Effect of moderate or high versus low dose daily vitamin D on COVID-19 incidence: A double-blind, parallel-group randomized clinical trial.
Clin NutrJul 4, 2026 (epub)
David O Meltzer, James N Moy, Andrew W Schram et al.
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In 30 seconds
This double-blind, parallel-group randomized trial evaluated the impact of moderate (4000 IU/day) or high (10,000 IU/day) versus low (400 IU/day) vitamin D doses on COVID-19 incidence among 955 participants. The study found no significant reduction in COVID-19 risk with moderate or high doses compared to low doses, with a risk of 10.9% versus 14.7%, respectively (aHR:0.73; P=0.10).
Key findings
- COVID-19 risk was 10.9% for moderate/high doses versus 14.7% for low dose (aHR:0.73; P=0.10).
- Moderate dose showed a lower risk compared to low dose (aHR:0.62; P=0.045).
- High dose did not significantly reduce COVID-19 risk compared to low dose (aHR:0.99; P=0.98).
- Among seroconverting participants, no significant difference in COVID-19 incidence was observed (aOR:0.62; P=0.25).
Why it matters
Understanding the role of vitamin D in COVID-19 risk is crucial for developing effective prevention strategies. This study suggests that higher doses may not confer additional protection, informing clinical decisions regarding supplementation.