Supplement · graded by use, three uses
Zinc
Common-cold duration in adults.
Zinc is a mineral the body needs in small amounts. In adults, zinc lozenges shortened colds by about two and a half days. The effect came from lozenges giving about 80 to 90 milligrams a day, and a low-dose lozenge did not help. In children, zinc did not shorten colds. Taking high doses for a long time can drain the body's copper and cause anemia or nerve damage that does not always reverse.
The B belongs to one of the three uses graded on this record. The other two carry their own letters.
As studied, and the trials
Science et al. (CMAJ, 2012; PMID 22566526) found colds 2.63 days shorter in adults; Hemilä et al. (Br J Clin Pharmacol, 2016; PMID 27378206) found 2.73 days in individual patient data from 3 lozenge trials; Hemilä and Chalker (BMC Fam Pract, 2015; PMID 25888289) tie the effect to 80 to 92 mg a day; the 13 mg lozenge trial was null (Hemilä et al., BMJ Open, 2020; PMID 31980506). Replicated The same finding reproduced by a separate research group. A result seen once can be chance or bias; a replicated one is harder to explain away., on a self-reported endpoint The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score., which caps the letter at B. The Cochrane review this record used to cite was withdrawn in 2015 and no longer supports anything here.
As studied, and the trials
Science et al. (CMAJ, 2012; PMID 22566526): in children the pooled effect on cold duration was not significant (0.26 days shorter, 95% CI -0.25 to 0.78). Randomized evidence exists and it is not positive in this group, so the adult result does not transfer: C.
As studied, and the trials
AREDS (Age-Related Eye Disease Study Research Group, Arch Ophthalmol, 2001; PMID 11594942): 3,640 adults aged 55 to 80 with signs of macular degeneration, followed an average 6.3 years. Against placebo An inactive substitute made to look like the real treatment, so participants cannot tell which one they received., antioxidants plus zinc lowered the odds of advanced disease (odds ratio 0.72, 99% CI 0.52 to 0.98); zinc alone did not reach the trial's significance level overall (0.75, 0.55 to 1.03) and did once the 1,063 lowest-risk participants were set aside (0.71, 0.52 to 0.99). One trial, positive mainly for the combination and for zinc alone only in the higher-risk subgroup, and not repeated against placebo by an independent group: C. The photographs were graded by masked readers. This does not grade zinc for preventing macular degeneration in people without signs of it.
Read the grade that matches your goal. How EBL grades by use →
- Dose studied
- 75 mg/day (lozenge)
- Form graded
- Zinc picolinate or gluconate (forms used in trials)
- Evidence behind the B
- PMID 22566526 →PMID 27378206 →PMID 25888289 →PMID 31980506 →
A letter describes the human evidence, not the product, the manufacturer, or the ingredient's worth.
See the full evidence record →Zinc lozenges for common-cold duration in adults, graded on published human trial evidence.
As studied: dose, form, population and duration for every use
A grade describes the intervention that was tested. Where the product on the shelf differs from it, this says so.
How this letter has changed · latest: October 2026 · Added
AREDS (Age-Related Eye Disease Study Research Group, Arch Ophthalmol, 2001; PMID 11594942) found zinc 80 mg with copper, combined with antioxidants, slowed progression to advanced macular degeneration in 3,640 adults with signs of the disease; zinc alone reached significance only in the higher-risk group. One trial, not independently repeated against placebo, is C. The record's top letter does not change.PMID 11594942
The zinc record rested on one citation, Singh and Das (Cochrane Database of Systematic Reviews A review that searches for every study on a question using a method set in advance, then assesses them together., 2013; PMID 23775705), which Cochrane withdrew in 2015. It is replaced by Science et al. (CMAJ, 2012; PMID 22566526), Hemilä et al. (Br J Clin Pharmacol, 2016; PMID 27378206), Hemilä and Chalker (BMC Fam Pract, 2015; PMID 25888289) and Hemilä et al. (BMJ Open, 2020; PMID 31980506). They agree that lozenges supplying about 75 to 92 mg of zinc a day, started early, shorten colds in adults by roughly two and a half days, that a 13 mg lozenge did not, and that children showed no significant effect. The B now names that use, form and dose; children are graded C; deficiency correction is no longer part of the graded use.PMID 23775705 PMID 22566526 PMID 27378206 PMID 25888289 PMID 31980506
Every change to a letter on this site is dated and published. The full evidence log →
Commercial disclosure
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No dose is published here. This record carries no authored dose, because the cited trials do not converge on a single figure. Each trial cited on this page states the dose it used, and EBL has not turned those into a recommendation.
