Zinc for prevention and treatment of the common cold
Nault D, et al
Published in Cochrane Database of Systematic Reviews
Methodology
Cochrane systematic review searching CENTRAL, MEDLINE, Embase, CINAHL and LILACS to 22 May 2023 and Web of Science plus two trial registries to 14 June 2023, including randomised placebo-controlled trials of zinc alone (not combined with other vitamins or minerals) in children or adults; Cochrane risk of bias tool and GRADE certainty assessment.
Key Findings
This Cochrane review included 34 randomised trials (15 prevention, 19 treatment) with 8,526 participants. For prevention, zinc showed little or no reduction in the risk of developing a cold (RR 0.93, 95% CI 0.85 to 1.01; 9 studies, 1,449 people; low certainty) and no clear difference in cold duration (MD -0.63 days, 95% CI -1.29 to 0.04; moderate certainty). Used as treatment, zinc may shorten a cold by about 2.4 days (MD -2.37, 95% CI -4.21 to -0.53; 8 studies, 972 people), but heterogeneity was extreme (I-squared 97%) and certainty low, with no clear effect on symptom severity. Zinc treatment probably increases non-serious side effects such as bad taste and nausea (RR 1.34, 95% CI 1.15 to 1.55; 16 studies, 2,084 people; moderate certainty).
Conclusions
The findings suggest that zinc supplementation may have little or no effect on the prevention of colds but may reduce the duration of ongoing colds, with an increase in non-serious adverse events.
Limitations
Most trials were at unclear or high risk of bias in at least one domain, doses and forms varied enormously (zinc gluconate 45-276 mg/day for 4.5-21 days), and the duration result carries I-squared of 97% with only low-certainty evidence.
Supplements Studied
The findings suggest that zinc supplementation may have little or no effect on the prevention of colds but may reduce the duration of ongoing colds, with an increase in non-serious adverse events.
Outcomes Measured
Zinc had little or no effect on preventing colds, with uncertain evidence for reducing duration.
Related Health Concerns
Study Details
Access Study
Disclosures
Funding
Cochrane Complementary Medicine funded by the US National Institutes of Health, National Center for Complementary and Alternative Medicine (R24 AT001293); no author conflicts of interest declared.
This information is for educational purposes only. Always consult a healthcare professional before starting any supplement regimen.