Vitamin D3 supplementation significantly increased serum 25(OH)D levels and reduced the amount of missed school days (P=0.04) compared to placebo, a recent study has shown. Additional findings are published in Pediatric Allergy and Immunology

Interventional trials evaluating the role of vitamin D in childhood asthma have not been consistent, researchers explained. For this study, they conducted a double-blind, randomized, placebo-controlled trial to assess the effect of 15 weeks of vitamin D supplementation (2,000 IU/day) vs. placebo in Irish asthmatic children (n=44). Researchers measured lung function, subjective asthma control, and biochemical parameters of total vitamin D, allergy, immunity, airway inflammation, and systemic inflammation. Parents and guardians of the participants also completed a weekly diary during the study. 

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The data showed no significant difference in baseline 25(OH)D levels but a significant increase in median 25(OH)D in the vitamin D3 group vs. placebo was seen (5.75–105nmol/L vs. 52.5–57.5nmol/L; P<0.0001). No significant difference was seen between groups regarding subjective asthma control. Participants in the vitamin D3 arm had a significant reduction in school days missed due to asthma vs. placebo (1 vs. 5 days; P=0.04) and in levels of alkaline phosphatase vs. placebo (-3.4 vs. +16; P=0.037). 

Changes in subjective asthma control and lung function, especially percentage of forced expiratory volume in 1 second were non-significant  in the placebo group vs. the vitamin D3 group (+2.5 vs. -4; P=0.06). More investigation is warranted on the potential adverse effect of vitamin D deficiency, on growth and high serum 25(OH)D on pulmonary function, the authors concluded.

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