While the underlying causes of asthma remain unclear, symptoms of asthma - such as wheezing, shortness of breath, coughing, and chest pain and tightness - can be triggered by exposure to allergens and irritants. These include grass or weed pollen, molds, dust mites, and smoke.
There is no cure for asthma, but there are medications that can help manage symptoms and reduce the risk of life-threatening asthma attacks.
Now, researchers suggest adding vitamin D supplements to the treatment regimen for asthma patients could further reduce the risk of severe asthma attacks.
Lead author Prof. Adrian Martineau - from the Asthma UK Centre for Applied Research at Queen Mary University of London in the United Kingdom - and colleagues recently presented their findings at the at the European Respiratory Society International Congress 2016.
Vitamin D supplements reduced asthma-related hospitalization
The team notes that previous studies have associated low vitamin D levels with greater risk of asthma attacks in people with the respiratory condition.
As such, researchers have increasingly investigated whether vitamin D supplementation might benefit asthma patients.
For their review, Prof. Martineau and colleagues analyzed the data of nine studies - lasting between 6-12 months - that assessed how vitamin D supplementation influences asthma symptoms and asthma attacks.
Seven of the studies included 435 children, while two included 658 adults. Most participants had moderate to severe asthma, though a small number had severe asthma. The majority of subjects continued their standard treatment.
The risk of hospital admission or emergency department visits due to severe asthma attacks was reduced from 6 percent to 3 percent with oral vitamin D supplementation, the researchers report, and no severe side effects were identified.
What is more, the team found that vitamin D supplementation reduced the need for steroid treatment for asthma attacks; steroid treatment may be administered to reduce airway inflammation when a patient's inhaler is no longer effective.
No improvements in everyday asthma symptoms were found with vitamin D supplementation, nor did the supplements improve patients' lung function.
'Exciting' findings, but caution warranted
Prof. Martineau hails these results as "exciting," but because the study has some important limitations, he says the results should be interpreted with caution.
He notes that first of all, most of the patients enrolled in the studies were adults with mild to moderate asthma, so further research is warranted to determine whether vitamin D supplementation is effective for children and adults with severe asthma.
"Second, it is not yet clear whether vitamin D supplements can reduce risk of severe asthma attacks in all patients, or whether this effect is just seen in those who have low vitamin D levels to start with," says Prof. Martineau.
"Further analyses to investigate these questions are ongoing, and results should be available in the next few months."
Vitamin D for the management of asthma: Cochrane Database of Systematic Reviews 2015, Adrian Martineau et al., presented at the European Respiratory Society International Congress 2016, 5 September 2016.
European Respiratory Society news release, accessed 6 September 2016 via AlphaGalileo.
Additional source: CDC, Asthma, accessed 6 September.