In a new study from Western Sydney University, researchers found a zinc supplement might help stave off the symptoms of respiratory tract infections, such as coughing, congestion, and sore throat, and cut illness duration.
Respiratory tract infections include colds, flu, sinusitis, pneumonia and COVID-19. Most infections clear up by themselves, but not all.
And they often prove costly in terms of their impact on health services and time is taken in sick leave.
Zinc has a key role in immunity, inflammation, tissue injury, blood pressure and in tissue responses to lack of oxygen.
As a result, it has generated considerable interest during the current pandemic for the possible prevention and treatment of COVID-19 infection.
In the study, the team evaluated zinc for the prevention and treatment of SARS-CoV-2, the virus responsible for COVID-19, and other viral respiratory tract infections.
The review includes 28 clinical trials involving 5446 adults, published in 17 English and Chinese research databases up to August 2020. None of the trials specifically looked at the use of zinc for the prevention or treatment of COVID-19.
The most common zinc formulations used were lozenges followed by nasal sprays and gels containing either zinc acetate or gluconate salts.
Doses varied substantially, depending on the formulation and whether zinc was used for prevention or treatment.
The team found that compared with a dummy treatment (placebo), zinc lozenges or nasal spray prevented 5 respiratory tract infections in 100 people a month.
These effects were strongest for curbing the risk of developing more severe symptoms, such as fever and influenza-like illnesses.
On average, symptoms cleared up 2 days earlier with the use of either a zinc spray or liquid formulation taken under the tongue (sublingual) than when a placebo was used.
During the first week of illness, participants who used sublingual or nasal spray zinc were nearly twice as likely to recover as those who used placebo: 19 more adults out of 100 were likely to still have symptoms a week later if they didn’t use zinc supplements.
While zinc wasn’t linked to an easing in average daily symptom severity, it was linked to a clinically significant reduction in symptom severity on day 3.
Side effects, including nausea and mouth/nose irritation, were around 40% more likely among those using zinc, but no serious side effects were reported in the 25 trials that monitored them.
The team says zinc is a viable ‘natural’ alternative for the self-management of non-specific respiratory tract infections.
And how exactly zinc might exert its therapeutic effects on respiratory infections, including COVID-19, warrants further research.
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The study is published in BMJ Open. One author of the study is Jennifer Hunter.