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Low Vitamin D Levels Associated With More Asthma Symptoms, Medication Use DENVER -- April 16, 2010 -- Low levels of vitamin D are associated with lower lung function and greater medication use in children with asthma, according to a study published online this week in the Journal of Allergy & Clinical Immunology. The researchers also reported that vitamin D enhances the activity of corticosteroids, the most effective controller medication for asthma. "Asthmatic children in our study who had low levels of vitamin D were more allergic, had poorer lung function and used more medications," said Daniel Searing, MD, National Jewish Health, Denver, Colorado. "Conversely, our findings suggest that vitamin D supplementation may help reverse steroid resistance in asthmatic children and reduce the effective dose of steroids needed for our patients." The researchers examined electronic medical records of 100 paediatric patients with asthma who were referred to National Jewish Health. Overall, 47% of patients had vitamin D levels considered insufficient (<30 ng/mL) and 17% had levels considered deficient (<20 ng/mL). These levels were similar to vitamin D levels found in the general population. Patients low in vitamin D generally had higher levels of Immunoglobulin E and responded positively to more allergens in a skin prick test. Allergies to specific indoor allergens (dog and house dust mite) were higher in patients with low vitamin D levels. Low vitamin D also correlated with low forced expiratory volume in the first second (FEV1). Use of inhaled steroids, oral steroids and long-acting beta agonists were all higher in patients low in vitamin D. "Our findings suggest 2 possible explanations," said senior author Donald Leung, MD, of National Jewish Health. "It could be that lower vitamin D levels contribute to increasing asthma severity, which requires more corticosteroid therapy. Or, it may be that vitamin D directly affects steroid activity, and that low levels of vitamin D make the steroids less effective, thus requiring more medication for the same effect." The researchers performed a series of laboratory experiments that indicated vitamin D enhances the action of corticosteroids. They cultured some immune cells with dexamethasone alone and others with vitamin D first, then dexamethasone. The vitamin D significantly increased the effectiveness of dexamethasone. In one experiment, vitamin D and dexamethasone together were more effective than 10 times as much dexamethasone alone. The researchers also incubated immune-system cells for 72 hours with a staphylococcal toxin to induce corticosteroid resistance. Vitamin D restored the activity of dexamethasone. "Our work suggests that vitamin D enhances the anti-inflammatory function of corticosteroids," said Dr. Leung. "If future studies confirm these findings vitamin D may help asthma patients achieve better control of their respiratory symptoms with less medication." SOURCE: National Jewish Medical and Research Center E-mail this page to a friend or colleague! To print, use this version