Zinc lozenges, as well as zinc supplements, have been the subject of several studies researching the mineral’s effectiveness in shortening the duration of cold symptoms. Results have been mixed, ranging from the lozenges having no effect on a cold to shortening a cold’s duration by one to two days.
A study from the University of Helsinki, Finland, published earlier this year added to the evidence that zinc lozenges are likely ineffective. In the study, which appeared in BMJ Open, 87 participants who contracted a cold were immediately given lozenges to use six times a day for five days. Just over half of the participants were given over-the-counter 13 milligram zinc acetate lozenges and the remainder given a placebo.
When the researchers compared results after 10 days, they found no significant difference in cold duration or easing of symptoms between each group. However, the authors say that more studies are needed before the use of zinc lozenges can be dismissed.
In lab studies, high doses of zinc can block cold viruses from adhering to the nasal lining and replicating themselves. But outside the lab, controlled studies have yielded contradictory findings. These mixed results might be due to inconsistent lozenge size and dose among studies and differences in trial length.
What you should do
If you decide to try zinc lozenges when you have a cold, start as soon as you have symptoms and follow the dosing advice on the label. Because zinc has potential side effects, such as stomach upset or a bad taste in the mouth, the lozenges shouldn’t be taken for more than a week. And don’t take them long-term in hopes of preventing colds.
This article first appeared in the July 2020 issue of UC Berkeley Health After 50.
Also see Cold or Flu? Comparing the Symptoms.