Vitamin D sources include sunlight and foods like eggs, tuna, seeds, etc. During winter, our vitamin D levels tend to lessen due to less sunlight. This is also the time when there's a rise in the number of common cold cases. The study compared the effect of high- and standard-dose of vitamin D on the risk of children catching a cold or flu in winter.
The researchers randomly assigned children aged one through five years to receive 2,000 IU/d of vitamin D oral supplementation (high-dose group; n=349) or 400 IU/d (standard-dose group; n=354) for a minimum of four months between September and May. The results of the average number of infections for high-dose and the standard-dose groups respectively were 1.05 and 1.03 respectively.
"These findings do not support the routine use of high-dose vitamin D supplementation in children for the prevention of viral upper respiratory tract infections," stated the study.
The study doesn't challenge the usefulness of the recommended vitamin D dosage, but suggests that high dosage may not be better for colds. A limitation of the study could be that children may have had upper respiratory tract infections without swabs being submitted.
The study was published in the Journal of the American Medical Association (JAMA)