Zinc: the cold remedy that partly works, and the supplement that backfires

Zinc is one of the few supplements with a real, measurable effect on the common cold. It is also one of the few where taking it every day for months causes a specific and predictable harm.

What it does in the body

• Zinc is required for the activity of hundreds of enzymes and has roles in immune function, protein and DNA synthesis, wound healing and cell division. Evidence E source

How much you need

• The RDA for zinc is 11 mg a day for adult men and 8 mg for adult women, 11 mg in pregnancy and 12 mg when breastfeeding. — adults Evidence E source
• The Tolerable Upper Intake Level for zinc is 40 mg a day for adults. — adults 19+ Evidence E source
• Doubling how much zinc a person eats moves the zinc in their blood by only about 6 per cent, which is why setting a zinc norm from blood tests is so hard. — adults; studies reporting zinc dose, study duration, dietary zinc intake and end-of-intervention plasma or serum zinc Evidence A source
• The zinc recommendation for young children is built from measured numbers: about 27 per cent of dietary zinc is absorbed, and the body loses roughly 17 micrograms per kilogram a day in urine. — healthy children aged 0 to 9 years; 94 studies covering tissue zinc content, absorption, bioavailability and endogenous losses Evidence C source
• People on habitual vegetarian diets take in about 0.88 mg less zinc a day and carry measurably less zinc in their blood. — 34 studies in the review; 26 studies reporting 48 comparisons of vegetarian and non-vegetarian groups were meta-analysed Evidence C source
• Two national food tables describe 'Oysters, raw' in exactly the same words and put their zinc 50% apart. — raw oysters Evidence E source
• Nearly seven in ten American adults fall below the zinc Daily Value, but below the actual requirement it is about four in ten, and the gap between those two numbers is the whole story. — US adults aged 19 and over, by sex and age band Evidence E source

How well your body absorbs it

• Phytates in legumes and whole grains bind zinc and inhibit its absorption, so zinc from vegetarian diets is less available. — vegetarians and vegans Evidence E source
• Measured with isotopes, a whole day's rice gave Bangladeshi preschoolers between 1.1 and 1.4 mg of absorbed zinc, less than half of the 3 mg a day a one to three year old is supposed to get. — children aged 36 to 59 months in a peri-urban community in Bangladesh, fed 150 g of conventional rice, conventional rice with added zinc, or zinc-biofortified rice as part of a mixed diet Evidence B source
• Sprouting wheat cut its phytate by a quarter and raised zinc availability in the test tube, and changed how much zinc people actually absorbed by nothing at all. — healthy adults, men and women, young adult to middle-aged Evidence B source
• The trialists drew the general lesson themselves: measuring phytate and test-tube availability does not tell you how much zinc a food will deliver. — healthy adults consuming wheat breakfast flakes Evidence B source
• Whether you eat zinc with a meal or on its own changes absorption almost fourfold, and in the direction most people would not guess. — Nigerian children aged 2-10, nineteen with nutritional rickets and fifteen age-matched controls, all given calcium 600 mg/day and ergocalciferol 1250 µg/week for six weeks first Evidence B source
• Fermenting the porridge did not lower its phytate. The enzyme did. The traditional step people are told to rely on failed the measurement. — maize porridge prepared for Nigerian children in the same study Evidence B source
• Cooking barely touches zinc: in 226 of 269 USDA methods the retention factor is 100%, and the worst figure in the entire table is 75%. — all food groups and cooking methods in the table Evidence E source

What too little does

• Zinc deficiency in older adults can delay wound healing and change cognitive and psychological function. In children it impairs growth and causes frequent infections. — older adults and children Evidence E source
• Only two measurements have been shown to track a real change in zinc intake: zinc in blood and zinc in urine. — healthy participants in studies where zinc intake was changed for at least two weeks; 32 previously reported biomarkers plus 40 further candidates assessed Evidence A source
• Taste really does blunt with low zinc: in a trial in Indian schoolgirls, ten weeks of zinc halved the amount of salt needed before they could taste it. — schoolgirls averaging 12.5 years from Pune, India, assessed at baseline and after ten weeks; taste measured as the recognition threshold across ten salt concentrations Evidence B source
• In the same trial, memory and reasoning scores rose about four times as much in the zinc groups as in the control group. — schoolgirls averaging 12.5 years from Pune, India; tests of simple and recognition reaction time, visual memory and Raven's Progressive Matrices Evidence B source
• People with patchy hair loss do have lower blood zinc than healthy controls, but that is an association measured after the fact, not proof that low zinc caused it. — patients with alopecia areata and healthy controls in 34 papers from 16 countries Evidence C source

