First, let's talk a bit about zinc. It is an essential mineral for one's health. We cannot live without it. But we don’t need very much. About 15 mgs a day will do. Zinc is important in wound healing, the functioning of our immune system, eyesight, brain development, the proper functioning of sperm and the synthesis of testosterone. (The latter might explain the traditional belief that oysters possess aphrodisiac properties due to their high zinc content). Even our senses of smell and taste depend on enzymes that include zinc in their molecular structure.
The possibility of zinc having antiviral activity was first noted in 1980 when doctors, more on a lark than anything else, treated a 3-year old girl with a 50 mg zinc gluconate tablet to try to boost her immune system because of chronic colds. She refused to swallow the tablet but did suck on it as if it were candy. Her symptoms resolved! This prompted a number of studies on the value of zinc supplements in alleviating the common cold. The trials have been split down the middle, with some showing an improvement in symptoms and some not. One study, however, published in the Annals of Internal Medicine, seemed to shift the playing field in favor of the supplements.
In a controlled trial, 50 volunteers took about 13 mg of zinc in the form of zinc acetate or placebo every 2-3 hours as long as they had cold symptoms. The results were statistically significant. The zinc group had a shorter average duration of colds, 4.5 days versus 8 days. The total zinc taken was about 80 mg a day, which although well above the daily requirement, should not cause any problems over such a short period.
Exactly how zinc works is not known. One theory is that it prevents the virus from entering cells by binding with a protein that normally facilitates such entry. Another possibility is that zinc decreases the levels of inflammatory substances in the blood called cytokines. The form of zinc supplement seems to be important. In one study, the duration of illness was significantly lower in the group receiving zinc gluconate lozenges (providing 13.3 mg zinc) but not in the group receiving zinc acetate lozenges (providing 5 or 11.5 mg zinc). None of the zinc preparations affected the severity of cold symptoms in the first 3 days of treatment. As far as the common cold is concerned, the data suggest that while zinc is not a cold cure, it may be worth a try to shorten the duration of a cold if you can get over the metallic taste and dry mouth.
Now fast forward to the 2020 coronavirus crisis. A blog post circulating on the Internet, attributed to Dr. James Robb, a pathologist who carried out some of the early work on coronaviruses back in the 197os, claims that zinc lozenges are the “silver bullet against the coronavirus.” This is not at all what Dr. Robb said in a letter that he sent privately to friends but somehow found its way into the hands of some blogger who twisted the information until it dripped nonsense all over the blogosphere.
Dr. Robb referred to research that had demonstrated an inhibition of the replication of many viruses, including coronaviruses, by exposure to zinc. He indicated that this could also be the case for the virus that causes COVID-19 disease, but pointed out that he has no experimental support for the claim. Nevertheless, he did suggest sucking on zinc lozenges several times a day if “cold-like” symptoms present. He specifically advised that this should be while lying down to give the zinc the best chance of contracting the virus.
Current evidence indicates that up to 150 mg of zinc a day over a short period does not result in zinc toxicity. While zinc lozenges are certainly no “silver bullet” the possibility that they may be of some benefit in coronavirus infection cannot be ruled out. Keep in mind, though, that there are no supporting studies.
When we speak of zinc supplements, we are not referring to metallic zinc, but to one of its salts, such as zinc gluconate, zinc acetate or zinc citrate. Sucking on pieces of metallic zinc is not the way to go. And one final point. Low levels of zinc in the blood have been associated with cognitive impairment. So maybe, by taking zinc, we will be better able to judge whether we should be taking zinc or not!