NEW YORK (Reuters Health) – Adding to the growing body of conflicting evidence, the results of a new study indicate that the use of intranasal zinc gluconate does not prevent or treat the common cold. The report appears in the December 1st issue of Clinical Infectious Diseases.
Dr. Ronald B. Turner from the University of Virginia Health System, Charlottesville, randomly assigned 41 volunteers to treatment with zinc gluconate and 50 volunteers to placebo. Patients were inoculated with rhinovirus after being treated for 3 days. After inoculation with rhinovirus, the subjects were treated for 6 more days.
Thirty-seven patients (74%) who received placebo developed rhinovirus infection, as did 32 of the subjects (78%) treated with zinc gluconate, Dr. Turner found. Treatment with zinc gluconate had no effect on total symptom score, rhinorrhea, nasal obstruction, or the proportion of subjects who developed clinical colds, he adds.
Why the outcomes of studies of zinc and the common cold are inconsistent remains a mystery, Dr. Turner notes. Some previous studies that did not show a benefit from zinc have been criticized for using inappropriate formulations (see Reuters Health report August 3). The studies were faulted for using zinc formulations with "inadequate zinc ion availability," Dr. Turner said.
Dr. Turner points out that this notion of "zinc ion availability" has not been tested directly. "Furthermore, studies that have used identical zinc products have produced dramatically different results," he adds.
Dr. Turner concludes that "these data do not support a role for intranasal zinc gluconate for prevention or treatment of the common cold. It seems unlikely that the role of zinc in the common cold will be resolved by additional clinical trials. If additional studies of zinc treatment of the common cold are to be done, they might be more productively directed at testing specific hypotheses for a proposed mechanism of action."