There is “high quality” evidence that taking an oral vitamin D supplement in addition to standard asthma medication is likely to reduce severe asthma attacks, according to a Cochrane review.
Researchers said low blood levels of vitamin D had previously been linked to increased risk of asthma attacks and there was growing interest in its potential role in asthma management because it might help to reduce upper respiratory infections that can lead to exacerbations.
“This is an exciting result, but some caution is warranted”
They reviewed seven trials, involving 435 children, and two studies, involving 658 adults. The majority of patients had mild to moderate asthma, and a minority had severe asthma.
Most people continued to take their usual asthma medication while participating in the studies. The studies lasted for between six and 12 months.
The researchers found that giving an oral vitamin D supplement reduced the risk of severe asthma attacks requiring hospital admission or emergency department attendance from 6% to around 3%.
They also found that vitamin D supplementation reduced the rate of asthma attacks needing treatment with steroid tablets. These results were based largely on trials in adults.
However, they found that vitamin D did not improve lung function or day-to-day asthma symptoms.
Vitamin D supplements may reduce asthma attacks
Lead author Professor Adrian Martineau, from the Asthma UK Centre for Applied Research at Queen Mary University of London, said: “We found that taking a vitamin D supplement in addition to standard asthma treatment significantly reduced the risk of severe asthma attacks, without causing side effects.”
He added: “This is an exciting result, but some caution is warranted. First, the findings relating to severe asthma attacks come from just three trials. Further vitamin D trials in children and in adults with severe asthma are needed to find out whether these patient groups will also benefit.
“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,” he said.
Dr Imran Rafi, chair of clinical innovation and research at the Royal College of GPs, said: “It is encouraging that this research has so far shown some clinical evidence in reducing rates of severe asthma attacks among adults.
“However, more work still needs to be done in gathering the evidence, particularly around effectiveness for young people and children – especially as it currently affects as many as one in 11 children,” he said.
He added: “It is still too early to make general recommendations on prescribing vitamin D to patients with asthma, but we look forward to seeing the results of further rigorous clinical trials both in adults and children so that we gain a better understanding of this potential method of treatment.”