Generality
Generalities on Zinc
Zinc is a mineral that is essential for human health and is widely used for therapeutic purposes, for example for the treatment of the common cold.
In addition to structuring human proteins, this metal is necessary for enzymatic functioning and many other compounds.
Zinc has been known for many years for its antiviral effect against rhinoviruses - cold viruses - found above all in the laboratory.
Zinc is normally taken with food but it is possible to increase its intake through supplements. These have a different effect depending on the therapeutic goal. For the treatment of colds, zinc - or rather its ionic derivatives - are administered in tablets to be sucked and dissolved in the oral cavity.
Research on the effect of zinc on colds began in 1984 and continues today. The differences in the experimental results, which we will analyze later, may be due in part to the differences in the constituents of the tablets.
Action Mechanism
How does zinc work for colds?
We know that human rhinovirus - the most common human viral pathogen - is the statistically predominant cause of the common cold. It is hypothesized that the mechanism of action by which zinc can reduce the severity and / or duration of cold symptoms includes:
- Suppression of nasal inflammation
- Direct inhibition of the bond between the rhinovirus and the receptor
- Inhibition of rhinovirus replication in the nasal mucosa.
Note : the pharmaceutical forms used for zinc-based supplements are the tablets to be sucked.
Effectiveness
Scientific studies on the effectiveness of zinc for colds
A systematic review in 2012 suggested that "zinc formulations can shorten the duration of common cold symptoms"; however, further research was needed to investigate possible side effects.
The 2013 Cochrane review found that zinc supplementation at doses above 75 mg / day within 24 hours of the onset of cold symptoms can reduce the average duration of symptoms by 1 day. He also found that individuals undergoing zinc supplementation were less likely to have symptoms longer than 7 days after the onset of the disease.
A meta-analysis of 2015 found no difference on the symptoms of patients suffering from common cold treated with acetate type zinc. Although these "candies" work by increasing the concentration of zinc in the oral cavity, continuing to increase concentration would not result in a proportional improvement in efficacy. In general, in this study, the duration of nasal secretion was reduced by 34%, nasal congestion by 37%, sneezing by 22%, throat irritation by 33%, sore throat by 18%, hoarseness of 43% and cough of 46%. Zinc tablets reduced the duration of muscle pain by 54%, but there was no significant effect on the duration of headache and fever.
A meta-analysis of 2016 on the zinc-acetate for the treatment of the common cold found that - compared to an average duration of 7 days - the symptomatology was found to be shorter than 2.7 days.
A work of 2017 on the zinc-acetate tablets showed that, regardless of age, sex, race, allergy, smoking and severity, these can favor the remission of the symptoms of the common cold faster - 70% vs 27% - than normal - ratio of 3: 1.
The meta-analysis of 2017 compared high-dose zinc-acetate tablets (> 75 mg / day of elemental zinc) with zinc gluconate tablets and found no difference in efficacy. Furthermore, there was no significant evidence that zinc doses> 100 mg / day are more effective than those equal to 80-92 mg / day.
However, due to the lack of data, there is insufficient evidence to determine whether the preventive use of zinc-based supplements can reduce the likelihood of contracting the common cold. Furthermore, the effects of zinc supplementation on the duration and severity of cold symptoms in people with AIDS / HIV or chronic disease are not known, due to the lack of highly specific studies.
Side effects
Side effects of zinc for colds: is it safe?
In some studies, cold zinc tablets caused acute adverse effects, such as unpleasant taste, but none of the investigations reported long-term damage. Furthermore, many of the adverse effects, particularly as regards taste, may be caused by the specific composition of the candies to be sucked - see excipients - and probably do not reflect the impact of the zinc ions contained in them. For example, zinc gluconate with dextrose (glucose) worsens from a taste point of view only a few weeks after manufacture; those based on zinc dihydrate acetate instead, in mixture with dextrose 1: 100, should not have this complication. Tests carried out on the side effects of zinc acetate - daily dose of 92 mg of mineral - did not show significant differences with the placebo.
There have been several cases of people who have suffered from loss of smell using zinc-based nasal sprays. In 2009 the "US Food and Drug Administration" specified that people should not use nasal sprays containing zinc.
Bibliography
- Zinc - Fact Sheet for Health Professionals - Office of Dietary Supplements, US National Institutes of Health. February 11, 2016. Retrieved January 7, 2018
- Singh M, Das RR (June 2013) - Zinc for the common cold - The Cochrane Database of Systematic Reviews (6): CD001364
- Common Cold and Runny Nose - United States Centers for Disease Control and Prevention. September 26, 2017. Retrieved January 7, 2018
- Hemila, H. (2017) - Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage - Journal of the Royal Society of Medicine open. 8: 2054270417694291
- Hemila, H .; Fitzgerald, J .; Petrus, E .; Prasad, A. (2017) - Zinc Acetate Lozenges May Improve the Recovery Rate of Common Cold Patients: An Individual Patient Data Meta-Analysis - Open Forum Infect Diseases. 4: ofx059
- Hemila, H .; Petrus, E .; Fitzgerald, J .; Prasad, A. (2016) - Zinc acetate lozenges for treating the common cold: an individual patient data meta-analysis - British Journal of Clinical Pharmacology. 82: 1393–1398
- Hemila, H .; Chalker, L. (2015) - The effectiveness of high dose zinc acetate lozenges on various common cold symptoms: a meta-analysis - BMC Family Practice. 16: 24
- Science, M .; Johnstone, J .; Roth, DE; Guyatt, G .; Loeb, M. (2012) - Zinc for the treatment of the common cold: A systematic review and meta-analysis of randomized controlled trials - Canadian Medical Association Journal. 184 (10): E551–61
- Eby, George A. (2010) - Zinc lozenges as a cure for the common cold - A review and hypothesis - Medical Hypotheses. 74 (3): 482–92
- Prasad, Ananda S .; Beck, Frances WJ; Bao, Bin; Snell, Diane; Fitzgerald, James T. (2008) - Duration and Severity of Symptoms and Levels of Plasma Interleukin-1 Receptor Antagonist, Soluble Tumor Necrosis Factor Receptor, and Adhesion Molecules in Patients with Common Cold Treated with Zinc Acetate - The Journal of Infectious Diseases. 197 (6): 795–802
- Zinc for Colds: Lozenges & Nasal Sprays - WebMD. Retrieved October 25, 2013.
- Zinc can cut length of common cold - NHS Choices. May 8, 2012.
