People have been searching for a cure for the common cold for centuries. To date, there is nothing that actually overcomes cold viruses the way antibiotics conquer bacteria. However, for years scientists have been evaluating reports that zinc might soothe symptoms and speed healing. Studies have confirmed that adequate zinc is essential for good antiviral immune response (Advances in Nutrition, July 1, 2019). A new meta-analysis offers support to the idea of taking zinc for the common cold (BMJ Open, Nov. 2. 2021).
Evidence on Zinc for the Common Cold:
Researchers have been interested in the possible effectiveness of zinc for preventing or treating SARS-CoV-2. Consequently, an international team of investigators reviewed the medical research on this topic. Although trials of zinc against COVID-19 are in process, the results have not yet been published.
However, the scientists analyzed 28 randomized controlled trials covering more than 5,000 participants. The studies tested a variety of zinc formulations and doses against common respiratory tract infections, mostly colds. People who took zinc as a preventative were less likely to come down with sniffles and sneezes. Zinc tablets or nasal spray prevented about five colds (or other infections) per 100 person-months. The number needed to treat was 20, which is quite respectable.
According to the reviewers, taking zinc under the tongue or as a nasal spray once symptoms began shortened illness duration by about two days. That is certainly not a dramatic improvement, but many people might welcome that. These studies revealed no serious adverse reactions, though zinc can cause nausea, vomiting and irritation of the mouth or nose.
How Much Zinc for the Common Cold?
For at least a decade, researchers have said they don’t have enough data to recommend a dosing regimen. Unfortunately, that is still true. The studies in the meta-analysis employed different doses and formulations but did not test them against each other. In our experience, zinc for the common cold works best if taken within 24 hours of the first symptoms.
A Sniff of Zinc:
Although many people are enthusiastic about zinc-based nasal sprays, we worry about a potential loss of the sense of smell. Back in 2009, the FDA warned people against using one of the most popular brands, Zicam. We received a question right around that time.
Q. A friend of mine took Zicam for a cold last fall and the next day woke to find she had completely lost her sense of smell. It has not returned.
Her sense of taste was also compromised and she has to overseason her food now to taste it. Do you have any suggestions?
A. We don’t know of any treatments to restore the sense of smell. The FDA has warned consumers not to use certain Zicam products (Cold Remedy Nasal Gel, Cold Remedy Nasal Swabs, and kids size Nasal Swabs). At that point, the agency had received more than 130 reports of loss of the sense of smell associated with these zinc-containing nasal products. Unfortunately, in certain cases this reaction seems to be irreversible.