There’s no proof that zinc lozenges, which are marketed for relieving symptoms of the common cold, work as advertised, according to a new research review.
Zinc nasal gels, on the other hand, show some promise for aiding stuffy, runny noses, researchers found.
The review, published in the Sept. 1 issue of journal Clinical Infectious Diseases, included 14 clinical trials where participants were randomly assigned to take zinc — as a lozenge, nasal spray or nasal gel — or a placebo.
Half of the studies found that zinc limited cold symptoms compared with the placebo, while half found no benefits.
However, of those 14 trials, only four met the predetermined quality-control criteria the review authors laid out. Among those four trials, three found no benefits from zinc lozenges or nasal spray.
The one positive study tested a zinc nasal gel, which proved to lessen cold symptoms and shorten the duration of cold sufferers’ misery.
Still, that’s not enough to recommend the use of the zinc nasal gel, said senior study author Dr. Jack M. Gwaltney, Jr., at the University of Virginia School of Medicine in Charlottesville.
“It’s just one study,” he said.
When it comes to zinc lozenges, Gwaltney believes the verdict is in.
“There has been sufficient study of the zinc lozenges that, to me, shows they simply don’t work,” he said.
Zinc is a mineral that plays an important role in many bodily functions, including immune system activity. Lab studies have suggested that zinc ions can keep cold virus cells from multiplying. But, as the current review highlights, it’s not clear that this translates into fewer cold symptoms.
On a biological basis, zinc nasal gels make more sense than lozenges, according to Gwaltney, since “the virus is growing in your nose.” But additional, well-designed trials are still needed to prove they work, he said.