Researchers have found that low levels of vitamin D are associated with lower lung function and increased medication use in children with asthma. The study published in the Journal of Allergy & Clinical Immunology also showed that vitamin D enhances the activity of corticosteroids.
Examining electronic medical records of 100 pediatric asthma patients, the researchers found that 47% of patients had vitamin D levels considered insufficient—below 30 µg/mL. Another 17% had levels below 20 µg/mL, which is considered deficient. These levels, however, were similar to vitamin D levels found in the general population.
Patients low in vitamin D had low FEV1 and lower FEV1/FVC. Use of inhaled steroids, oral steroids, and long-acting beta agonists were all higher in patients low in vitamin D. The study also found that patients low in vitamin D generally had higher levels of IgE, a marker of allergy, and responded positively to more allergens in a skin prick test.
Additionally, researchers performed a series of laboratory experiments that indicated that vitamin D enhances the action of corticosteroids. After culturing some immune cells with the corticosteroid dexamethasone alone and others with vitamin D first, the researchers found that vitamin D significantly increased the effectiveness of dexamethasone.
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 Donald Leung, MD, PhD. “If future studies confirm these findings vitamin D may help asthma patients achieve better control of their respiratory symptoms with less medication.”