A new Cochrane Review has found evidence from randomised trials that taking an oral vitamin D supplement in addition to standard asthma medication is likely to reduce severe asthma attacks.

Asthma is a common chronic disease affecting about 300 million people worldwide. The symptoms of asthma include wheezing, coughing, chest tightness and shortness of breath.

Low blood levels of vitamin D have been linked to increased risk of asthma attacks in children and adults with asthma. There has been a growing interest in the potential role of vitamin D in asthma management because it might help to reduce upper respiratory infections (such as the common cold) that can lead to exacerbations of asthma.

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.