Vitamin D may prevent influenza A in schoolchildren

Vitamin D supplementation during the winter may reduce the incidence of influenza A, especially in specific subgroups of schoolchildren, says a new study.

In the randomized controlled trial, the incidence of influenza A was compared in 430 schoolchildren (aged 6–15 years) taking vitamin D3 supplements (1,200 IU /day) with a group taking placebo during four months (1). The results showed a significant preventive effect against influenza A in children supplementing vitamin D, although no significant difference was observed for influenza B.

The preventive effect of vitamin D was consistent and more prominent in some subgroups of children, including those who had not been taking vitamin D supplements other than the study and children who did not have asthma. Children with asthma may be more susceptible to influenza. However, asthma attacks were also prevented by vitamin D3 supplementation.

The researchers suggested that vitamin D supplementation possibly reduced the risk of influenza A by enhancing innate immunity. They commented that further studies need to include a larger sample size of schoolchildren without comorbidities to determine the optimal dose and duration of vitamin D supplementation by measurement of serum 25-hydroxyvitamin D.

1. Urashima M. et al. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. AJCN. 2010.