A recent study concluded that vitamin D can prevent severe asthma issues. This study looked at the results of 9 other studies on vitamin D and asthma and found that these results applied to patient with more severe asthma. It was also found that patient had a less hospital visits because of severe asthma issues. It is thought that this may be because vitamin D may help with the immune system.
Can vitamin D reduce asthma attacks? An interview with Professor Adrian Martineau