Zinc helps to stave off respiratory infection symptoms and cut illness duration
A zinc supplement may help alleviate the symptoms of respiratory tract infections, such as coughing, congestion, and sore throat, as well as shorten the duration of the disease, according to a pooled analysis of the available evidence published in the open access journal BMJ Open.
However, the researchers note that the quality of the evidence on which these findings are based is diverse, and it is unclear what an optimal formulation or amount of this nutrient would be.
Colds, flu, sinusitis, pneumonia, and COVID-19 are all examples of respiratory tract infections. Most infections resolve on their own, but not all. And they are frequently costly in terms of the impact on health services and the time spent on sick leave.
Zinc has an important part in immunity, inflammation, tissue injury, blood pressure, and tissue responses to oxygen deprivation.
As a result, during the current pandemic, there has been a lot of interest in the possible prevention and treatment of COVID-19 infection.
The researchers investigated zinc for the prevention and treatment of SARS-CoV-2, the virus responsible for COVID-19, and other viral respiratory tract illnesses in response to calls for quick evidence evaluations to influence self-care and clinical practise.
Because the results of numerous relevant clinical studies were not yet available when that review was released, this present review brings the available data up to date.
The evaluation contains 28 clinical studies including 5446 adults, which were published in 17 English and Chinese research databases between August 2020 and August 2021. None of the trials particularly looked at the use of zinc for COVID-19 prevention or treatment.
Lozenges were the most commonly used zinc formulation, followed by nasal sprays and gels containing zinc acetate or gluconate salts. Doses differed significantly depending on the formulation and whether zinc was used for prophylaxis or treatment.
A pooled analysis of the data of 25 trials found that zinc lozenges or nasal spray, when compared to a dummy treatment (placebo), avoided 5 respiratory tract infections in 100 persons each month.
These effects were strongest when it came to lowering the likelihood of acquiring more serious symptoms, such as fever and influenza-like diseases. This, however, is based on only three investigations.
When either a zinc spray or a liquid formulation taken under the tongue (sublingual) was utilised, symptoms cleared up 2 days faster than when a placebo was used.
Participants who used sublingual or nasal spray zinc were nearly twice as likely to recover as those who used placebo throughout the first week of illness: 19 more persons out of 100 were expected to still have symptoms a week later if they didn't use zinc supplements.
While zinc was not linked to a reduction in average daily symptom severity, it was linked to a clinically meaningful reduction in symptom severity on day 3.
Side effects, such as nausea and mouth/nose irritation, were roughly 40% more prevalent in zinc users, but no significant side effects were observed in the 25 trials that tracked them.
However, sublingual zinc did not diminish the chance of getting an infection or cold symptoms following human rhinovirus injection, and there were no differences in illness duration between individuals who utilised zinc supplements and those who did not.
The comparative efficiency of various zinc compositions and dosages was also unclear. Furthermore, the included studies differed greatly in terms of quality, size, and design.
According to the researchers, "the marginal advantages, strain specificity, drug resistance, and potential hazards of other over-the-counter and prescription drugs make zinc a plausible 'natural' alternative for the self-management of non-specific [respiratory tract infections]."
"[Zinc] also provides clinicians with a management choice for patients who are desperate for speedier recovery timelines and may seek an unwarranted antibiotic prescription," they continue.
"However, clinicians and consumers should be aware that considerable uncertainty exists regarding the clinical efficacy of different zinc formulations, doses, and administration routes, as well as the extent to which efficacy may be influenced by the ever-changing epidemiology of the viruses that cause [respiratory tract infections]," they warn.
They suggest that more research is needed to determine how zinc might exercise its therapeutic effects on respiratory infections, especially COVID-19.