A new study shows that vitamin D supplements given to asthma patients do not reduce the incidence and severity of colds, despite previous studies showing they significantly reduced asthma exacerbations. The research paper, entitled “Vitamin D Supplementation and the Risk of Colds in Patients with Asthma,” was published online in the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine.
The research team had previously observed that vitamin D supplementation generated a 40% reduction in asthma exacerbations. Colds are a common trigger for exacerbations, so the scientists hypothesized that vitamin D, an immune system modulator, could also positively impact the frequency and severity of colds in these individuals. “Other studies of vitamin D and colds have produced mixed results. Most of those studies were conducted among healthy patients. We wanted to ask the same question of a patient population in which the impact of a cold carries greater risk,” said Loren C. Denlinger, MD, Associate Professor of Medicine at the University of Wisconsin, in a press release.
The scientists conducted a double-blind trial, “AsthmaNet Vitamin D Add-on Therapy Enhances Corticosteroid Responsiveness (VIDA),” involving 408 adults with mild to moderate asthma, tapering from a low-dose corticosteroid (ICS) therapy and showing vitamin D deficiency, which has been linked to susceptibility to respiratory infections. The patients were assigned to two groups, one receiving vitamin D supplements and the other on placebo treatment for 28 weeks.
About 50% of the patients had colds during the trial, and the severity of their symptoms was assessed using the Wisconsin Upper Respiratory Symptom Survey-21 (WURSS-21). Results showed that 82% of patients in the vitamin D group managed to achieve levels of vitamin D sufficiency within 12 weeks, but this sufficiency had no effect on the frequency or severity of their colds, or differences relative to patients in the placebo group. Moreover, African-American patients, who presented the lowest baseline levels of vitamin D, experienced more colds despite receiving the vitamin treatment.
The researchers, surprised by the results, theorize that vitamin D supplementation reduces asthma exacerbations because patients with sufficient vitamin D levels are more inclined to trigger inflammatory responses that reduce the risk of lower airway infections. Such infections are responsible for exacerbations.
Despite some limitations in the study, the researchers concluded, “Restoration of vitamin D sufficiency does not impact cold severity in patients with mild to moderate asthma undergoing an ICS dose reduction, and may increase the rate of symptomatic colds in patients with the lowest baseline levels of vitamin D.”
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