deficiency.

Participant selection: The study group will consist of pediatric patients (age 6-18 years) followed and treated at the Pediatric Pulmonary Unit at the investigators hospital.

Patients with mild-moderate asthma with low or insufficient vitamin D levels that are currently not receiving anti-inflammatory treatment will be recruited.

Sample size: 60 participants in the two groups (30 receiving Vitamin D and 30 receiving placebo).

Intervention: Vitamin D (14000 units) or placebo will be provided in a similar appearance preparation once weekly for 6 weeks between visit two and three.

Three visits will be conducted. Each subject will undergo evaluation including a respiratory questionnaire (visit 1), methacholine challenge test with determination of PC20 (visit 1 or 2 and visit 3), exhaled nitric oxide (eNO) (visit 2, 3), and exhaled breath condensate (EBC) (visit 2,3). Venous blood will be analyzed for complete blood count + eosinophils (visit 1, 3), IGE levels (visit 1, 3), and Vitamin D levels (visit 1, 3). Prick skin test for inhaled allergens will be performed (visit 2, 3).

Primary end point: Airway reactivity as assessed by methacholine challenge test.

Secondary outcome parameters: All other parameters are the secondary end points.

Inclusion Criteria:

• 6-18 years
• Mild-moderate asthma
• No anti inflammatory treatment over the past 2 weeks

Exclusion Criteria:

• Any Chronic Lung Disease
• Febrile Illness in last 2 weeks
• FEV1 < 65% in study day
• Bronchodilators over the past 24 hours prior to each study
• Participation in any other clinical studies over the past 4 weeks