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Zinc supplementation for upper respiratory infections (common cold)

Oral zinc (often lozenges) has been randomised versus placebo for preventing and treating colds; the 2024 Cochrane update finds uncertain prevention effects but suggests treated colds may be shorter on average while carrying more non-serious adverse events than placebo.

Scope

Zinc supplementation for URI / common cold means zinc-only arms versus placebo in randomised trials—excluded by the linked Cochrane protocol when zinc is bundled with other minerals/vitamins/herbs (read labels before pooling consumer products).

Evidence anchors (PubMed)

  • Zinc acetate IPD meta (treatment trials): Hemilä et al. 2016 (Br J Clin Pharmacol; PMID 27378206; hemila-2016-zinc-acetate-lozenges-common-cold-ipd-meta-bcp) pooled individual patient data from three double-blind RCTs (n = 199 cold patients)—one-stage meta-analysis estimated mean 2.73 days shorter illness (95% CI 1.8–3.3) versus placebo lozenges; read formulation caveats alongside the broader Cochrane update below.
  • Cochrane review update: Nault et al. 2024 (Cochrane Database Syst Rev; PMID 38719213; nault-2024-zinc-common-cold-cochrane) — 34 RCTs (n = 8,526); prevention: pooled RR 0.93 (95% CI 0.85–1.01; low-certainty). Treatment: pooled mean duration MD −2.37 days (95% CI −4.21 to −0.53; low-certainty; high I²); non-serious adverse events higher with treatment zinc (RR 1.34, 95% CI 1.15–1.55; moderate-certainty).

Distinct protocols

  • Vitamin C (vitamin-c-supplementation) — parallel historical cold literature with different subgroup winners.
  • Probiotic supplementation (probiotic-supplementation) — gut-targeted IBS evidence, not oropharyngeal zinc kinetics.

Safety / formulation hygiene

Intranasal zinc histories include anosmia case reports—oral lozenge trials dominate modern safety discussion; still read dose, salt form, and metal taste/nausea adverse-event tables.

Evidence