Overall, supplementation resulted in a 30% reduction in the rate of asthma attacks requiring treatment with steroid tablets or injections.
Additionally, the team also recorded a 50% reduction in the risk of experiencing at least one asthma attack requiring hospitalisation.
“These results add to the ever growing body of evidence that vitamin D can support immune function as well as bone health,” said Dr Adrian Martineau, clinical professor of Respiratory Infection and Immunity at Queen Mary University of London (QMUL).
“Vitamin D is safe to take and relatively inexpensive so supplementation represents a potentially cost-effective strategy to reduce this problem.”
‘A precision medicine approach’
The review’s findings have led two New Zealand researchers to suggest in an accompanying comment piece that future studies should look at identifying whether characteristics such as 25(OH)D level or asthma severity can predict which patients might preferentially respond to treatment.
Results from this analysis, which suggests this is the case, opens up the possibility of specific patient characteristics representing a treatable trait, allowing a precision medicine approach to be implemented.”
Causal links between low serum vitamin D concentration and a wide range of disorders and diseases including cardiovascular disease, metabolic disorders, autoimmune diseases, and inflammation have been put forward in the past.
However, this has been compounded by highly promising results identified from observational studies that have either not been tested or not replicated in most of the randomised controlled trials.
Study findings
For this systematic review and meta-analysis, the team from Queen Mary University of London (QMUL) searched a number of databases for vitamin D3 or vitamin D2 supplementation and reported incidences of asthma exacerbation.
The team’s use of individual participant data allowed them to query the extent to which different groups respond to vitamin D supplementation, in more detail than previous studies.
The primary outcome was the incidence of asthma exacerbation requiring treatment with systemic corticosteroids.
Analytical methods were used to determine whether effects of vitamin D on risk of asthma exacerbation varied according to factors such as Vitamin D metabolite concentration, vitamin D dosing regimen and use of inhaled corticosteroids.
Findings revealed that the 30% reduction in asthma attacks that needed treatment represented a decrease from 0.43 events per person per year to 0.30.
The 50% reduction in experiencing at least one asthma attack requiring hospitalisation represented a decrease from 6% of people experiencing such an event to 3%.
Additional results found Vitamin D supplementation to be safe at the doses administered.
No cases of excessively high calcium levels or renal stones were seen, and serious adverse events were evenly distributed between participants taking vitamin D and those on placebo.
“Our results are largely based on data from adults with mild to moderate asthma: children and adults with severe asthma were relatively under-represented in the dataset, so our findings cannot necessarily be generalised to these patient groups at this stage,” said first author on the paper Dr David Jolliffe from QMUL.
“Further clinical trials are on-going internationally, and we hope to include data from them in a future analysis to determine whether the promise of today’s results is confirmed in an even larger and more diverse group of patients.”
Source: The Lancet
Published online ahead of print: doi.org/10.1016/S2213-2600(17)30306-5
“Vitamin D supplementation to prevent asthma exacerbations: a systematic review and meta-analysis of individual participant data.”
Authors: Adrian Martineau et al.