This article is more than 5 years old. Information may no longer be current.

More vitamin D may not equal fewer winter respiratory infections

Among healthy children aged 1 to 5 years, 2,000 IU of vitamin D supplementation per day compared with 400 IU supplementation did not reduce the overall incidence of upper respiratory tract infections during the winter, according research recently published in JAMA.

“Only one trial has assessed the effect of vitamin D on laboratory-confirmed upper respiratory tract infections in children specifically. It included 334 children in Japan and found a significant reduction in influenza A, but not influenza B, among children receiving 1,200 IU per day of vitamin D supplementation,” Mary Agiplay, MSc, department of pediatrics, St. Michael’s Hospital, Toronto, and colleagues wrote. “It remains unclear if vitamin D supplementation can prevent all-cause upper respiratory tract infections among children.”

The study included 349 children assigned to a high-dose vitamin D group (2,000 IU per day) and 354 children assigned to a standard-dose group (400 IU per day) for a minimum of 4 months between September and May. The standard dose is consistent with AAP guidelines for vitamin D, and the high dose is within the tolerable upper vitamin D intake suggested by the Institute of Medicine.

The NIH indicates that one cup of nonfat, reduced fat, and whole, vitamin D-fortified milk contains between 115 and 124 IU of vitamin D, and a 3-ounce can of tuna packed in water has about 154 IU of vitamin D.

The mean age of the participants was 2.7 years, and 57.7% of the participants were boys. The primary outcome was the number of laboratory-confirmed viral upper respiratory tract infections based on parent-collected nasal swabs over the winter months. Secondary outcomes included the number of influenza infections, noninfluenza infections, parent-reported upper respiratory tract illnesses, time to first upper respiratory tract infection, and serum 25-hydroxyvitamin D levels at study termination. Four children dropped out during the trial.

Researchers found that the mean number of laboratory-confirmed upper respiratory tract infections per child was 1.05 (95% CI, 0.91-1.19) for the high-dose group and 1.03 (95% CI, 0.9-1.16) for the standard-dose group, for a between-group difference of 0.02 (95%CI, –0.17 to 0.21) per child. There was no statistically significant difference in number of laboratory-confirmed infections between groups (incidence rate ratio = 0.97; 95% CI, 0.8-1.16).

In addition, there was no significant difference in the median time to the first laboratory-confirmed infection: 3.95 months (95% CI, 3.02-5.95) for the high-dose group vs. 3.29 months (95% CI, 2.66-4.14 months) for the standard-dose group, or the number of parent-reported upper respiratory tract illnesses between groups: 625 for high-dose vs. 600 for standard-dose groups (incidence rate ratio = 1.01; 95% CI, 0.88-1.16). At study termination, serum 25-hydroxyvitamin D levels were 48.7 ng/mL (95% CI, 46.9-50.5) in the high-dose group and 36.8 ng/mL (95% CI, 35.4-38.2) in the standard-dose group.

“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,” Agiplay and colleagues wrote.

“We may have just busted a myth," Jonathon L. Maguire, MD, MSc, department of pediatrics, St. Michael’s Hospital, and study co-author, said in a press release. "More [vitamin D] is not always better.” – by Janel Miller

Reference:

NIH Office of Dietary Supplements Web Page on Vitamin D.

Disclosures : Agliplay and Maguire report no relevant financial disclosures. Please see the study all other authors’ relevant financial disclosures.