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Tuesday, April 13, 2010

Vitamin D levels tied to lung function and steroid sensitivity

Is it sunscreen? Or video games? Can we blame it on the weather or overeating? There is mounting evidence that vitamin D deficiency/insufficiency may be a critical factor in healthy lung function and far more common than we know.

Vitamin D and lung function in patients with asthma are the topics of articles by Sutherland et al. (Am J Respir Crit Care Med 2010, 181:699-704) and Freishtat et al. (J Pediatr 2010, doi:10.1016/j.jpeds.2009.12.033).

Sutherland and colleagues look at vitamin D2 and D3 levels, FEV1, and PC20 FEV1 in a small sample comprised of ICS-treated and –untreated asthmatic subjects. They report a significant finding of 22 ml mean increase in FEV1 for each ng/ml increase in vitamin D levels. This effect was most prominent in the ICS-untreated subjects. And there's more. Deficient/insufficient vitamin D levels were correlated to greater airway hyperreactivity and obesity. The authors also show that vitamin D improved in vitro glucocorticoid responses across both groups and suggest that serum vitamin D levels be assessed in adult patients with asthma that have poor response to ICS therapy.

Freishtat et al. present results from a cross-sectional study of African American (AA) youth with and without asthma from inner-city Washington, DC. Confirming previous research that AA individuals are more likely to be vitamin D deficient than other races, they report that vitamin D levels were significantly lower in the subjects with asthma as compared to the subjects without asthma, and prevalence of vitamin D insufficiency was significantly greater. Freishtat and colleagues point out that their AA cohort has lower levels of vitamin D than that reported recently for a Costa Rican cohort. They suggest that many factors could contribute to this, such as dark skin, obesity, high rates of poverty and northern latitude.

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