Zinc supplementation reduces the duration of a common cold.
Article Type: Clinical report
Subject: Cold (Disease) (Care and treatment)
Zinc in the body (Usage)
Zinc in the body (Health aspects)
Dietary supplements (Usage)
Dietary supplements (Health aspects)
Author: Murphy, Kathleen
Pub Date: 09/22/2011
Publication: Name: Australian Journal of Medical Herbalism Publisher: National Herbalists Association of Australia Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2011 National Herbalists Association of Australia ISSN: 1033-8330
Issue: Date: Fall, 2011 Source Volume: 23 Source Issue: 3
Product: Product Code: 2834730 Nutrient Preparations NAICS Code: 325412 Pharmaceutical Preparation Manufacturing SIC Code: 2833 Medicinals and botanicals; 2834 Pharmaceutical preparations
Accession Number: 271323827
Full Text: Hemila H. 2011. Zinc lozenges may shorten the duration of colds: a systematic review. Open RespirMed J 5;51-8.

This systematic review aimed to examine the relationship between the total daily dose of zinc (from lozenges) and its effect on the duration of colds in patients with natural common cold infections. The Medline, Scopus and Cochrane Central Register of Controlled Trials data bases were searched for placebo controlled trials examining the effect of zinc lozenges on the duration of a common cold.

The review was restricted to trials examining the therapeutic effect of zinc lozenges on natural common cold infections. As an inclusion criterion a concurrent placebo group was required as clinically relevant common cold outcomes are largely subjective and explicitly different interventions (i.e. no placebo in one arm) might bias the comparison. Studies with adults and children were both included.

Thirteen double blind placebo controlled comparisons have examined the therapeutic effect of zinc lozenges on the duration of common cold episodes of natural origin. The total number of common cold episodes in these trials was 1407.

None of the five comparisons that used less than 75 mg/day of zinc found an effect of zinc lozenges whereas seven of the eight comparisons which used over 75 mg/day of zinc found a statistically significant benefit. In the eight high dose trials the zinc lozenges reduced the duration of colds by 32% (95% CI: 27% to 37%). All studies showed there was a significant difference between zinc and placebo.

In several trials the zinc lozenges caused acute adverse effects such as bad taste and constipation but none of the trials reported long term harm.

Even though the same dose of zinc could be used in two different lozenges, other constituents may lead to substantial differences in the levels of free zinc ions and therefore bioavailability. Four trials used 80 to 92 mg/ day and observed significant benefit. Three of these used lozenges containing zinc acetate which does not form complexes with zinc ions.

Pooling the three high dose (>75 mg/day) zinc acetate trials gives a mean effect of 42% reduction in the duration of colds. Five high dose (>75 mg/day) trials used zinc salts other than acetate. Pooling these results gave a mean effect of 20% (95% CI: 12% to 28%) reduction in the duration of colds.

This data highlights the role of zinc in acute management of the common cold notably at doses above 75 mg/day and complexed with acetate.

Kathleen Murphy MNHAA

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