Zinc is no COVID-19 magic bullet, but it has shown to help with other coronaviruses.

Calling the specific virus that is causing COVID-19 “coronavirus” is a bit like calling the Ford Explorer “the SUV.” Both statements are true, but with both, one is part of the other. There are lots of different SUVs; there are lots of different coronaviruses.

Many common colds are caused by coronaviruses. Various scientific studies (we’ll get to those in a moment) have shown zinc lozenges to be effective in shortening the misery phase of common colds. So in the face of a coronavirus pandemic, here’s a big question many are asking: can zinc shorten the duration of – or even diminish the symptom load and thereby lessen the impact – of COVID-19?

The answer is we don’t know yet. But to twist the analogy: if changing the oil helps a Jeep Grand Cherokee avoid the shop, it’s a good bet that doing the same will benefit the Ford Explorer, too.

Dr. Ian Tullberg bears no responsibility for the above comparison. But as far as helping patients get over colds, “there’s good evidence that oral zinc works well,” the medical director of UCHealth Medical Group Urgent Care said.

With respect to the specific coronavirus that is causing the pandemic now, “the problem is that this is still so early that we don’t have the knowledge if it works or not,” Tullberg said. “However, zinc is something that will not hurt you, and there may be some benefit.”

Those who swear by zinc as a cold remedy know to take it when they first start to feel a scratchy throat. They try to hit it early – right when the cold’s coming on. Research spanning decades has shown that using zinc lozenges through the course of the cold does make a difference.

The data around Zinc and coronaviruses

Four different coronaviruses cause perhaps as many as a quarter of all common colds.

A study published in 1996 shuffled 100 Cleveland Clinic employees who self-reported catching colds into two groups. Fifty took lozenges containing 13.3 milligrams of zinc gluconate – the dosage of today’s Cold-Eeze and other over-the-counter lozenges – every two hours as long as they had cold symptoms. Fifty others took placebo lozenges. The study was double-blind, so neither patients nor researchers knew which patients had the placebo. The findings: the zinc group cleared symptoms more than three days earlier – 4.4 days versus 7.6 days of the placebo group, and, until that point, suffered fewer days with cough, headache, hoarseness, nasal congestion, and sore throat (fever, muscle aches, scratchy throat and sneezing remained similar during the cold’s duration). Zinc has side effects – “bad-taste reactions” (understandable) and, among 20 percent of those taking zinc, nausea.

More recent zinc-common-cold studies have been mixed. A team led by Finnish researcher Harri Hemilä reviewed three previous zinc trials and, in a report published in 2016, found that those taking zinc shortened their colds by nearly three days. When the same group ran their own trial, though, they found no difference in cold symptoms or duration, according to a study published in January 2020.

A 2010 study led by University of Leiden Medical researchers in the Netherlands sought to understand how zinc inhibited replication of a cousin of SARS-CoV-2: SARS-CoV, the original SARS of the 2003 outbreak. Click through for details, which get into the biochemical nitty-gritty, but the gist is that zinc throws a wrench in the virus’s RNA-synthesis machine.

Now, there are caveats with zinc. First, like everything else, there can be too much of a good thing – more than 150 milligrams a day for adult. That’s about 11 lozenges; the recommended zinc-lozenge maximum for adults being six and just four for children ages 12-17 (research has shown younger children to not benefit from taking zinc). Second, zinc nasal sprays shouldn’t be used, Tullberg says. In 2009, the U.S. Food and Drug Administration warned against such products because people who used them lost their sense of smell.

What does that background say about the effectiveness of zinc and the SARS-CoV-2 now known as coronavirus? It is, at best, effectiveness by association. But an email that recently went viral as a blog post indicates that Tullberg is in good company with his openness to zinc lozenges as a way to at least try and mitigate COVID-19 flu symptoms.

A virologist’s take on Zinc and COVID-19

The email was one that James A. Robb sent to friends and family. He is University of Colorado School of Medicine MD, a pathologist, and molecular virologist who, while at the University of California, San Diego in the 1970s, did pioneering work in understanding coronaviruses. He wrote:

For all updates and to read more articles about the new coronavirus, please visit uchealth.org/covid19

Stock up now with zinc lozenges. These lozenges have been proven to be effective in blocking coronavirus (and most other viruses) from multiplying in your throat and nasopharynx. Use as directed several times each day when you begin to feel ANY “cold-like” symptoms beginning. It is best to lie down and let the lozenge dissolve in the back of your throat and nasopharynx. Cold-Eeze lozenges is one brand available, but there are other brands available.

Snopes.com, a website dedicated to debunking (or confirming) internet myths, investigated after his words were twisted by others and reposted with exaggerated claims such as zinc being a “silver bullet” against coronavirus. In an email to Snopes, Robb confirmed that he’d written the above and added, “In my experience as a virologist and pathologist, zinc will inhibit the replication of many viruses, including coronaviruses. I expect COVID-19 will be inhibited similarly, but I have no direct experimental support for this claim. I must add, however, that using zinc lozenges as directed by the manufacturer is no guarantee against being infected by the virus, even if it inhibits the viral replication in the nasopharynx.”

In short, if coronavirus is like an SUV, zinc lozenges may well be something like an oil change, though we’ll need many more miles to really know for sure.

(This story has been updated to remove reference to a retracted 2013 Cochrane Review article on zinc’s effect on the common cold and add references to the 2016 and 2020 Finnish-led studies on zinc and the common cold.)