Study suggests extra vitamin D no better at preventing kids’ colds

TORONTO — Giving children high 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 last 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 that 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 IUs 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.