Zinc: a natural weapon against viruses?

By Ana Espino | Published on December 26, 2025 | 3 min read


Acute viral respiratory tract infections (AVRTIs), such as the common cold or influenza, impose a substantial burden at both individual and societal levels. They account for millions of medical consultations, widespread use of symptomatic treatments, productivity losses, and, in some cases, severe complications. Conventional management is largely symptomatic, with no true direct antiviral action, while antibiotic overuse remains a major concern.  

In this context, zinc—an essential trace element involved in both innate and adaptive immunity—has attracted growing interest as a natural preventive or therapeutic agent. Although some trials have reported beneficial effects, results are heterogeneous and often limited by variable methodologies. Against this backdrop, this study was conducted to evaluate the efficacy and safety of zinc in the prevention and treatment of acute viral respiratory tract infections (AVRTIs) in adults.    

Can zinc really shorten your cold?  

Twenty-eight randomized controlled trials were included. The 5,446 adults enrolled were randomly assigned to one of two groups:
  

• Prevention of AVRTIs
• Treatment of AVRTIs

 
Zinc formulations varied (gluconate, acetate, sulfate) and were administered orally, sublingually, or intranasally, at doses ranging from 15 mg to 300 mg/day, over variable durations.  

In prevention studies, zinc showed significant efficacy. Participants receiving supplementation had a 31% lower risk of developing an AVRTI. These effects were more pronounced when supplementation lasted at least 3 to 6 months, particularly during winter periods or among individuals with frequent exposure risk (healthcare workers, teachers, etc.).  

In treatment trials, results were also encouraging. Zinc reduced symptom duration by an average of 1.8 to 2.2 days and decreased symptom severity from the third day of treatment compared with placebo. The effect was stronger when supplementation began within the first 24 hours after symptom onset, highlighting the importance of early administration.

Regarding tolerability, zinc was generally well tolerated. The most common adverse effects included mild gastrointestinal disturbances (nausea, gastric discomfort), a transient metallic taste, or nasal irritation with intranasal formulations. No serious adverse events were directly attributed to zinc supplementation.    

Useful, but not a miracle  

Acute viral respiratory infections remain a major global public health issue in the absence of specific curative treatments. A key challenge lies in identifying simple, accessible, and effective interventions to prevent or mitigate these infections while reducing unnecessary antibiotic use.  

In this context, this review aimed to rigorously assess the efficacy and tolerability of zinc for both prevention and treatment of AVRTIs in adults. The findings confirm a significant beneficial effect on reducing infection risk, symptom duration, and severity—particularly when zinc is administered early. This supports the role of zinc as a complementary, natural, and well-tolerated option within a comprehensive strategy for managing viral respiratory infections.  

Nevertheless, limitations remain and justify further research. Future studies should include large-scale randomized controlled trials, standardized formulations, dosing regimens, and routes of administration. Long-term follow-up is also needed to assess safety. It will be essential to explore the impact of baseline zinc nutritional status, identify populations most likely to benefit (older adults, immunocompromised patients, zinc-deficient individuals), and evaluate how zinc supplementation could be integrated into public health policies, particularly during epidemic periods.   

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