Vitamin D and Respiratory Tract Infections: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
What this study found
Vitamin D supplementation reduced the risk of respiratory tract infections overall, with an OR of 0.64 (95% CI, 0.49 to 0.84; p = 0.0014). Daily dosing appeared more protective than bolus dosing, with OR 0.51 (95% CI, 0.39 to 0.67) versus OR 0.86 (95% CI, 0.62 to 1.20). Heterogeneity was substantial (Cochran's Q = 35.7, p < 0.0001, I2 = 72%). Reported adverse events and serious adverse events were not considered related to the study drug.
- Study & population
- Systematic review and meta-analysis of 11 randomized controlled trials involving 5660 participants.
- Intervention
- Oral vitamin D supplementation, primarily cholecalciferol (vitamin D3), was evaluated across regimens including 1600 IU/day daily dosing and several large bolus schedules such as 100,000 IU every 4 weeks, 100,000 IU as a single dose, 100,000 IU every 3 months, and 200,000 IU initially followed by 200,000 IU after 1…
- Key limitation
- The evidence was limited by substantial between-study heterogeneity, different dosing regimens, and broad variation in participant age and health status.
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Open PDFOriginal abstract
Background Low levels of 25-OH vitamin D are associated with respiratory tract infection (RTI). However, results from randomized controlled trials are inconclusive. Therefore, we performed a systematic review and meta-analysis to assess the preventive effect of vitamin D supplementation on RTI. Methods Randomized, controlled trials of vitamin D for prevention of RTI were used for the analysis. The risks of within-trial and publication bias were assessed. Odds ratios of RTI were pooled using a random-effects model. Heterogeneity was assessed using Cochran's Q and I2. Meta-regressions and subgroup analyses were used to assess the influence of various factors on trial outcome. The pre-defined review protocol was registered at the PROSPERO international prospective register of systematic reviews, registration number CRD42013003530. Findings Of 1137 citations retrieved, 11 placebo-controlled studies of 5660 patients were included in the meta-analysis. Overall, vitamin D showed a protective effect against RTI (OR, 0.64; 95% CI, 0.49 to 0.84). There was significant heterogeneity among studies (Cohran's Q p<0.0001, I2 = 72%). The protective effect was larger in studies using once-daily dosing compared to bolus doses (OR = 0.51 vs OR = 0.86, p = 0.01). There was some evidence that results may have been influenced by publication bias. Interpretation Results indicate that vitamin D has a protective effect against RTI, and dosing once-daily seems most effective. Due to heterogeneity of included studies and possible publication bias in the field, these results should be interpreted with caution.