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High-dose vitamin D doesn’t appear to reduce the winter sniffles for children

Toronto, July 18, 2017

By Leslie Shepherd

Dr. Jonathon Maguire
Dr. Jonathon Maguire

Giving children high doses of vitamin D doesn’t appear to reduce the winter sniffles, a new study has found.

Dr. Jonathon Maguire, a pediatrician at St. Michael’s Hospital, led a randomized clinical trial in which 350 healthy children were given a standard dose of vitamin D drops during the winter, while another 350 got a high dose.

On average, the children who received the standard dose had 1.91 colds per winter, while the children who received the high dose had 1.97 colds, which Dr. Maguire said was of no statistical difference. His findings were published online today in the journal JAMA.

“We may have just busted a myth,” said Dr. Maguire. “More is not always better. 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.”

Colds and other viruses in the upper respiratory tract (the nose and throat) are the most common infectious illnesses among children. For the past 30 years, vitamin D has been thought to play a role in preventing or reducing these infections. But Dr. Maguire said there has been little clinical trial data on which to make informed decisions.

The vitamin D Outcomes and Interventions in Toddlers (DO IT) trial was conducted to examine the effect of high-dose oral vitamin D drops (2,000 IU/day) versus the American Academy of Pediatrics recommended dose of 400IU/day on children ages 1 to 5. Each child began taking the drops between September and November of one year and continued until April or May of the following year.

The children enrolled in the clinical trial were participating in TARGet Kids!, a unique collaboration between children’s doctors and researchers from St. Michael’s Hospital and The Hospital for Sick Children in Toronto. The program follows children from birth with the aim of understanding and preventing common nutrition problems in the early years to minimize their impact on health and disease later in life.

The vitamin D study was funded by the Canadian Institutes of Health Research Institutes of Human Development, Child and Youth Health and Nutrition, Metabolism and Diabetes, and by the Thrasher Research Fund. The vitamin D drops were provided by Ddrops, the company that makes them.


This paper is an example of how St. Michael's Hospital is making Ontario Healthier, Wealthier, Smarter.

About St. Michael's Hospital

St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in more than 29 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the Hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael’s Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.