Vitamin D levels linked to lung function in asthmatic children
MedWire News: Vitamin D insufficiency is common in children with asthma, with lower levels of the vitamin associated with greater use of corticosteroids and poorer lung function, US researchers have found.
Writing in the Journal of Allergy and Clinical Immunology, Donald Leung (National Jewish Health, Denver, Colorado) and team explain: “Although multiple studies have examined maternal vitamin D status and subsequent wheezing in offspring, there are limited data on vitamin D levels in children with asthma.”
Furthermore, they add that “there is little knowledge about clinical variables associated with vitamin D insufficiency in asthmatic children.”
To investigate, the researchers studied vitamin D levels, as indicated by serum levels of 25-hydroxyvitamin D, in 100 asthmatic children aged up to 18 years who attended their center between 2008 and 2009.
They also studied the effects of vitamin D on dexamethasone (DEX) induction of mitogen-activated protein kinase phosphatase (MKP)-1 and interleukin (IL)-10 in peripheral blood mononuclear cells (PBMCs) in vitro.
The researchers found that 47% of the children had insufficient levels of vitamin D (less than 30 ng/ml) and 17% had vitamin D deficiency (less than 20 ng/ml).
Vitamin D levels were significantly inversely associated with immunoglobulin E levels and the number of positive aeroallergen skin prick test responses, and significantly positively correlated with FEV1 percent predicted and FEV1/forced vital capacity ratio.
The team also found that vitamin D levels were significantly inversely associated with the use of inhaled and oral steroids.
In vitro, levels of MKP-1 and IL-10 induced by vitamin D plus DEX were significantly higher than those induced by DEX alone, indicating that vitamin D had a significant influence on corticosteroid-mediated anti-inflammatory response.
Leung and team conclude: “Corticosteroid use and worsening airflow limitation are associated with lower vitamin D serum levels in asthmatic patients.”
They add: “Our study suggests that vitamin D supplementation might potentiate anti-inflammatory function of corticosteroids in asthmatic patients and thereby improve asthma control.”
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By Mark Cowen