Vitamin D supplementation reduced the risk of experiencing at least 1 acute respiratory tract infection, and daily or weekly vitamin D supplementation without additional bolus doses protected against acute respiratory tract infection, according to a study published in BMJ.
Adrian R Martineau, PhD, from the Queen Mary University of London, and colleagues identified 532 unique studies to determine whether vitamin D supplementation can decrease the risk of acute respiratory tract infection. Data sources included Medline, Embase, the Cochrane Central Register of Controlled Trials, Web of Science, Clinicaltrials.gov, and the International Standard Randomized Controlled Trials Number registry from inception to December 31, 2015. Placebo-controlled trials of supplementation with vitamin D3 or vitamin D2 of any duration were eligible for inclusion if data on incidence of acute respiratory tract infection were collected prospectively and pre-specified as an efficacy outcome.
Individual participant data (IPD) was requested for age, sex, cluster identifier, racial or ethnic origin, influenza vaccination status, history of asthma, history of chronic obstructive pulmonary disease (COPD), body weight, height, serum 25-hydroxyvitamin D concentration, study allocation (vitamin D vs placebo), and details of any stratification or minimization variables.
Subgroups were defined according to baseline vitamin D status (serum 25-hydroxyvitamin D <25 vs ≥25 nmol/L), vitamin D dosing regimen (daily or weekly without bolus dosing vs a regimen of at least 1 bolus dose of at least 30,000 IU vitamin D), dose size (800-1000 IU), age (1-65 years), body mass index (<25 vs ≥25), and presence compared with absence of asthma, COPD, and previous influenza vaccination.
Of the 532 studies that were assessed for eligibility, 25 with a total of 11,321 randomly assigned participants fulfilled the eligibility criteria. IPD were sought and obtained for all 25. Outcome data for the primary analysis of participants experiencing at least 1 acute respiratory tract infection were obtained for 10,933 (96.6%) participants.
Vitamin D supplementation reduced the risk of acute respiratory tract infection among all participants experiencing at least 1 acute respiratory tract infection (odds ratio [OR], 0.88). In subgroup analysis, protective effects were seen in those receiving daily or weekly vitamin D without additional bolus doses (OR, 0.81), but not in those receiving 1 or more bolus doses (OR, 0.97).
Protective effects were stronger in those with baseline 25-hydroxyvitamin D levels <25 nmol/L (OR, 0.30) than in those with baseline 25-hydroxyvitamin D levels ≥25 nmol/L (OR, 0.75).
“Our study records a major new indication for vitamin D supplementation: the prevention of acute respiratory tract infection,” said the authors. “We also show that people who are very deficient in vitamin D and those receiving daily or weekly supplementation without additional bolus doses experienced particular benefit.”
- Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 15 February 2017. doi: 10.1136/bmj.i6583