A claim you hear on longevity podcasts

Does zinc help with colds?

The claim checked: Zinc helps fight viral infections and may make cold symptoms shorter and milder Hear it at 21:41

What do the studies say?

Leaning for

Pooled trials found zinc lozenges shortened colds, by 2.73 days in one analysis; prevention results were mixed, and COVID-19 trials found no benefit.

Computed from 10 studies that test this point, each judged by two readers, in full. 10 more studies are waiting for a full read and do not count yet.

What was said on the podcast?

“it's essential mineral that supports immune system and it fights off viral infection it helps stop viral replication or you know viruses uh you know just kind of breeding I guess you call it uh some studies suggest it actually even helps reduce the duration and the severity of cold symptoms”
Mark Hyman, The Dr. Hyman Show · 5 Foods I Eat Every Day to Avoid Getting Sick · 21:41 on YouTube
Comes up in 19 episodes of the show.
The point checked Leaning for

Zinc supports immune function and fights off viral infection (helps stop viral replication)

Agree 3

pooled analysis · 2021

“In adult populations in which zinc deficiency is unlikely, our review found when zinc was used for prophylaxis, there was a lower risk of contracting a clinical illness consistent with a community-acquired viral RTI, but not following direct HRV inoculation.”

Zinc for the prevention or treatment of acute viral respiratory tract infections in adults: a rapid systematic review and meta-analysis of randomised controlled trials. BMJ Open
Who: Generally healthy adults (mean age around 37 years) at risk of or with mild to moderate viral respiratory tract infections, community-acquired or from human rhinovirus inoculation; none with SARS-CoV-2
PMID 34728441

pooled analysis · 2016

“The one stage meta‐analysis gave an overall estimate of 2.73 days (95% CI 1.8, 3.3 days) shorter colds by zinc acetate lozenge usage.”

Zinc acetate lozenges for treating the common cold: an individual patient data meta-analysis. Br J Clin Pharmacol
Who: Adults (age 17-61) with naturally acquired common colds in three randomized placebo-controlled trials
PMID 27378206

pooled analysis · 2015

“There was no substantial heterogeneity between the three trials in the effect of zinc acetate lozenges on total common cold duration (P = 0.2; I 2 = 41%), and a pooled estimate of a 42% reduction in the total duration of the colds was obtained (Figure 1 ).”

The effectiveness of high dose zinc acetate lozenges on various common cold symptoms: a meta-analysis. BMC Fam Pract
Who: Adults with natural common cold infections in randomized, double-blind, placebo-controlled trials
PMID 25888289

Partly agree 5

systematic review · 2022

“No trials investigated the effect of selenium supplementation on COVID-19, while the very few studies on the effects of zinc supplementation did not confirm efficacy.”

Zinc and selenium supplementation in COVID-19 prevention and treatment: a systematic review of the experimental studies. J Trace Elem Med Biol
Who: systematic review of clinical trials of zinc or selenium for COVID-19 prevention/treatment (uninfected exposed adults to hospitalised patients)
PMID 35217499

pooled analysis · 2021

“Vitamin D, vitamin C and zinc shortened the duration of ARI symptoms by 6%–59%.”

Effect of micronutrient supplements on influenza and other respiratory tract infections among adults: a systematic review and meta-analysis. BMJ Glob Health
Who: Adults (mean age >=18) in RCTs of micronutrient supplementation for acute respiratory infections, mostly in high-income countries; zinc trials in the USA, UK, Denmark and Australia
PMID 33472840

systematic review · 2024

“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.”

Zinc for prevention and treatment of the common cold. Cochrane Database Syst Rev
Who: RCTs of children and adults testing zinc vs placebo for common cold/URTI
PMID 38719213

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systematic review · 2020

“Overall, the results suggest that micronutrients other than vitamin C may have limited effects on cold prevention among healthy adults, but zinc shows potential reduction of cold duration.”

Zinc Supplementation Reduces Common Cold Duration among Healthy Adults: A Systematic Review of Randomized Controlled Trials with Micronutrients Supplementation. Am J Trop Med Hyg
Who: Healthy adults aged 18-65 years in RCTs of single oral micronutrients (zinc, vitamin D, vitamins A and E); zinc trials mostly in the United States with naturally acquired or experimental colds
PMID 32342851

pooled analysis · 2022

“Zinc supplementation was not associated with a significant reduction in mortality among COVID-19 patients (RR 0.79, 95% CI 0.60–1.03, P = 0.08, I 2 = 0%, Fig. 4 A).”

Clinical significance of micronutrient supplements in patients with coronavirus disease 2019: A comprehensive systematic review and meta-analysis. Clin Nutr ESPEN
Who: Adult patients with COVID-19, mostly hospitalized (mean age 55, 58.8% male), zinc subset of a 26-study micronutrient meta-analysis
PMID 35331487

Disagree 2

controlled trial · 2021 · landmark

“These interventions did not significantly shorten the duration of symptoms associated with the virus compared with usual care.”

Effect of High-Dose Zinc and Ascorbic Acid Supplementation vs Usual Care on Symptom Length and Reduction Among Ambulatory Patients With SARS-CoV-2 Infection: The COVID A to Z Randomized Clinical Trial. JAMA Netw Open
Who: adult outpatients newly diagnosed with SARS-CoV-2 by PCR in Ohio and Florida (mean age 45.2, 61.7% women), open-label
PMID 33576820

pooled analysis · 2021

“Zinc supplementation did not have any beneficial impact on the course of COVID-19 evaluated as survival to hospital discharge and in-hospital mortality.”

Should we supplement zinc in COVID-19 patients? Evidence from a meta-analysis. Pol Arch Intern Med
Who: Patients with confirmed COVID-19 (mostly hospitalized) in Egypt and the United States; one trial of ambulatory patients
PMID 34180610

What else was said but not tested?

  • Some studies suggest zinc reduces the duration and severity of cold symptoms
  • Food sources: grass-fed meat, pumpkin seeds, oysters, cashews, salmon, sardines

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