Zinc for the Common Cold | Vol. 4 / No. 9.4

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One of the many, many parts of the human rhinovirus | Photo: Energy.gov, CC0 (public domain)

Is there any hope for taking zinc lozenges (like zicam) to treat the common cold? A new retraction seems at first to say maybe not, but the reasons for the retraction suggest all hope may not be lost.

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I received a bunch of “cold remedies” in my stocking this Christmas, and posted a photo on facebook because that’s what you do if you’re an aging millennial. But a friend of mine suggested that said remedies were entirely placebo. I, of course, responded with a study that suggested zinc might shorten the duration of colds. I did not, unfortunately for my research cred, notice that it had been withdrawn until today.

“JAMA article on zinc for the common cold retracted,” reads the headline in my inbox (<unapologetic endorsement>I get Retraction Watch e-mails and you should too</unapologetic endorsement>). Not only had the article I cited to my friend, a Cochrane Review meta-analysis, been withdrawn last year, but so had another, more recent article in JAMA. Both articles were by the same pair of researchers, Rashmi Ranjan Das of the All India Institute of Medical Sciences and Meenu Singh of PGIMER, Chandigarh, and seem to have been based on the same research.

Unfortunately, there were problems with that research. Harri Hemilä, of the Department of Public Health at the University of Helsinki, had published his own review of the research concerning zinc and the common cold back in 2011 in the Open Respiratory Medical Journal, and pointed out that some of the work was misattributed and borderline plagiarized, and others were “sloppy.”

Thankfully for fans of shorter colds, Hemilä’s own meta-review still stands, and high doses of zinc do indeed still seem to shorten the duration of colds:

Thirteen placebo-controlled comparisons have examined the therapeutic effect of zinc lozenges on common cold episodes of natural origin. Five of the trials used a total daily zinc dose of less than 75 mg and uniformly found no effect. Three trials used zinc acetate in daily doses of over 75 mg, the pooled result indicating a 42% reduction in the duration of colds (95% CI: 35% to 48%). Five trials used zinc salts other than acetate in daily doses of over 75 mg, the pooled result indicating a 20% reduction in the duration of colds (95% CI: 12% to 28%).

This study shows strong evidence that the zinc lozenge effect on common cold duration is heterogeneous so that benefit is observed with high doses of zinc but not with low doses. The effects of zinc lozenges should be further studied to determine the optimal lozenge compositions and treatment strategies.

You can find more on the story over at Retraction Watch.

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Richard Ford Burley is a human, writer, and doctoral candidate at Boston College, as well as Deputy Managing Editor at Ledger, the first academic journal devoted to Bitcoin and other cryptocurrencies. In his spare time he writes about science, skepticism, feminism, and futurism here at This Week In Tomorrow.