Who is most likely to fall short

• After a gastric bypass, blood zinc falls through the first year. After a sleeve gastrectomy it largely does not. — people with obesity undergoing bariatric surgery, compared with their own pre-operative levels at 3 months, 6 months, 1 year and 2 years Evidence C source

What the evidence does and does not show

• Zinc lozenges or syrup taken soon after a cold starts appear to shorten it but not to make it milder. — adults with colds Evidence A source
• Reviewers concluded it is unclear whether zinc affects cold severity, and based all conclusions on low to very low certainty evidence. — adults with colds Evidence A source
• In the 2024 Cochrane review, zinc taken to treat a cold shortened it by about two and a third days, on low-certainty evidence. — adults and children with a cold, 8 treatment trials Evidence A source
• Taken every day to prevent colds, zinc did little or nothing: nine trials found no clear reduction in the chance of catching one. — adults and children, 9 prevention trials Evidence A source
• Zinc taken for a cold makes side effects more likely, with about a third more people reporting them. — participants of 16 treatment trials Evidence A source
• In seven studies of people with pressure sores, zinc supplements improved healing by about 44 per cent against usual nutrition care. — patients with pressure injuries, 7 studies Evidence A source
• The strongest thing zinc has ever been shown to do is keep young children alive: pooled trials show 16 per cent fewer deaths from any cause in children under five. — children under five years of age in trials of preventive or therapeutic zinc supplementation Evidence A source
• In children with acute diarrhoea zinc shortens the illness by about thirteen hours, and it makes vomiting about half again as likely. — children under ten years of age with acute or persistent watery diarrhoea Evidence A source
• Zinc given to children adds about two millimetres of height and 140 grams of weight, but it does not reduce stunting, underweight or wasting, and given in pregnancy it does nothing for birth weight. — pregnant women in 24 trials and infants and children up to five years in 54 trials Evidence A source
• In people with diabetes or prediabetes zinc lowered fasting insulin and insulin resistance, but it also nudged LDL cholesterol up, so the metabolic picture is not all in one direction. — adults with diabetes mellitus, gestational diabetes or prediabetes Evidence A source
• Added to an antidepressant, zinc moved depression scores by a moderate amount after six weeks, and the whole effect came from patients whose previous antidepressant had failed. — adults on antidepressant medication, split by whether earlier treatment in the same episode had failed to bring remission Evidence A source
• Zinc is sold hard for testosterone and male fertility. The 2026 review that traced the molecular case says the randomised evidence is still thin. — review of preclinical, observational and interventional literature on male reproductive outcomes Evidence E source

What too much does

• Doses of 50 mg zinc or more taken for weeks can interfere with copper absorption, reduce immune function and lower HDL cholesterol. — adults on long-term high-dose zinc Evidence E source
• High zinc intakes can cause nausea, dizziness, headaches, gastric distress, vomiting and loss of appetite. — adults Evidence E source
• The zinc lozenge trials used doses far above the 40 mg daily ceiling, between 45 and 276 mg a day, for up to three weeks. — participants of the lozenge trials in the review Evidence A source
• Every published case of zinc-induced blood toxicity involved doses from 50 mg a day upwards, and copper was low in every single patient. — people with anaemia, neutropenia, leukopenia, thrombocytopenia, pancytopenia or bone marrow suppression attributed to zinc exposure, from oral supplements, denture adhesive creams and coin ingestion Evidence C source
• Three oysters cover the whole daily zinc reference value, and a cup of them carries more than twice the tolerable upper limit. — oysters, raw and steamed Evidence E source

Medicines it interacts with

• Iron supplements of 25 mg or more taken at the same time as zinc can reduce zinc absorption. — people taking both supplements Evidence E source
• For zinc sprayed into the nose, the reviewers concluded that concerns about permanent loss of smell may mean the question is never settled scientifically. — adults with a common cold, 3 trials pooled Evidence A source

What to do with this

Zinc splits its readers into two groups that need opposite advice.

