While zinc lozenges may offer some adults relief from cold symptoms, they do nothing for childhood sniffles, a study published recently shows.
Researchers found that a group of Cleveland-area public school children taking zinc lozenges or an inactive tablet within a day of coming down with a cold all took about the same amount of time - nine days - to shed their congestion, sore throats and hoarseness.Writing in The Journal of the American Medical Association, longtime zinc researcher Dr. Michael Macknin of the Cleveland Clinic Foundation in Ohio and colleagues also said there was no significant difference between the two groups in the time it took any of nine cold symptoms to disappear.
Macknin's team also investigated whether zinc lozenges helped adults who had colds. Five of the studies showed benefit and five didn't. All the trials used different doses or formulations of zinc, however.
The latest study was the first devoted to children. Nearly 250 students from two suburban school districts were randomly assigned to take five or six 10 milligram zinc gluconate glycine lozenges or placebo tablets.
Even though the researchers tried to make real and inactive lozenges as similar as possible, nearly twice as many zinc-takers reported bad-taste reactions or nausea, and one-third were more likely to experience mouth, tongue or throat discomfort.
"The discrepant results between these studies in adults and the current study in children may be explained by different dosages or flavoring of the formulations, the ages of the subjects, the time of year when the studies were performed (the viruses may have been different than in successful adult trials) or chance differences between the placebo and zinc groups," the researchers said.
The study was funded by the Quigley Corp. of Doylestown, Pa., which makes zinc lozenges and in which Macknin holds 20,000 shares of stock.
Common colds are one of the most frequent illnesses in the world, with more than 200 viruses known to cause the illness in adults. American adults have an average of two to four colds each year, children have an average of six to eight colds.
No one knows exactly what effect zinc has on cold viruses, although it's believed the substance interferes with their ability to replicate.
Macknin and his associates conclude that still more studies of zinc lozenges are needed among different age groups, dosages and formulations to define "what role, if any, zinc has in the treatment of common cold symptoms."
In an accompanying editorial, Dr. Anne Gadomski of Bassett Hospital in Cooperstown, N.Y., wrote that the latest study "by no means closes the door on zinc gluconate lozenges. Rather, it opens the field to more studies among children in different geographic locales, with more varied socioeconomic and dietary risk factors" and during times when other cold viruses are present.