Researchers have found evidence suggesting that taking vitamin D supplements along with asthma medication can reduce severe symptoms. However, they added that further analysis is required before giving patients official advice. The findings were published Tuesday in the Cochrane Library journal.

“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,” the review’s lead author Adrian Martineau from the Queen Mary University of London, said in a statement.

The researchers analyzed data from seven clinical trials involving a total of 435 children and two studies with 658 adult participants. The data used was geographically diverse coming from Canada, India, Japan, Poland, the United Kingdom and the United States. The patients were suffering from mild to moderate asthma with a minority having severe asthma. The studies lasted for a period of six to 12 months.

Low levels of vitamin D in the blood have been linked to an increased risk of asthma attacks in children and adults with the chronic disease. The participants continued to take their standard asthma medication during the period of the studies.

The researchers found that consuming vitamin D supplements orally helped reduce the risk of severe asthma attacks, which require visits to the hospital. It helped reduce visits to the emergency room from 6 percent to 3 percent. Taking vitamin D supplements also reduced the need for treating patients with steroids.

However, taking vitamin D supplements along with standard asthma medication did not improve lung function or the usual asthma symptoms. The findings were largely based on trials conducted on adults.

“This is an exciting result, but some caution is warranted. 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 vitamin D trials in children and in adults with severe asthma are needed to find out whether these patient groups will also benefit,” Martineau said in the statement.

“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. Further analyses to investigate these questions are on-going, and results should be available in the next few months,” he added.

In the U.S., 17.7 million adults and 6.3 million children have asthma, according to the Centers for Disease Control and Prevention. The disease causes wheezing, breathlessness, chest tightness and coughing.