The average duration and severity of a common cold may be reduced by sucking zinc lozenges, say the authors of a US trial, but the blindness of their trial has been questioned.
Researchers from the University health centre, Detroit, Michigan, undertook a randomised, placebo-controlled trial of the efficacy of zinc acetate lozenges in 50 volunteers suffering from a cold (Annals of Internal Medicine 2000;133:245).
In the group taking zinc, the average duration of symptoms was 3.5 days shorter and severity scores were half those of volunteers in the placebo group. "We found that treatment with zinc lozenges was associated with a decrease in the average duration and severity of the common cold," the authors say.
Dr Norman Desbiens (University of Tennessee college of medicine) says that the effect of zinc is still questionable (ibid, p302). He says that the placebo and zinc lozenges used in the new trial may not have tasted the same and, therefore, the trial may not have been adequately blinded. He suggests that study of the molecular basis of the effectiveness of zinc should continue.