#394 Vitamin D and Respiratory Tract Infections: Does the sun’s vitamin chase the cold?
CLINICAL QUESTION
Does Vitamin D supplementation prevent acute respiratory tract infections?
BOTTOM LINE
Vitamin D supplementation does not decrease the risk of developing respiratory tract infections, regardless of vitamin D level or age. This is supported by several large randomized controlled trials (RCTs).
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EVIDENCE
- Results statistically significant unless indicated.
- Four systematic reviews of RCTs, past 5 years.1-4 Most comprehensive (various doses, follow-up 7 weeks-5 years):4
- Proportion of participants with ≥1 respiratory infection: 4
- 49% (vitamin D) versus 50% (placebo): not statistically different (40 RCTs, 61,589 participants). 4
- Largest five RCTs (>1000 events each): No difference.4
- No effect regardless of baseline vitamin D levels, examples:4
- Baseline vitamin D <25nmol/L: 73.3% (vitamin D) versus 73.6% (placebo): Not statistically different.
- Baseline vitamin D >75nmol/L: 25% both groups.
- Sub-group analyses sometimes show positive effects.
- Limitations: Risk of spurious results due to multiple comparisons, publication bias (results skewed by small positive trials), improbable results (example: Vitamin D doses 400-1000IU would have benefits but doses 1000-2000IU would not),4 inconsistency within and across systematic reviews (example: subgroup ages 1-15 shows possible benefit but meta-regression analysis does not;4 other review shows no benefit for age group 1-18).1
- Adverse events: 4
- Serious: 6.9% versus 7.3%: no difference.
- Renal stones: 2% both groups.
- Other systematic reviews similar.1-3
CONTEXT
- Subgroup analyses suggest patients with low vitamin D levels get more respiratory infections; however since supplementation does not improve outcomes, this suggests low vitamin D level is likely a surrogate marker for poor health.4
- Cows milk in Canada is fortified with Vitamin D.5
- Guideline (based on low certainty evidence) indicates that supplementation may prevent respiratory infections in children, 6 but accompanying systematic review did not find a significant difference (12 RCTs, 12,951 children aged 1-18).1
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It is good to know that Vitamin D does not reduce respiratory infections.
Even though Vit D supplementation does not reduce respiratory infections, at least there are no adverse effects such as increased risk of renal stones.