The average cold lasts approximately one week. Evidence suggests that zinc lozenges reduce the duration and severity of a cold, but controversy exists regarding the optimal form of zinc delivery. Findings from a 2017 meta-analysis suggest that the form of zinc lozenges is not important.
Zinc lozenges commonly provide zinc as either zinc gluconate or zinc acetate. The lozenges often contain sweeteners (natural or artificial), vitamins (typically vitamin C), bioactive compounds such as citric acid, and/or other ingredients. Evidence suggests that citric acid binds zinc ions, thereby reducing zinc’s effectiveness.
The authors of the meta-analysis drew on data from seven placebo-controlled zinc lozenge trials involving 575 children and adults. The doses used in the studies ranged from 80 to 207 milligrams per day, using zinc gluconate (four trials) and zinc acetate (three trials).
Their analysis revealed that zinc acetate lozenges shortened the duration of colds by 40 percent, and zinc gluconate lozenges shortened colds by 28 percent. The analysis also demonstrated that dose had very little influence on the effectiveness of zinc lozenges in reducing the duration of a cold, with both high and low doses reducing duration by about one-third. The authors of the analysis concluded that zinc lozenges delivering doses greater than 80 milligrams per day reduce the duration of a cold, regardless of the form of zinc provided, as long as the lozenge does not contain ingredients that bind zinc.