Adding a high-quality vitamin D supplement to standard asthma medications can reduce the severity of asthma attacks.

A Cochrane Review of seven randomized trials involving more than 1,000 children and adults found that vitamin D reduced attacks and symptoms in both children and adults.
Several studies have linked low blood levels of vitamin D to an increased risk of asthma attacks in children and adults with asthma.

Experts have been interested 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 a worsening 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 in half — from 6 percent to around 3 percent.

They also found that vitamin D supplementation reduced the rate of asthma attacks needing treatment with steroid tablets.

"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," said lead author Professor Adrian Martineau of Queen Mary University of London.

Asthma is a chronic inflammatory disease that causes wheezing, tightness in the chest, and breathlessness.

According to the Centers for Disease Control, 1 in 12 Americans has asthma — about 25 million — and the numbers are increasing.