Vitamin D does not reduce colds in asthma patients

http://www.eurekalert.org/pub_releases/2015-11/ats-vdd112315.php

Public Release: 23-Nov-2015
Vitamin D does not reduce colds in asthma patients
American Thoracic Society

Vitamin D supplements do not reduce the number or severity of colds in asthma patients, according to a new study published online ahead of print publication in the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.

Loren C. Denlinger, MD, PhD, associate professor of medicine at the University of Wisconsin, and colleagues conducted a randomized, controlled trial of adults with mild-to-moderate asthma. Among African Americans in the study, those receiving supplemental vitamin D, rather than a placebo, experienced more colds.

The findings surprised the researchers who had previously published research showing a 40 percent reduction in asthma exacerbations in patients with a vitamin D deficiency who achieved normal levels of the vitamin with supplements. Because colds often trigger exacerbations, they hypothesized that vitamin D supplementation would reduce colds and cold severity.

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The researchers analyzed separately the results of the 82 percent of participants receiving supplements who achieved vitamin D sufficiency within 12 weeks. Achieving sufficiency made no difference in number of colds or their severity this group experienced.

The researchers wrote that one possible explanation for the unexpected finding: asthma patients with low vitamin D levels may be more likely to experience upper respiratory infections asymptomatically than those with normal levels of vitamin D, which is known to trigger an inflammatory response. This inflammatory response may, in turn, reduce the risk of lower airway infections, which are triggers for asthma exacerbations.
[The inflammatory response is part of the immune system. Most of the symptoms of a cold are due to the bodies immune response.]

Although there are other reasons to recommend vitamin D supplements for asthma patients, including the fact that they are at greater risk for bone weakening, Denlinger said, "we can't recommend vitamin D for the prevention of colds."

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