New research suggests that zinc may shorten cold symptoms by about two days, but conclusive evidence is lacking and side effects are a concern. More standardized studies are needed to fully understand the effectiveness of zinc.
A recent Cochrane review found that zinc supplementation can shorten the duration of cold symptoms by about two days.
A recent Cochrane review suggests that zinc supplementation may reduce the duration of cold symptoms by about 2 days. However, the results are not conclusive and the possible benefits must be weighed against potential side effects.
Since the 1980s, zinc products have been sold as cold treatments and are particularly popular in the United States. Zinc is an essential mineral found naturally in many foods and plays a role in immune function. Most people in high-income countries get enough zinc through their diet, but zinc deficiency can occur as we age and with some chronic diseases.
Mechanism and research
The theory behind zinc-based lozenges, sprays, and syrups is that zinc can interfere with virus replication when it comes into contact with virus particles in the nose, mouth, and throat. Zinc has been shown to inhibit viral replication in petri dishes and mice, but this alone doesn’t tell us whether it would have any effect in real people.
To find out whether zinc can help prevent or treat the common cold, the researchers looked at 19 human trials that investigated zinc as a treatment and 15 as a preventive measure. They found a lot of variation between studies in how zinc was administered, how much it was administered, how a “cold” was defined, and what was measured.
Eight studies with 972 participants investigated zinc as a treatment to shorten the duration of colds. Together, the results of these studies provide low-certainty evidence that it may help shorten the duration by about two days, compared to the average one-week duration in the group given a placebo.
Effects and side effects of cold prevention
This review did not find strong evidence to conclude that zinc treatment affects the severity of cold symptoms. Prevention studies have not shown clear evidence that taking zinc before the onset of a cold is beneficial. People who took preventive zinc had similar results to those who didn’t.
Common side effects of zinc reported in trials included intestinal upset, nausea, and an unpleasant taste. There was no clear evidence of more serious side effects directly attributable to zinc.
“Those considering zinc for the treatment of colds should be aware of the limited evidence base and possible side effects,” said Darryl Nault of the Maryland College of Integrative Medicine, lead author of the review. says the assistant professor. “Ultimately, it’s up to the individual to decide whether the risk of potentially unpleasant side effects is worth the benefit of saving a few days off their illness. Consult your doctor if you feel unwell.” However, the best advice is to let your doctor know if you are taking supplements.There have been many trials investigating zinc, but the approaches vary so it is difficult to draw any firm conclusions. .”
The studies included in the review varied in many ways, including the type of zinc, the amount of zinc administered, whether it was administered as a lozenge or nasal spray, and how results were reported and measured. Some trials measured over a fixed time frame and asked participants if they still had a cold at the end. Some researchers measured the time from onset of symptoms to resolution, but the definition varied slightly between studies. Few studies monitored the status of individual symptoms such as sore throat, cough, and fever, and there was insufficient evidence to draw reliable conclusions about specific symptoms.
“The evidence for zinc is still inconclusive and more research is needed to be confident in its effectiveness,” says Susan Wieland, an assistant professor at the university. University of Maryland School of Medicine, senior author of the review. “Future studies should adopt standardized methods for delivering and reporting treatments and defining and reporting outcomes. Focusing on the most promising zinc product types and doses, and using appropriate statistical methods. Additional studies evaluating its use and outcomes that are important to patients will help us understand whether zinc can be used to treat the common cold.”
Reference: “Zinc for Preventing and Treating the Common Cold” by Daryl Nault, Taryn A Machingo, Andrea G Shipper, Daniel A Antiporta, Candyce Hamel, Sahar Nourouzpour, Menelaos Konstantinidis, Erica Phillips, Elizabeth A Lipski, L Susan Wieland, 9 May 2024 Cochrane Database of Systematic Reviews.
DOI: 10.1002/14651858.CD014914.pub2
The study was funded by the National Centre for Complementary and Integrative Health.
