In a study conducted in Mongolian schoolchildren, an international research team found that daily vitamin D supplementation decreased the risk of respiratory infections among children who had low blood levels of vitamin D at the start of the study.
“Our randomized controlled trial shows that vitamin D has important effects on infection risk,” said Carlos Camargo, MD, of Massachusetts General Hospital (MGH), the study’s corresponding author.
“In almost 250 children with low blood levels of vitamin D during winter, we found that taking a daily vitamin D supplement cut in half the risk of a respiratory infection,” Camargo stated.
Several recent investigations have suggested that vitamin D – best known for its role in the development and maintenance of strong bones – has additional important roles, including in immune function.
Since vitamin D is naturally produced by the body in response to sunlight, maintaining adequate levels in winter is particularly challenging in areas such as the northern U.S. and Canada that have significant seasonal variations in daily sunlight.
The current study analyzed data from the Blue Sky Study, conducted in Ulaanbaatar, Mongolia, by a team led by Harvard investigators in collaboration with local health researchers.
Mongolians are known to be at high risk for vitamin D deficiency, especially during winter, and the Blue Sky Study followed schoolchildren, all of whom were found to have low blood levels of 25-hydroxyvitamin D (25OHD), which is considered the best measure of vitamin D status, at the study's outset.
In the current study, Camargo and colleagues compared the number of winter respiratory infections among a group of children who received daily doses of vitamin D added to locally produced milk with that of a control group receiving the same milk without added vitamin D.
Based on reports from their parents, the children receiving vitamin D had about half the incidence of respiratory infections that the control group had.
“Our study design provides strong evidence that the association between low vitamin D and respiratory infections is causal and that treating low vitamin D levels in children with an inexpensive and safe supplement will prevent some respiratory infections,” says Camargo, a professor of Medicine at Harvard Medical School.
The findings will appear in the journal Pediatrics.