A daily dose of Vitamin D halves the risk of severe asthma attacks, a new study has shown.

Asthma patients who suffer from severe attacks, or exacerbations, were at a lower risk of having an attack and less likely to need hospital treatment if they had been taking regular doses of the vitamin, trials carried out by a Cochrane Review showed. They were also less likely to need treatment with steroid tablets.

Asthma is a chronic respiratory disease that affects around 300 million people worldwide, causing wheezing, coughing, chest tightness and shortage of breath.

Vitamin D in children and adults has been linked to lowering the risk of asthma attacks. Evidence suggests it may help prevent respiratory infections, such as the common cold, which can lead to exacerbations in patients.