Review concludes effectiveness for zinc supplements against common cold
The results of a meta-analysis published this year in the Cochrane Database of Systematic Reviews reveal that supplementing with the mineral zinc reduces the severity of common cold symptoms as well as the length of colds. The current analysis updates a previous review, by including several new trials.
Meenu Singh and Rashmi R. Das of the Department of Pediatrics at the Post Graduate Institute of Medical Education and Research in Chandigarh, India reviewed 13 randomized, double-blinded, placebo-controlled trials that evaluated five or more days of zinc supplementation as a treatment for cold in a total of 966 participants, and two trials that tested zinc supplements as a cold preventive for at least five months among 394 participants. They concluded that zinc syrup, lozenges or tablets initiated within one day of cold symptom onset decreased the severity and length of the common cold. Additionally, a greater number of subjects were free of symptoms after one week of zinc treatment compared to subjects that received a placebo. As a preventive, five months of treatment with zinc syrup or lozenges in children resulted in 36 percent fewer colds and less time lost from school compared to those who did not use zinc.
Zinc has been shown to inhibit the rhinovirus that is primarily responsible for colds. The review's findings are significant in light of the number of people affected by colds each year and the potential for the development of complications such as ear infections, sinusitis and bronchitis.
"This review strengthens the evidence for zinc as a treatment for the common cold," Dr Singh stated. "However, at the moment, it is still difficult to make a general recommendation, because we do not know very much about the optimum dose, formulation or length of treatment."
"Our review only looked at zinc supplementation in healthy people," he noted. "But it would be interesting to find out whether zinc supplementation could help asthmatics, whose asthma symptoms tend to get worse when they catch a cold."
The virus most often responsible for the common cold is the rhinovirus. There are more than 110 different types of rhinovirus, making it impractical to figure out which one is causing any given infection (Makela MJ et al 1998). Colds can also be caused by coronaviruses, adenoviruses, coxsackieviruses, echoviruses, enteroviruses, paramyxoviruses (including several parainfluenza viruses), orthomyxoviridae (including influenza A and B), and respiratory syncytial virus (Kasper DL et al 2004).
A number of published studies show that if zinc lozenges are taken within 24 hours of the onset of common cold symptoms the severity and duration of cold miseries are significantly diminished (Hulisz D 2004; Prasad AS et al 2000; Marshall S 1998; Mossad SB et al 1996).
Rhinoviruses attach to specific cell receptor sites in sinus and throat tissues, become lodged in the nose and throat, and then replicate out of control (Gwaltney JM 2002). By binding to the same cell receptor sites as do cold viruses, zinc inhibits the ability of rhinoviruses to take hold in the body.
The key here is to dissolve two 24-mg zinc lozenges in the mouth at the very first symptom of a cold and continue doing this every 2 hours (while awake). Once rhinoviruses bind to their receptor sites in the nasal tissues and begin replicating, zinc lozenges lose their efficacy. Considering how inexpensive zinc lozenges are, it makes sense to keep them on hand so that they are immediately available if cold symptoms manifest.
One caveat to remember is that chronic use of zinc in doses over 100 mg/day may suppress immune function (Chandra RK 1984). By using two zinc lozenges every 2 hours over the course of a day, the amount of total zinc intake could easily exceed 300 mg/day. This does not appear to be a problem in the short-term. If your cold symptoms do not subside after a few days of taking zinc lozenges, it would be best to stop using them.
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