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Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage.
Meta-analysis of seven placebo-controlled zinc lozenge trials (>75 mg/day zinc) in natural colds (n=575): pooled mean common cold duration was 33% (95% CI 21%–45%) shorter with zinc; zinc acetate trials pooled to ~40% shorter duration versus ~28% for zinc gluconate trials (difference not statistically significant).
Design
- Meta-analysis of placebo-controlled zinc lozenge trials with >75 mg/day elemental zinc
- Population: 575 participants with naturally acquired common colds (7 RCTs)
Primary outcome (abstract)
- Cold duration: 33% shorter pooled mean duration in zinc arms (95% CI 21% to 45%)
- Salt subgroup: zinc acetate trials ~40% reduction vs zinc gluconate trials ~28% — difference NS (12 percentage points; 95% CI −12 to +36)
- Dose: 80–92 mg/day trials ~33% reduction; 192–207 mg/day trials ~35% — no significant dose difference in abstract
Evidence hygiene
Lozenge formulation (binders that trap free zinc ions) has historically abolished efficacy—consumer products are not interchangeable with positive trials.
Publication
Hemilä H. JRSM Open. 2017 May 2;8(5):2054270417694291. PMID 28515951; PMC5418896.
Outcomes
- Seven placebo-controlled zinc lozenge trials (>75 mg/day): pooled mean common cold duration 33% shorter with zinc vs placebo (95% CI 21% to 45%).
- Subgroup: zinc acetate trials ~40% shorter cold duration vs ~28% for zinc gluconate trials; difference between salts not statistically significant (abstract).