Zinc & Respiratory Tract Infections
Zinc for the prevention or treatment of acute viral respiratory tract infections in adults
a rapid systematic review and meta-analysis of randomized controlled trials
Acute viral respiratory tract infections (RTIs) are ubiquitous in the community. Clinical presentations range from milder cold and influenza-like illnesses to more serious conditions such as viral pneumonia and severe acute respiratory syndrome.
Infection rates vary according to a viral pathogen, location, season, and the host’s health status and age. Although most infections are self-limiting, the high incidence leads to substantial healthcare costs and broader economic impacts from school and work absenteeism. Except for influenza and SARS-CoV-2 vaccinations, prophylactic and therapeutic options are limited. Clinical practice guidelines focus on hand hygiene, reducing inappropriate antibiotic use, and symptomatic relief with over-the-counter medications. Some guidelines recommend zinc.
However, systematic reviews of zinc are limited by variations in administration route or formulation, are outdated, have been withdrawn or are low quality. The mechanisms for how zinc might work include broad-spectrum antiviral properties in vitro against most of the common respiratory viruses, including coronaviruses.
Zinc is important for immunity, inflammation, hemostasis, ACE 2 activity and assists with tissue responses to hypoxia. Not surprisingly then, zinc has garnered attention during the global COVID-19 pandemic. Both high-income and low-income countries have seen increased zinc supplement use and sales. Some healthcare workers, clinicians, and hospitals are already using zinc to prevent or treat SARS-CoV-2 infections.
In response to calls for rapid evidence appraisals to inform self-care and clinical practice during the COVID-19 pandemic, we developed a rapid systematic review protocol to evaluate zinc for the prevention and treatment of SARS-CoV-2 and other viral RTIs. At the time of this review, results from COVID-19 randomized controlled trials (RCTs) were all pending. Therefore, this rapid review updates previous systematic reviews of RCTs investigating any type of zinc intervention to prevent or treat viral RTIs in adult populations.
Is zinc more than a dietary supplement?
The role of zinc in viral RTIs appears to extend beyond supplementing nutritional intake to prevent or treat zinc deficiency. The two RCTs that used prophylactic oral zinc excluded zinc deficiency prior to enrolment. While none of the other RCTs excluded deficiency, the risk was low as participants were generally healthy and the three RCTs conducted in China all used a low dose intranasal zinc spray (1.15 mg daily) that is unlikely to have substantial systemic effects. The rationale for topical intranasal and sublingual zinc is based on the in vitro effects of zinc ions that can inhibit viral replication, stabilise cell membranes and reduce mucosal inflammation. However, other mechanisms may also be at play, at least for sublingual and oral administration as activation of T lymphocytes, monocytes and granulocytes have been observed in healthy young adult males within 24–48 hours of taking 15 mg of oral zinc daily.
In adult populations in which zinc deficiency is unlikely, our review found when zinc was used for prophylaxis, there was a lower risk of contracting a clinical illness consistent with a community-acquired viral RTI, but not following direct HRV inoculation.
When used for treatment, zinc was found to shorten the duration of symptoms and reduce day 3 symptomatic severity, but not overall daily symptom severity. While there was an increased risk of non-serious AEs that may limit tolerability for some, the risk of serious AEs was low. Limitations to the GRADE certainty/quality assessments of the available evidence included high RoB and/or small sample sizes in primary studies, and considerable heterogeneity in the duration effect estimates. We were unable to answer questions about the comparative efficacy, effectiveness, and acceptability of different zinc formulations and doses, and their mechanisms of action. Prior to recommending zinc, patient preferences, financial and opportunity costs, and availability of different zinc interventions should be considered. Clarification of the efficacy and mechanism of zinc in viral respiratory infections, including SARS-CoV-2 infections, warrants further research.
Πηγή Άρθρου / Story Source
A meta-Analysis «Zinc for the prevention or treatment of acute viral respiratory tract infections in adults: a rapid systematic review and meta-analysis of randomized controlled trials» BMJ Open.2021 Nov 2 doi: 10.1136/BMJ open-2020-047474. https://pubmed.ncbi.nlm.nih.gov/34728441/