Review of Randomized Trials Concludes Zinc Supplements Decrease Duration of Common Cold


June 16, 2020

A review of 20 randomized, controlled trials published on April 27, 2020 in the American Journal of Tropical Medicine and Hygiene concluded that supplementing with zinc is associated with a significant reduction in the length of the common cold.

“Intake of certain micronutrients enhances the immune system through strengthening epithelial barriers and cellular immunity and production of antibodies,” authors Min Xian Wang and colleagues noted. “The positive effects of micronutrient intake on the immune system suggests their potential protective role against infections.”

Recognizing the need for evaluation of nutrients other than vitamin C, whose effects in cold prevention and management have been well studied, researchers from the National University of Singapore selected 20 trials that examined the effects of supplementation with different micronutrients on the common cold among a total of 49,189 healthy adults. “There is a need to systematically assess the existing literature, specifically randomized controlled trials (RCTs), to better understand the importance and effects of all micronutrients, except vitamin C, in fending off and managing colds among healthy adults, other than in diseased and/or vulnerable populations,” the authors remarked.

Pooled results of six trials that evaluated supplementation with zinc lozenges found an average reduction in common cold duration of 2.25 days in comparison with a placebo. The trials involved zinc acetate or gluconate lozenge supplementation consumed no less frequently than every three hours while awake until the resolution of cold symptoms. “This suggests that zinc supplementation may reduce the overall burden due to common cold among healthy adults,” the authors concluded.

They noted that the limited number of trials suitable for their review highlights the need for more research focusing on micronutrients to prevent and manage colds in healthy adults, rather than in diseased, juvenile or elderly populations.


Apply What You've Learned: Zinc

  • Zinc is an essential trace mineral that is one of a number of nutrients that support immune function.1

  • Zinc lozenges, which are dissolved on the tongue several times per day, deliver zinc to the throat area and should be used at the first sign of colds or flu. Some zinc lozenges contain additional nutrients.

  • The high daily dose of zinc delivered by the recommended intake of zinc lozenges should be consumed only through the duration of a cold or flu. Consuming high daily doses of zinc for prolonged periods may create the need for a low dose copper supplement. A single daily zinc lozenge may be consumed as a preventive measure in the absence of the intake of other sources of zinc that contain high amounts of the mineral.

  • Some factors in the diet can limit zinc absorption and certain forms of zinc have greater bioavailability than other forms. Blood testing for zinc levels aids in the determination of whether zinc intake is adequately absorbed.



  1. Maares M et al. Arch Biochem Biophys. 2016 Dec 1;611:58-65.

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