Effect of vitamin D3 supplementation on upper respiratory tract infections in
healthy adults: the VIDARIS randomized controlled trial.
Author(s): Murdoch DR, Slow S, Chambers ST, Jennings LC, Stewart AW, Priest PC, Florkowski
CM, Livesey JH, Camargo CA, Scragg R.
Affiliation(s): Department of Pathology, University of Otago, Christchurch, PO Box 4345,
Christchurch 8011, New Zealand. david.murdoch@otago.ac.nz
Publication date & source: 2012, JAMA. , 308(13):1333-9
CONTEXT: Observational studies have reported an inverse association between serum
25-hydroxyvitamin D (25-OHD) levels and incidence of upper respiratory tract
infections (URTIs). However, results of clinical trials of vitamin D
supplementation have been inconclusive.
OBJECTIVE: To determine the effect of vitamin D supplementation on incidence and
severity of URTIs in healthy adults.
DESIGN, SETTING, AND PARTICIPANTS: Randomized, double-blind, placebo-controlled
trial conducted among 322 healthy adults between February 2010 and November 2011
in Christchurch, New Zealand.
INTERVENTION: Participants were randomly assigned to receive an initial dose of
200,000 IU oral vitamin D3, then 200,000 IU 1 month later, then 100,000 IU
monthly (n = 161), or placebo administered in an identical dosing regimen (n =
161), for a total of 18 months.
MAIN OUTCOME MEASURES: The primary end point was number of URTI episodes.
Secondary end points were duration of URTI episodes, severity of URTI episodes,
and number of days of missed work due to URTI episodes.
RESULTS: The mean baseline 25-OHD level of participants was 29 (SD, 9) ng/mL.
Vitamin D supplementation resulted in an increase in serum 25-OHD levels that was
maintained at greater than 48 ng/mL throughout the study. There were 593 URTI
episodes in the vitamin D group and 611 in the placebo group, with no
statistically significant differences in the number of URTIs per participant
(mean, 3.7 per person in the vitamin D group and 3.8 per person in the placebo
group; risk ratio, 0.97; 95% CI, 0.85-1.11), number of days of missed work as a
result of URTIs (mean, 0.76 days in each group; risk ratio, 1.03; 95% CI,
0.81-1.30), duration of symptoms per episode (mean, 12 days in each group; risk
ratio, 0.96; 95% CI, 0.73-1.25), or severity of URTI episodes. These findings
remained unchanged when the analysis was repeated by season and by baseline
25-OHD levels.
CONCLUSION: In this trial, monthly administration of 100,000 IU of vitamin D did
not reduce the incidence or severity of URTIs in healthy adults.
TRIAL REGISTRATION: anzctr.org.au Identifier: ACTRN12609000486224.
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