Abstract
Asthma is a chronic respiratory disease that poses significant individual, social, financial and healthcare burdens. Physicians and researchers have recommended 25-hydroxy vitamin D supplementation, in combination with prescribed medication, as a potential means of reducing asthma severity. This systematic review focuses on the association between 25-hydroxy vitamin D levels and lung function in both children and adults with asthma. We identified published work by searching MEDLINE via PubMed, using regular search terms related to 25-hydroxy vitamin D and asthma. Fourteen studies were screened out of 643 eligible citations from MEDLINE research that involved 65 children and 951 adults. A strong positive association was observed in four studies, whereas five showed a moderate association, and two had no correlation. The majority of studies found a negative correlation between 25-hydroxy vitamin D deficiency and mild, uncontrolled and partly controlled asthma. 25-hydroxy vitamin D 25 OH values were below 20 ng/ml in the majority of studies, and those with uncontrolled severe asthma showed the lowest values.