The effect of zinc acetate lozenges was not modified by age, sex, race, allergy, smoking, or baseline common cold severity. Therefore, the 3-day reduction in common cold duration may be widely applicable.
The dose of zinc in the three studies was between 80 to 92 mg/day. Such doses are substantially higher than the recommended daily zinc intake in the USA, which is 11 mg/day for men and 8 mg/day for women. However, in other controlled studies, zinc has been administered in doses of 100 to 150 mg/day to certain patient groups for months with few adverse effects. Therefore, it seems highly unlikely that 80-92 mg/day of zinc for one to two weeks, starting very soon after the onset of the first cold symptoms, might lead to long-term adverse effects.
Even though there is strong evidence that properly formulated zinc acetate lozenges can shorten the duration of common cold by up to 3 days, many zinc lozenges on the market appear to have either too low doses of zinc or they contain substances that bind zinc ions, such as citric acid. Therefore, the findings of this study should not be directly extrapolated to the wide variety of zinc lozenges on the current market.
Although Dr. Harri Hemilä from the University of Helsinki suggests that the optimal formulation of zinc lozenges and the best frequency of their administration should be further investigated, he also instructs common cold patients to test individually whether zinc lozenges are helpful for them.
"Given the strong evidence of efficacy and the low risk of adverse effects, common cold patients may already be encouraged to try zinc acetate lozenges not exceeding 100 mg of elemental zinc per day for treating their colds."
Further information: Harri Hemilä, Edward J. Petrus, James T. Fitzgerald and Ananda Prasad: Zinc acetate lozenges for treating the common cold: an individual patient data meta-analysis, British Journal of Clinical Pharmacology.
Contact author: Harri Hemila, MD, PhD, Department of Public Health, University of Helsinki, harri.hemila@helsinki.fi, tel. +358-41 532 9987.