Vitamin D supplementation may help prevent asthma if taken prenatally or given to children postnatally, according to a new study conducted in mice. Supplementation did not have a benefit if asthma was already established.
The researchers studied how vitamin D supplementation affected asthma following exposure to traffic-related air pollution (TRAP), which causes asthma exacerbations in children and is likely to promote asthma development in early life.
“Our results offer the first evidence that vitamin D deficiency specifically makes children susceptible to the effects of TRAP exposure,” says senior author of the study. “The data show that children and pregnant mothers exposed to high levels of TRAP would benefit most from taking vitamin D.
“These findings could have a tremendous public health impact, because in large cities in the United States, up to 45 percent of the population resides in zones that are most impacted by TRAP, and more than 30 percent of schools are located in high TRAP areas.”
Vitamin D insufficiency affects at least half of children and 39 percent of adults in the United States. Widespread vitamin D deficiency has long been thought to be a contributing factor to the rise in asthma that has occurred in the past 20 years. In addition, a recent study revealed that children who were vitamin D deficient and lived near major roadways were five times more likely to experience asthma exacerbations compared to children living in the same areas who were not deficient in vitamin D.
The study is published in the Journal of Allergy and Clinical Immunology, a publication of the American Academy of Allergy, Asthma, and Immunology.
The authors studied mice on a normal mouse chow diet. Half were given a normal water supply and half given a normal water supply with vitamin D added. All were exposed to diesel exhaust particles, a major component of traffic pollution.
The researchers found that TRAP exposure is associated with increased levels of interleukin 17A (IL-17a), a small molecule that induces inflammation and increases asthma severity. Given recent reports demonstrating that vitamin D suppresses IL-17 production, it is possible that vitamin D may have a direct impact on Th17 cells in the lungs following TRAP exposure, according to the senior author.
The findings support the need for a clinical trial to examine the effect of vitamin D supplementation in preventing asthma development in children exposed to high levels of TRAP. The senior author recommends that pediatricians and family physicians check vitamin D levels in infancy or early childhood, and that children take supplements as recommended by their physicians to keep vitamin D levels in the normal range.
Vitamin D Supplementation Helps Prevent Asthma in Mouse Study
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