Does high-dose vitamin D reduce the incidence of wintertime upper respiratory infections in otherwise healthy children?

Daily administration of high-dose vitamin D (2000 IU) did not reduce the incidence of wintertime upper respiratory infections (URIs) compared with standard dose vitamin D (400 IU) in otherwise healthy children residing in Toronto, Canada. (LOE = 1b)

Aglipay M, Birken CS, Parkin PC, et al, for the TARGet Kids! Collaboration. Effect of high-dose vs standard-dose wintertime vitamin D supplementation on viral upper respiratory tract infections in young healthy children. JAMA 2017;318(3):245-255.  [PMID:28719693]

Randomized controlled trial (double-blinded)

Foundation

Concealed

Outpatient (primary care)

Vitamin D increases the synthesis of antimicrobial peptides in respiratory epithelium and may thus reduce viral replication and subsequent URIs. These investigators enrolled 703 healthy children, 1 year to 5 years old, who presented for a scheduled well-child visit prior to the wintertime viral season in Toronto, Ontario, Canada. Eligible children randomly received (concealed allocation assignment) liquid vitamin D in a standard dose (400 IU daily) or a high-dose (2000 IU daily). Drops were identical in taste, volume, and color. Throughout the winter months parents completed a symptom checklist and collected viral nasal swabs for suspected URIs. The individuals who assessed outcomes remained masked to treatment group assignment. Follow-up occurred for 99.4% of participants for approximately 6 months (winter lasts a LONG time up there). Mean baseline serum 25-hydroxyvitamin D levels were comparable in the standard-dose and high-dose groups (36.9 ng/mL and 35.9 ng/mL, respectively). Using intention-to-treat analysis, no significant differences occurred between the 2 groups in the mean number of infections per child based on both parent-reported URIs and laboratory confirmed upper respiratory virus infections from nasal smears. There was a statistically significant difference in serum 25-hydroxyvitamin D levels between the standard-dose and high-dose groups after treatment (36.8 ng/mL vs 48.7 ng/mL, respectively). The study was 90% powered to detect a reduction of at least 1 URI per winter season between the 2 treatment groups.