Vitamin D and childhood asthma: causation and contribution to disease activity

Purpose of review To review the literature of the past 18 months (April 2017 through September, 2018) relating to vitamin D and childhood asthma. Recent findings A combined analysis of two clinical trials of maternal vitamin D supplementation trials showed a significant protective effect of vitamin D supplementation trials in the primary prevention of asthma and recurrent wheeze up to age 3 years. Secondary analyses from these trials have also suggested that initial maternal vitamin D status could affect the response to supplementation during pregnancy, with the biggest protective effect in children born to mothers with initial 25hydroxyvitamin D (25OHD) levels of at least 30 ng/ml. A postnatal, 6-month vitamin D supplementation trial in black, premature babies showed a 34% decreased risk of recurrent wheezing at 1 year among the infants who received supplementation. An individual patient data meta-analysis of published clinical trials concluded that vitamin D supplementation decreased the risk of asthma exacerbations in those with 25OHD levels less than 10 ng/ml. Results of observational analyses on primary prevention of asthma and in prevention of exacerbations remain mixed, with the bulk of the evidence suggesting that there is a protective effect of higher vitamin D levels. Summary Evidence continues to accumulate that vitamin D supplementation helps to prevent the development of asthma and recurrent wheeze in early life, and may also help in the management of asthma. The level(s) of circulating vitamin D that maximizes these effects remains to be identified.

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