TUESDAY, July 18, 2017 (HealthDay News) -- When it comes to vitamin supplements, more is not always better, according to a new study that found even high doses of vitamin D don't protect children from colds in the winter.
"We may have just busted a myth," said study leader Dr. Jonathon Maguire.
"Our findings do not support the routine use of high-dose vitamin D supplementation for the prevention of wintertime upper respiratory tract infections among healthy children," added Maguire. He is a pediatrician at St. Michael's Hospital in Toronto.
Vitamin D is often called the "sunshine" vitamin, because human skin manufactures the nutrient upon contact with sunlight. It's also found in certain foods, such as fatty fish. But many people now take a daily vitamin D supplement, as well.
For the past 30 years, it's been thought that vitamin D can help prevent or reduce the severity of colds and other respiratory tract infections in children, Maguire noted. But there's been little clinical trial data to help doctors and parents make informed decisions, he said.
So how effective is this supplement for children? To find out, the researchers had 350 healthy toddlers take the standard dose of vitamin D drops -- 400 IU/day -- as recommended by the American Academy of Pediatrics for children aged 1 to 5.
Another group of 350 healthy children received a high dose (2,000 IU/day) of the vitamin.
The youngsters began taking the vitamin D drops in the fall of one year and continued taking them until spring of the following year.
Children who took the standard dose had an average of 1.91 colds over the winter, compared with 1.97 colds among the children who received the high dose, the findings showed.
That difference is not statistically significant, Maguire said in a hospital news release.
Two pediatricians who reviewed the study had slightly different opinions on the findings, however.
Dr. Peter Richel agreed with the conclusions of the study. "Though the use of high-dose vitamin D is not harmful, I have never seen any conclusive evidence that it makes any difference in the management of upper respiratory infections -- more commonly known as colds -- in patients of any age," he said. Richel directs pediatrics at Northern Westchester Hospital in Mount Kisco, N.Y.
"In fact, I have often said that by giving patients high doses of vitamin D, we are simply making 'expensive urine,' " since the nutrient passes through the system, Richel added.
But Dr. Michael Grosso, chair of pediatrics at Huntington Hospital in Huntington, N.Y., believes vitamin D supplementation might still have value.
While the study's conclusions are "scientifically correct," he cautioned that "the study does not prove that there is no effect of vitamin D for reducing upper respiratory infections. Children with underlying health problems were not evaluated. Children of other ages were not included. Other dosing regimens were not compared."
For his part, Richel believes there is a simple and time-tested way to help prevent colds in kids.
"It is important to teach children -- and adults -- the importance of good hand hygiene, which is the most effective method of prevention," he said.
The findings were published online July 18 in the Journal of the American Medical Association.
The Harvard School of Public Health has more on vitamin D.