Taking high-doses of vitamin D supplements does not appear to reduce the risk of catching the common cold among young children, according to Canadian researchers.
Among children one to five years of age, a daily high-dose of vitamin D did not reduce overall wintertime upper respiratory tract infections, according to a study published in the Journal of the American Medical Association.
“We may have just busted a myth. More is not always better”
Viral upper respiratory tract infections are the most common infectious illnesses of childhood, noted the study authors from the University of Toronto.
Both observational and clinical trial data have suggested a link between low levels of serum 25-hydroxyvitamin D and increased rates of respiratory tract infections, they said.
However, they said that whether winter supplementation of vitamin D reduced the risk among children was previously unknown.
Dr Jonathon Maguire and colleagues randomly assigned 700 children aged one to five to receive either 2,000 IU/d of vitamin D oral supplementation or 400 IU/d.
Each child began taking the drops between September and November of one year and continued until April or May of the following year – taking them for a minimum of four months.
The average number of confirmed upper respiratory tract infections per child were 1.05 for the high-dose group and 1.03 for the standard-dose group.
There was also no significant difference in the median time to the first laboratory-confirmed infection – 3.95 months for the high-dose group versus 3.29 months for the standard-dose group.
High-dose vitamin D ‘does not cut cold risk in young children’
Likewise, there was no difference for the number of parent-reported upper respiratory tract illnesses between groups – 625 for high-dose versus 600 for standard-dose groups.
“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,” said the study authors.
Dr Maguire added: “We may have just busted a myth. More is not always better.”
The authors acknowledged that a potential limitation of the study was that children may have had upper respiratory tract infections without swabs being submitted.