Researchers bust vitamin D myth
Kids given high doses get just as many viruses as those given standard amounts
Giving children high TORONTO daily doses of vitamin D instead of the standard recommended amount doesn’t appear to reduce the number of times they come down with wintertime sniffles, a study suggests.
For the past 30 years, vitamin D has been thought to play a role in preventing or reducing the number of colds and bouts of flu children experience over the fall and winter.
But Toronto researchers found children who received the standard daily dose of 400 international units (IUs) and those given 2,000 IUs per day both had an average of almost two upper respiratory infections during the cold-weather months.
“What we found was there was no difference in the number of viral infections that children got, regardless of which group they were in — the high-dose group or the regular-dose group,” said Dr. Jonathon Maguire, a pediatrician at St. Michael’s Hospital.
“I think that we just busted a myth here, that giving more vitamin D doesn’t seem to protect against viral infections.”
To conduct the study, published Tuesday in the Journal of the American Medical Association, researchers enrolled about 700 children aged one to five, whose parents were to administer one of two daily oral doses of vitamin D. Half of the kids were randomly selected to receive 400 IUs, while the other half were to get 2,000 IUs.
Maguire said data from laboratory experiments had suggested vitamin D might help produce certain proteins that can protect the respiratory system from viral infections.
“So we hypothesized that if we gave children a high dose of vitamin D, we might promote the production of these proteins and protect them from getting wintertime colds,” he said.
“But what this paper is showing is that giving more has no benefit in terms of viral infections.”
Among the group of children who received 400 I Us of vitamin D drops daily, each developed 1.91 colds on average, compared to 1.97 each in the group of kids given 2,000 IUs — a difference that Maguire called not statistically significant.
“We asked parents every time the child got a cold to take a (swab) of the nasal secretions and send them back to us,” he said.
“We ran that sample on a fancy machine that told us exactly what virus they had. So we knew whether they had an adenovirus or a coronavirus or enterovirus or influenza.
“There really was no difference between the groups, they were almost identical,” said Maguire, adding that the number of flu cases in the high-dose group was slightly lower.
The researchers confirmed the children had received their assigned dosages through tests that measured the level of vitamin D in their blood, both at the start and end of the study. As well, parents were asked to return their used vials