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High doses of zinc lozenges may shorten cold duration
Hemilä H. Open Respir Med J. 2011;5:51-58.
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The effect of zinc lozenges on the duration of the common cold is heterogeneous, suggesting that the beneficial effect is only observed with daily doses of more than 75 mg of zinc, according to new findings published in The Open Respiratory Medicine Journal.
Previous research has examined the therapeutic effect of zinc lozenges on common cold episodes of natural origin. However, the findings have varied, according to background information in the study. For this reason, Harri Hemilä, MD, PhD,of the University of Helsinki in Finland, examined whether the total daily dose of zinc correlates with the variation in results.
Hemilä searched placebo-controlled trials examining the effect of zinc lozenges on common cold duration from the Medline, Scopus and Cochrane Central Register of Controlled Trials databases, and pooled data of the identified trials.
Of the 13 trials identified, no effect was observed among the five trials that used a less than 75-mg daily dose of zinc. Conversely, a 42% reduction in the duration of the common cold was observed in three trials that used a more than 75-mg daily dose of zinc ascetate (95% CI, 35-48); and a 20% reduction in five trials that used a more than 75-mg daily dose of zinc as salt form (95% CI, 12-28).
“This meta-analysis shows that a large part of the divergence can be explained by the variation in the total daily dose of zinc that the person obtained from the lozenges,” Hemilä wrote in the study. “No effect of zinc lozenges was seen in trials where the total daily dose of zinc was less than 75 mg, whereas the majority of trials with higher zinc doses did find benefit.”
“A 20% to 40% decrease in the duration of colds in several independent placebo-controlled, double blinded, randomized trials with an inexpensive and safe method implies that the method should be taken into practical use, although we may hope for further research,” Hemilä told Infectious Disease News. “However, many of the commercially available lozenges have either low dose of zinc or constituents that bind zinc, such as citrate, and therefore, simply taking some kind of zinc lozenges does not guarantee an effect against the common cold.” – by Ashley DeNyse
Disclosure: Dr. Hemilä reports no relevant financial disclosures.
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