Asthma, Corticosteroid Dose, and Vitamin D
If the media weren’t preoccupied with cyber-espionage charges by the US, flooding in the Balkans, and the impact of global warming on the Antarctic polar cap, you might be reading about vitamin D, respiratory function, and asthma.
Asthma is a common disorder where the airways of the lungs become inflamed and hyper-reactive. The resulting constriction makes it difficult to breathe. Asthma is a complex dysfunction involving over 90 genes and >800 single nucleotide polymorphisms (SNPs), none of which singularly contribute to susceptibility. Many factors can initiate a reaction, including allergens and environmental irritants like smoke particulates. Since 2001, the prevalence of asthma in the US has increased from 1.5% in 2001 to 8.4% in 2010.
Reduced vitamin D levels are associated with impaired lung function. In a cohort of 25,616 Norwegian adults, Mai and colleagues reported low vitamin D status (< 50 nmol/L) was not associated with incident asthma in most adults but incident risk was higher in men without allergy having low vitamin D status. In children with asthma, low serum 25(OH)D3 levels are associated with increased corticosteroid use.
The VIDA (Vitamin D Add-on Therapy Enhances Corticosteroid Responsiveness in Asthma) trial was a randomized, placebo-controlled trial (RCT) in adults with asymptomatic asthma using 320 µg/d ciclesonide (a corticosteroid). Participants with serum 25(OH)D3 concentrations < 75 nmol/L were randomized to placebo or vitamin D supplementation. Mean baseline serum 25(OH)D3 concentration was ~ 50 nmol/L with >50% of the study group meeting Institute of Medicine definition of vitamin D sufficient (> 50 nmol/L). After 12 wk, serum 25(OH)D concentrations increased to an average just over 100 nmol/L in the supplemented group. The addition of vitamin D to ciclesonide did not significantly reduce the rate of first treatment failure compared to placebo. However, several caveats are noteworthy. First, serum vitamin D status increased to > 75 nmol/L in 9% of the placebo group; indicating they were either spending more time in the sunshine or using vitamin D supplements. Second, serum 25(OH)D concentrations did not increase in all participants being given vitamin D. The authors note that approximately 25% were non-responders. This may be attributable to non-compliance, baseline status, or genetic differences in vitamin D metabolism. Vitamin D supplementation was associated with a statistically significant tapering of corticosteroid use, down to as little as 25% of the original dose. .
In conclusion, while the VIDA study did not find vitamin D status significantly changed the rate of first treatment failure in patients being treated for asthma, it is exciting to consider that improving vitamin D status might decrease corticosteroid use by 75%. There are many other examples where improved nutrient status can help combat rising health care costs.
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