Zinc for colds: lozenges versus daily tablets
If zinc helps a cold, the evidence is about lozenges used early, not about a daily tablet taken for months. An individual-patient meta-analysis of zinc acetate lozenges found shorter colds when the lozenges were the treatment. Long high-dose zinc can upset the stomach and can interfere with copper. Do not turn a five-day lozenge study into a permanent high dose.
Cold-season marketing treats every zinc bottle as the same intervention. The lozenge trials are narrower than that.
The lozenge evidence
Hemilä and colleagues pooled individual patient data from zinc acetate lozenge trials and reported shorter colds (PMID 27378206). The lozenges were started when symptoms started. A zinc gluconate or bisglycinate tablet swallowed with breakfast is not that intervention. Zinc bisglycinate is a form question about tolerability and absorption, not a cold cure.
Dose and duration
The lozenge trials used a high short course, well above a standard daily allowance. Nausea and a bad taste are common. Weeks of high-dose zinc are how people develop copper deficiency and neurologic symptoms. When the cold is over, stop. Children, pregnancy, and anyone on chronic zinc should follow a clinician rather than a lozenge label.
Sources
- Hemilä H, et al. Zinc acetate lozenges for treating the common cold: an individual patient data meta-analysis. Br J Clin Pharmacol. 2016. PMID: 27378206.