medwireNews: Supplementation with vitamin D, particularly in winter, appears to reduce a child's risk for contracting acute respiratory infections (ARIs) by almost 50%, show results from a Mongolian study.
Based on findings from observational studies suggesting that low serum levels of 25-hydroxyvitamin D (vitamin D) are associated with an increased incidence of ARIs, Carlos Camargo (Harvard Medical School, Boston, Massachusetts, USA) and team carried out a randomized study to assess whether supplementing children with vitamin D could reduce their risk for such infections.
In total, 247 Mongolian children, aged 10 years on average, were recruited to take part in the study. Children assigned to the intervention group (n=143) were given tasteless and colorless (for double blinding purposes) vitamin D3 300 IU/day added to milk. The children in the control group (n=104) were given the same amount of unfortified milk.
The children were given the milk for 3 months between January and March. At the end of this period the researchers assessed how many ARIs, defined as a chest infection or "cold" with symptoms lasting for 24 hours or more, the children had contracted over this period using a parental questionnaire.
At follow up, children in the intervention group had a mean vitamin D level of 19 versus 7 ng/mL in the control group. They had also experienced significantly fewer ARIs, at 0.80 versus 0.45, an effective halving of the number of cases (rate ratio=0.52).
Further analysis adjusting for age, gender, and history of wheezing did not significantly influence the results and the risk for ARIs in the supplemented group remained 50% lower than that in the nonsupplemented group (rate ratio=0.50).
Level of serum vitamin D below or above the median at baseline also failed to significantly influence the reduction in ARI risk (rate ratio 0.41 vs 0.57), note Camargo and colleagues.
"Although our randomized controlled trial (RCT) data support a causal link, additional RCTs are needed to examine the association in other populations at increased risk of both vitamin D deficiency and ARIs," write the authors in Pediatrics.
"Future trials can examine the efficacy of different vitamin D supplementation regimens on ARI risk in general, as well as risk of ARIs caused by specific pathogens, such as respiratory syncytial virus and human rhinovirus."
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