Taking oral vitamin D supplements as well as standard asthma medication halves the rate of asthma attacks requiring hospital attendance, and cuts the likelihood an asthma attack will require treatment with systemic steroids by almost a third, a study published in Lancet Respiratory Medicine has found.
For the study, funded by the National Institute for Health Research, researchers combined data on 955 asthma patients who participated in seven randomised controlled trials testing the use of vitamin D supplements.
The results showed that vitamin D supplementation reduced the rate of asthma exacerbations treated with systemic corticosteroids when compared with placebo (0.30 events per person per year vs 0.43 events per person per year; P=0Â·03), and the proportion of people having at least one exacerbation requiring emergency department attendance and/or hospital admission (3% vs 6%; P=0Â·03).
Subgroup analysis revealed that vitamin D supplementation reduced the rate of asthma exacerbations treated with systemic corticosteroids compared to placebo in people with a baseline 25-hydroxyvitamin D of less than 25 nmol/L (0.19 events per person per year vs 0.42 events per person per year; P=0.046). However, vitamin D supplementation did not result in a statistically significant reduction in exacerbation rate in participants with baseline 25-hydroxyvitamin D of 25 nmol/L or higher.
The researchers cautioned that, due to the relatively small numbers of patients within sub-groups, they did not find definitive evidence to show that effects of vitamin D supplementation differ according to baseline vitamin D status.
David Jolliffe, one of the researchers from Queen Mary University of London, said: “Our results are largely based on data from adults with mild to moderate asthma: children and adults with severe asthma were relatively underrepresented in the dataset, so our findings cannot necessarily be generalised to these patient groups at this stage.”