Sunday, June 20, 2021

What is the Efficacy of Zinc in Preventing the Common Cold?

Summary

  • The common cold can cause many unwanted symptoms such as muscle aches, headache, and congestion. Each year this virus is the reason for countless doctors’ visits and missed days at work and school. There are many over-the-counter (OTC) products to choose from when it comes to cold relief.
  • Many OTC products contain zinc, which has been used for a long time to shorten cold symptom duration and severity.
  • Zinc may work by inhibiting the cold virus from binding to nasal membranes as well as replicating.
  • To answer this inquiry, we will look at a systemic review that analyzes studies for the prevention of the common cold, as well as UpToDate direction on preventing the common cold in adults.

Clinical Data

The systemic review that we will use to answer this inquiry searched through CENTRAL, MEDLINE, EMBASE, CINAHL, Web of Science, LILACS, WHO ICTRP and clinicaltrials.gov to create their study [1]. For their selection criteria of studies within these databases, they chose randomized, double-blind, placebo-controlled trials that used zinc for at least five consecutive days or at least five months to prevent the common cold. The review included 16 therapeutic trials involving 1,387 participants as well as two preventative trials that include 394 participants. One randomized control trial the review used from 1984 showed that zinc shortened the duration of cold symptoms by roughly seven days [2]. For this shortened duration of symptoms, patients had to begin zinc therapy of one 23mg zinc lozenge every other hour while awake and start no later than 72 hours after cold symptoms developed. The overall results of the study showed that zinc was statistically significant in reducing the duration of cold symptoms however did not significantly impact the severity of symptoms. The review also revealed that adverse effects due to zinc are higher in groups treated with zinc vs placebo. Also to consider is the type of lozenge (flavored, unsweetened, etc.) as well as how long the patient can dissolve and absorb the zinc from the lozenge. This can affect the bioavailability of zinc and reduce or increase its efficacy. Of further note [3], zinc is not suggested in the treatment of the common cold due to uncertain benefits but known adverse effects. The FDA also has issued a public health advisory advising zinc-containing intranasal products not to be used due to reports of permanent anosmia.

Overall zinc has been shown in trials to be effective in preventing the common cold, however, the evidence is inconclusive and further studies are needed. Zinc is not currently recommended for the treatment of the common cold, and intranasal zinc products should especially be avoided.

Resources

  1. Singh M, Das RR. Zinc for the common cold. Cochrane Database Syst Rev. 2013;(6):CD001364. Published 2013 Jun 18. doi:10.1002/14651858.CD001364.pub4
  2. Eby GA, Davis DR, Halcomb WW. Reduction in duration of common colds by zinc gluconate lozenges in a double-blind study. Antimicrob Agents Chemother. 1984;25(1):20-24. doi:10.1128/aac.25.1.20
  3. The Common Cold in Adults: Treatment and Prevention. In: UpToDate, Post, TW (Ed), UpToDate, Waltham, MA, 2021.

 

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