Adding a vitamin D supplement to the standard treatment for asthma reduced the risk of attacks significantly and did not cause side effects.
A Cochrane Review suggests that patients with asthma who take vitamin D supplements can reduce the number and severity of attacks, researchers reported here at the annual meeting of the European Respiratory Society.
The risk of severe attacks fell from 6% to 3% in patients who had a vitamin D boost for six months to a year.
Dr. Adrian Martineau from Queen Mary University of London said that they do not suggest people to quit their asthma treatment and just have the supplements without knowing whether or not you have vitamin D deficiency.
In the United Kingdom, 5.4 million people are being treated for asthma - that is one in 11 of the population.
Unfortunately, the review can't tell us whether everyone with asthma would benefit from taking vitamin D, or only people whose vitamin D levels are low.
No improvements in everyday asthma symptoms were found with vitamin D supplementation, nor did the supplements improve patients' lung function.
The lead author also added that further analyses need to be carried out in order to make sure that these supplements are what asthma patients need. This resulted in less trips to the emergency department due to severe asthma attacks.
Low blood levels of vitamin D in the blood have already been linked to an increased risk of having asthma attacks. The study involved the intake of vitamin D supplements alongside usual asthma medication.
GP Dr Rebecca Normansell said: "We would recommend anybody to take the simple blood test to determine their vitamin D levels, and to talk to a GP or pharmacist for advice".
An independent review by the Cochrane research body of nine clinical trials found it also cut the rate of asthma attacks needing steroid treatment.
The researchers found that consuming vitamin D supplements orally helped reduce the risk of severe asthma attacks, which require visits to the hospital.
"First, the findings relating to severe asthma attacks come from just three trials: most of the patients enrolled in these studies were adults with mild or moderate asthma".
"Further analyses to investigate these questions are ongoing, and results should be available in the next few months".
The study was carried out by researchers from several different universities, all of whom are part of the Cochrane Collaboration, an global network of researchers who review medical evidence according to high quality rules. He explained: "We don't want people giving up taking their asthma treatment". Some people in one study of low-dose vitamin D were found to have too much calcium in their urine, which over time can damage the kidneys.
This essential vitamin is also known as the "sunshine vitamin". However, doctors thought of a way of helping asthma patients.