Zinc (Zn) is a mineral, a heavy metal micronutrient with important functions in biochemical management of immunity amongst other functions in the body. It is primarily a coenzyme that helps enzyme systems to fend off free radical damage and indirectly could ease the increased oxidative stress produced by Helicobacter pylori infection of the intestinal mucosa. It also has a role in protein and DNA synthesis, cell division, wound healing and is absolutely necessary for proper growth including sensory perception.
Its role in nutrition is well established and there is a very good internet review by the National Institutes Of Health (USA). It is associated in supplements with carnosine. The uniqueness of Zn is that, it is the second most abundant trace element in the animal body but can’t be stored, so regular dietary intake is required. The mineral when ingested in the form of lozenges does not cause ill effect or alter taste perception as once thought.
Alleviating Common Cold Symptoms With Zinc
Zinc (Zn) has long been associated with alleviating cold symptoms and has commonly been added to lozenges containing Echinacea extracts which have also been associated with reducing the effects of cold. The University of Helsinki has been regularly building up a profile on zinc in treating colds. Zinc acetate was used in medication from the 1980s. Almost, mythically, a young girl suffering leukemia had it disappear when she dissolved a therapeutic zinc tablet in her mouth rather than swallow it because of a cold she was suffering. There are about a dozen studies now which have tried to establish the efficacy of zinc lozenges but not all results are conclusive.
A meta-analysis of all the placebo-controlled trials to date assessed the whether zinc in its acetate form could ameliorate common cold infection (Hemilä, 2011). From the 13 trials that were worth assessing, five relied on zinc doses less than 75mg and in all cases the mineral had no effect. When the study used doses over 75mg there was an average reduction of 42% in the duration. Five trials used other forms of zinc rather than acetate in a daily dose over 75mg. There was an average 20% reduction in duration of the cold. Another meta-analysis found high doses of zinc acetate in lozenges shortened the duration of common-cold associated nasal discharge by 34%, nasal congestion by 37%, scratchy throat by 33%, and cough by 46% (Hemilä and Chalker, 2015).
Zinc was recently found to reduce the duration of a cold by about three days. Patients suffering a cold, 199 in total, were placed in three randomized placebo-controlled trials. They were given zinc lozenges in the study (Hemilä et al., 2016) . There was no modification of the cold symptoms due to age, sex, allergy status, smoking, symptom severity or ethnic group. The conclusion was to suggest those suffering cold could try zinc lozenges where the dose did not exceed 100 mg Zn.
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Hemilä, H. (2011) Zinc Lozenges May Shorten the Duration of Colds: A Systematic Review. The Open Respiratory Medicine J., 5 (1): 51 DOI: 10.2174/1874306401105010051
Hemilä, H., Chalker. E. (2015) The effectiveness of high dose zinc acetate lozenges on various common cold symptoms: a meta-analysis. BMC Family Practice, 16 (1) DOI: 10.1186/s12875-015-0237-6
Hemilä, H., Petrus, E.J., Fitzgerald, J.T., Prasad. A. (2016) Zinc acetate lozenges for treating the common cold: an individual patient data meta-analysis. British J. Clinical Pharmacology, DOI: 10.1111/bcp.13057