Standardized forms were used in the cited trials; product quality varies.
The trial of the 13 mg lozenge had it taken six times a day (PMID 31980506). The pooled analyses give daily amounts from lozenges taken through the day and do not state clock times (PMID 22566526, PMID 27378206).
Checked against the published summaries; the full papers could not be read. What the cited trials did, not a schedule. Every supplement, by trial timing →
Long-term use above the upper intake level without copper. Sustained high-dose zinc induces intestinal metallothionein, which traps copper and can produce a copper-deficiency anemia or a myelopathy that does not always reverse.
Quinolone and tetracycline antibiotics: zinc chelates them in the gut and reduces absorption of both, which is a separation-in-time problem. Penicillamine and bisphosphonates, the same way. Thiazide diuretics increase urinary zinc loss. Copper: the interaction that matters most here is with a nutrient rather than a drug.
Sustained high-dose zinc causes copper deficiency. Prolonged high-dose zinc induces intestinal metallothionein and traps copper, producing copper-deficiency anemia and a myelopathy that does not reliably reverse on stopping. Kumar (Mayo Clinic Proceedings, 2006; PMID 17036563): copper deficiency myelopathy, case series and review. Jaiser and Winston (Journal of Neurology, 2010; PMID 20232210): review of copper deficiency myelopathy including the zinc-induced cases.
Serum zinc at baseline and 8 weeks: deficiency is common in older adults and the supplementation benefit is most pronounced when correcting a deficit. Also monitor copper levels at 12 weeks if supplementing above 15 mg/day, as zinc and copper compete for absorption. For immune applications, track frequency of upper respiratory infections over a 6-month period.
Primary evidenceFour papers, each linked to its PubMed record.
Science et al. (CMAJ, 2012; PMID 22566526): meta-analysis A study that pools the numbers from several trials into one combined estimate. of 17 randomized trials, 2,121 participants; zinc shortened colds by 2.63 days in adults (95% CI 1.58 to 3.69 days) and had no significant effect in children (0.26 days, 95% CI -0.25 to 0.78), with very high heterogeneity How much the results of the pooled trials differ from each other. High heterogeneity makes a combined estimate less reliable.. Hemilä et al. (British Journal of Clinical Pharmacology, 2016; PMID 27378206): individual patient data from 3 randomized trials of zinc acetate lozenges, 199 patients; colds 2.73 days shorter. Hemilä and Chalker (BMC Family Practice, 2015; PMID 25888289): the effect comes from lozenges supplying 80 to 92 mg of zinc a day. Hemilä et al. (BMJ Open, 2020; PMID 31980506): a randomized trial of a 13 mg lozenge taken six times a day found no difference in recovery (rate ratio 0.68, 95% CI 0.42 to 1.08), so the dose matters. Grade B on self-reported cold duration in adults, which caps at B. Correcting zinc deficiency is not graded: no cited trial measured a clinical outcome in deficient people, and a rise in blood zinc is a level of the supplement itself.
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These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. The grade on this page describes the strength of published human trial evidence in the populations studied. It is not a recommendation for any individual and is not medical advice. Starting, stopping or changing any supplement or medication is a decision for your physician.
Trials report an average. This box says whether any trial on this record looked at who the result applies to, and what it found.
For Slowing progression to advanced age-related macular degeneration in people at high risk (zinc 80 mg with copper), Grade C · Subgroup tested, effect differedAREDS (Age-Related Eye Disease Study Research Group, Arch Ophthalmol, 2001; PMID 11594942) found zinc alone short of significance across all 3,640 participants, and significant once the 1,063 at lowest risk of progression were set aside. The effect was seen in people already at higher risk of advanced disease. A subgroup result shows who the effect appeared in within these trials. It does not change the letter.
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How EBL searched for the trials (1 search)
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zinc[tiab] AND "common cold"[tiab] AND (meta-analysis[pt] OR randomized controlled trial[pt])Grades move when new trials publish. A free monthly email lists every grade EBL moved, with the reason and the trial behind it: the sign-up is on the Evidence Log →