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Given the current pandemic, “the search for potential [preventive] and therapeutic antiviral strategies is of particular and urgent interest.” So, what about zinc, which is known in some cases to have antiviral and anti-inflammatory benefits? I looked into it as a potential treatment after the fact-checking site Snopes validated that a noted virologist did indeed make a recommendation back in February to “Stock up now with zinc lozenges.” He based his supposition on the efficacy of zinc for common colds, up to 29 percent of which are caused by coronaviruses.
There’s actually a sweet backstory to that: a three-year-old girl undergoing chemotherapy for leukemia (a disease marked by low zinc levels) refused to swallow a zinc supplement. Immunosuppressed, she had just started getting a cold. Instead of swallowing the supplement, she just let it dissolve in her mouth and the cold seemed to disappear within hours. Okay, cute little anecdote, but this observation led her father—her own father—to conduct the ﬁrst randomized double-blind placebo-controlled trial on zinc lozenges for the common cold.
That’s how it all started/ But there have since been more than a dozen randomized controlled trials published, and, overall, researchers have found that zinc is indeed beneficial in reducing both duration and severity of the common cold when taken within the first twenty-four hours of symptom onset. Zinc lozenges…appear to shorten colds, by about three days…with significant reductions…in nasal discharge and congestion and hoarseness, and cough.
The common cold results for zinc are often described as “mixed,” but that appears to be because some studies used zinc lozenges containing added ingredients like citric acid that strongly sequester zinc; so, little or no free zinc is actually released. They taste better, but what’s the point if you don’t actually get the zinc?
So, what’s the best way to take zinc for the common cold? Lozenges containing around 10 to 15 milligrams of zinc taken every two waking hours for a few days, starting immediately upon symptom onset, as either zinc acetate or zinc gluconate without zinc binders such as citric acid, tartaric acid, glycine, sorbitol, or mannitol may work best. Best…for the common cold, but what about for COVID-19?
There are a number of purported mechanisms for the potential protection afforded by zinc. The first is that it interferes with the attachment of rhinoviruses, the most common cause of the common cold, to our cells. This presumably wouldn’t help us in the case of COVID-19, since our new coronavirus utilizes a different docking receptor.
Zinc also appears to slow rhinovirus replication, at least in a petri dish. What about coronaviruses? Zinc inhibits the coronavirus that causes SARS, by interfering with the virus’s ability to replicate its genetic code, but that was in conjunction with a chemical that ferried zinc inside the cells. There are natural dietary compounds that may play a similar function, but even if viral replication were able to be slowed in your throat where the lozenge is, what we care about most is stopping replication of the COVID-19 virus in the lungs.
But a third mechanism by which zinc may help seems more promising: boosting our antiviral immunity. For example, giving zinc pills to children with severe regular pneumonia has been shown to be effective in reducing mortality as much as three-fold over placebo. Three times higher death rates in the sugar pill group. But these studies were done in countries like Uganda, India…, and Ecuador, where there may have been pre-existing zinc deficiencies. So yeah, taking zinc if you’re zinc deficient; no wonder that helps, but it’s unclear if similar benefits could be had in higher-income countries with better population-wide micronutrient status.
Some have suggested that despite the lack of clinical data—no one has yet put zinc to the test for COVID-19—maybe it could help. I’m skeptical it would be helpful in well-nourished individuals, but, if taken as directed, it shouldn’t hurt, though zinc supplements and lozenges can cause nausea, especially when taken on an empty stomach, and some other gastrointestinal symptoms. And one should never put zinc in their nose. In the drug store you’ll find all sorts of intranasal zinc gels, sprays, and swabs that have been linked to the potentially permanent loss of one’s sense of smell.
(Oh, and happy ending: That three-year-old girl beat the cancer, never relapsed, and grew up to become a scientist herself.)
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