Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage.
Level 1 - systematic review of randomized trials
Meta-analysis of randomized placebo-controlled trials
PubMed 28515951 · doi:10.1177/2054270417694291
What was done
A meta-analysis of randomized placebo-controlled trials evaluated the efficacy of zinc lozenges at doses over 75 mg/day for treating naturally acquired common colds. The primary outcome was common cold duration, pooled using an inverse-variance random-effects model, comparing zinc acetate versus zinc gluconate and standard versus high daily dosages.
What was found
Across seven trials with 575 participants, zinc lozenges reduced mean cold duration by 33% (95% CI: 21% to 45%). Three zinc acetate trials found a 40% duration reduction and four zinc gluconate trials found a 28% reduction; the 12 percentage point difference was not statistically significant (95% CI: -12 to +36). Five trials using 80-92 mg/day found a 33% reduction, while two trials using 192-207 mg/day found a 35% reduction, with no significant difference between dosage groups (2 percentage points, 95% CI: -29 to +32).
Why it matters
This review indicates that zinc lozenges meaningfully reduce cold duration across formulations, while showing that increasing daily zinc intake beyond approximately 100 mg/day yields no apparent additional benefit.
Limits
The total pooled sample size was modest (575 participants across 7 trials). Subgroup comparisons by zinc salt and dose tiers had very wide confidence intervals that crossed zero, limiting definitive conclusions about relative equivalence. Adverse events, tolerability, and blinding efficacy were not reported in the abstract.
Cited by
- supports Short-term high-dose zinc supplementation of about 80 mg per day lessens respiratory illness symptoms and shortens disease duration.