Zinc in Treating Childhood Common Colds

August 1998; Volume 1: 94-95

Sources: Macknin ML, et al. Zinc gluconate lozenges for treating the common cold in children: A randomized controlled trial. JAMA 1998;279:1962-1967. Gadomski A. A cure for the common cold? Zinc again. JAMA 1998; 279:1999-2000.

To determine the efficacy of zinc gluconate glycine (ZGG) treatment of colds in children and adults, researchers enrolled 249 students in grades 1-12 within the first 24 hours of experiencing at least two of nine symptoms of the common cold. The students were randomized to ZGG 10 mg orally dissolved five times daily (grades 1-6) or six times daily (grades 7-12) or placebo.

Time to resolution of all cold symptoms did not differ significantly between students receiving ZGG (n = 124) and those receiving placebo (n = 125) (median, 9 days for both). There were no significant differences in the time to resolution of any of the nine symptoms studied. Compared with controls, more students in the zinc group reported adverse effects (88.6% vs 79.8%; P = 0.06), including bad taste (60.2% vs 37.9%; P = 0.001); nausea (29.3% vs 16.1%; P = 0.01); mouth, tongue, or throat discomfort (36.6% vs 24.2%; P = 0.03); and diarrhea (10.6% vs 4.0%; P = 0.05).

In this community-based, randomized, double-masked, placebo-controlled trial, researchers found that ZGG lozenges were not effective in treating cold symptoms in children and adolescents.

COMMENT

These investigators from the Cleveland Clinic Foundation were brave. There have been no previously reported randomized, controlled studies in children. Their study was funded by the Quigley Corporation, makers of ZGG (Cold-Eeze) lozenges. The primary investigator owns 20,000 shares of the corporation. A previous study Dr. Macknin participated in and published in the Annals of Internal Medicine showed positive results for Cold-Eeze in adults.

This time, however, the shoe is on the other foot-these negative results have been condemned as "bad science" by Quigley. In fact, the science is very good. The design assured that the two-sided, type I error rate would not exceed 0.05; 95% confidence intervals were used for the estimates of median time to resolution; analyses were independently verified by two biostatisticians. Virologic testing, serologic assays, and objective measures of cold severity would raise the science to an even higher level, as the authors note.

Symptoms of cough, headache, hoarseness, muscle ache, nasal congestion, nasal drainage, scratchy throat and sore throat, and sneezing were self-reported, just as they are in practice.

Placebos contained calcium lactate pentahydrate instead of zinc and were formulated to be as "identical as possible in appearance, flavoring content, and texture"-important in zinc, since it must be taken so often, and tastes so bad, even when coated in corn syrup and sucrose, as it was here.

How might zinc work? It "prevents the formation of viral capsid proteins, may induce the production of interferon, and inhibits human prostaglandin metabolism." In fact, as Dr Gadomski writes in an editorial, zinc supplementation of 10-20 mg daily in children growing up in developing countries improves growth response and reduces diarrheal disease.

Conclusion

As previously noted for adults (see Alt Med Alert 1998;1:36), zinc cannot currently be recommended to reduce cold symptoms in children. There is no evidence to support regular supplementation during cold season, as aggressive marketing on many packages suggests.