High-dose vitamin D administered from the 24th week of pregnancy had no effect on a child’s risk for asthma at age 6, according to study results published in the Journal of the American Medical Association.

Asthma rates in children born to mothers randomly assigned to receive either standard care (vitamin D, 400 IU/d) or high-dose vitamin D (an additional 2400 IU/d) were examined annually for up to 6 years. Rates of asthma (termed persistent wheeze during the first 3 years of life and asthma thereafter) was diagnosed by study pediatricians who followed a predefined validated diagnostic algorithm and compared both groups.

Of the 581 children enrolled in the study, 545 completed yearly follow-up visits and were analyzed in the study. Asthma was diagnosed in 23 of 274 children (8%) in the high-dose vitamin D group compared with 18 of 268 children (7%) in the placebo group. Furthermore, an analysis of the yearly prevalence of persistent wheeze or asthma through age 6 showed that vitamin D supplementation had no effect (odds ratio, 0.87; 95% CI, 0.59-1.28; P =.48). No significant differences in lung function outcome, bronchial reactivity, fractional exhaled nitric oxide concentration, allergic sensitization, or rhinitis were observed between groups.

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“High-dose compared with standard-dose vitamin D supplementation during pregnancy was not associated with the child’s risk of asthma by the age of 6 years, at which time a diagnosis can be established using traditional measures,” the researchers wrote. “The possible clinically important protective effect of vitamin D on persistent wheeze at the age of 3 years was not found at the age of 6 years.”

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Brustad N, Eliasen A, Stokholm J, et al. High-dose vitamin d supplementation during pregnancy and asthma in offspring at the age of 6 years [published March 12, 2019]. JAMA. doi:10.1001/jama.2019.0052