Vitamin D in asthma: Panacea or true promise?

Abstract

concentrations <30 ng/mL) at enrollment was associated with a modest increase in the risk of severe asthma exacerbations over a 4-year follow up period in members of the Childhood Asthma Management Program cohort. Although this observation seems to suggest an important role for vitamin D in reducing exacerbation risk, we are unable to determine from this study the pathways through which the outcome is mediated. As noted by the authors, thestudyislimitedbytheabsenceofrepeatedvitaminDmeasurements over time, an issue that limits our ability to understand the extent to which fluctuations in vitamin D levels over time (because of seasonal, lifestyle, and demographic variables) might be relevant to the observed effect. Of note, the benefit with regard to exacerbations seemed to be accrued independent of significant effects of vitamin D status on markers of atopy or airway hyperresponsiveness,andinthesettingofonlysmalleffectsonabsolute FEV1. Although the exact nature of the relationship betweenvitamin D and severe exacerbations remains unclear, and although 1 limitation of the dataset the authors analyzed is the absence of specific data regarding respiratory tract infections, these findings suggest an effect that is mediated through enhanced resistance to respiratory tract infection rather than through direct modification of airway inflammation. This conclusion is supported by in vitro data showing that vitamin D is important in inducing the production of antimicrobial peptides, including cathelicidin, 8,9 as well as by an analysis of