Vitamin D supplements do not prevent severe asthma attacks in at-risk children, according to a study published in JAMA.

Earlier studies have suggested that vitamin D plays a role in reducing asthma attacks in children. However, the study published in JAMA is the first placebo-controlled clinical trial to test the relationship, according to the authors. 

The Vitamin D-Kids Asthma (VDKA) study followed approximately 200 children aged 6 to 16 years across 7 different hospital systems in the United States. All the children had at least 1 asthma attack the year before the study began. 

Half of the participants were randomized to receive either a placebo or 4000 IU of vitamin D per day. No one in the study knew which type of pill each participant was getting. All of the participants had vitamin D levels that were low enough that a supplement should have been effective, according to the authors. Children with severe vitamin D deficiency were excluded as it would be unethical to withhold the supplement.

The study showed that compared with the placebo, vitamin D did not reduce the number of asthma attacks the participants experienced. It also did not reduce their reliance on inhaled steroids. These results are contrary to findings from previous observational studies in Costa, Rica, the United States, Canada, and Puerto Rico. In those studies, children with naturally low vitamin D Levels appeared to have worse asthma, according to the authors of the current study. 

"With observational studies, you never know—is vitamin D causing asthma to be worse or do kids with worse asthma end up having lower vitamin D?" lead author and chief of pediatric pulmonary medicine at UPMC Children's Hospital of Pittsburgh, Juan C. Celedón, MD, said in the press release.

Even with the rigor of the study, the authors said that conclusions cannot be drawn about how very low vitamin D levels contribute to asthma attacks. However, those children should receive supplements regardless due to the known effect on bone health, according to the study. 

Reference:

Compared to placebo, vitamin D has no benefit for severe asthma attacks, study finds (Press Release) Pittsburg, PA, August 25, 2020 ScienceDaily, accessed August 26, 2020