Open Access Highly Accessed Research article

Vitamin D3 and gargling for the prevention of upper respiratory tract infections: a randomized controlled trial

Emma C Goodall1, Andrea C Granados23, Kathy Luinstra3, Eleanor Pullenayegum14, Brenda L Coleman56, Mark Loeb1789 and Marek Smieja18*

Author Affiliations

1 Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada

2 Department of Medical Sciences, McMaster University, Hamilton, Ontario, Canada

3 St. Joseph’s Healthcare, Hamilton, Ontario, Canada

4 Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada

5 Department of Microbiology, Mount Sinai Hospital, Toronto, Ontario, Canada

6 School of Public Health, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada

7 Department of Medicine, Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada

8 Department of Pathology & Molecular Medicine, McMaster University, Hamilton, Ontario, Canada

9 Population Health Research Institute, McMaster University, Hamilton, Ontario, Canada

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BMC Infectious Diseases 2014, 14:273  doi:10.1186/1471-2334-14-273

Published: 19 May 2014



We undertook a 2X2 factorial, randomized controlled trial (RCT) to assess whether vitamin D3 supplementation (10,000 international units per week) versus placebo and gargling versus no gargling could prevent viral, clinical upper respiratory tract infection (URTI) in university students.


We randomized 600 students into 4 treatment arms: 1) vitamin D3 and gargling, 2) placebo and gargling, 3) vitamin D3 and no gargling, and 4) placebo and no gargling. Students completed weekly electronic surveys and submitted self-collected mid-turbinate nasal flocked swabs during September and October in 2010 or 2011. Symptomatic students also completed an electronic symptom diary. The primary and secondary outcomes were the occurrence of symptomatic clinical URTI and laboratory confirmed URTI respectively.


Of 600 participants, 471 (78.5%) completed all surveys while 43 (7.2%) completed none; 150 (25.0%) reported clinical URTI. Seventy participants (23.3%) randomized to vitamin D3 reported clinical URTI compared to 80 (26.7%) randomized to placebo (RR:0.79, CI95:0.61-1.03, p = 0.09). Eighty-five participants (28.3%) randomized to gargling reported clinical URTI compared to 65 participants (21.7%) randomized to the no gargling arm (RR:1.3, CI95:0.92-1.57, p = 0.19). Laboratory testing identified 70 infections (46.7 per 100 URTIs). Vitamin D3 treatment was associated with a significantly lower risk for laboratory confirmed URTI (RR: 0.54, CI95:0.34-0.84, p = 0.007) and with a significantly lower mean viral load measured as log10 viral copies/mL (mean difference: -0.89, CI95: -1.7, -0.06, p = 0.04). Fewer students assigned to gargling experienced laboratory confirmed URTI, however this was not statistically significant (RR:0.82, CI95:0.53-1.26, p = 0.36).


These results suggest that vitamin D3 is a promising intervention for the prevention of URTI. Vitamin D3 significantly reduced the risk of laboratory confirmed URTI and may reduce the risk of clinical infections.

Trial registration

Clinical Trials Registration: NCT01158560.

Rhinovirus; Vitamin D3; Viral load; Gargling; Randomized controlled trial; Upper respiratory tract infection