If you eat meat or seafood regularly, you are getting plenty and the only thing worth avoiding is the high-dose supplement habit. If you eat mostly plants, you are absorbing less than the label suggests, because phytate in legumes and grains binds zinc, and aiming somewhat higher than the headline number is the sensible response. Sesame, pumpkin seeds and cashews are good additions. Soaking, sprouting and sourdough leavening are the usual advice on top of that, and the section below explains why less of it survived testing in people than anyone expected.

Lozenges at the first sign of a cold are a short course of days. They are not a reason to take 50 mg every day through the winter, which is where zinc starts working against copper, HDL cholesterol and the immune function people are trying to protect.

One more thing if you came here because of something you read about zinc and immunity. The best evidence zinc has for doing anything at all is in children under five in countries where deficiency is common, where it cuts deaths from any cause by about 16 per cent. That is a public health result from a setting most readers of this page do not live in, and it is no argument for a well-fed adult to take a capsule every day through the winter.

Soaking and sprouting: what happened when somebody measured people

The advice to soak, sprout and ferment your grains and legumes is everywhere, this page included until today. The reasoning is sound. Phytate in grains and legumes binds zinc, those processes lower phytate, so more zinc should reach you. Somebody finally checked the last step in humans rather than in a beaker.

Myth. Sprouting your grains gets you more zinc. In healthy adults eating wheat breakfast flakes, sprouting cut the phytate by 26 per cent and raised zinc availability in the test tube 1.4-fold. How much zinc the people absorbed did not change significantly. A harsher hydrothermal treatment cut phytate by 48 per cent and raised test-tube availability almost tenfold, and still did not move absorption in people. The trialists drew the general lesson themselves: measuring phytate and test-tube availability does not tell you how much zinc a food will actually deliver.

Myth. Fermentation unlocks the zinc in porridge. In maize porridge prepared for Nigerian children, fermentation left the phytate statistically unchanged, 3.87 g/kg untreated against 3.35 after fermenting, and zinc absorption was unaffected. The traditional step people are told to rely on failed the measurement. An added phytase enzyme cut the phytate properly, to 2.83 g/kg, and doubled the zinc absorbed from the meal.

So if you eat mostly plants, the useful moves are the plain ones. Eat more zinc, from seeds, nuts, legumes and whole grains, and know that you absorb a smaller share of it than a meat eater does. Soaking and sprouting are fine for texture and for cooking time. Do not count on them for zinc.

Zinc and food work against each other, which nobody expects

Established. In the same Nigerian children, zinc absorption was 16.2 per cent when it came with a meal and 63.4 per cent when it came without one. Nearly fourfold, in the direction most people guess wrong. Calcium in the same study went the other way, 61.3 per cent with a meal against 27.8 without.

Not for everyone. That is not permission to start swallowing zinc on an empty stomach. Zinc on an empty stomach is a well-known cause of nausea, and the people in that study were children being investigated for rickets rather than adults taking a supplement by choice. The finding explains why a supplement taken with dinner does less than the label implies. What to do about it is a question for whoever suggested the supplement, and for most readers the answer is that food beats a capsule anyway.

One piece of good news that costs nothing. Cooking barely touches zinc. Across 269 cooking methods in the USDA retention table, 226 of them keep 100 per cent of it, and the worst figure anywhere in the table is 75 per cent, for pork sausage. Compare that with simmered pork keeping 40 per cent of its thiamin, and you can stop thinking about how you cook where zinc is concerned.

Oysters, and the only food on this site that can overdose you

Raw oysters run about 39.3 mg of zinc per 100 g, which makes one oyster 5.9 mg. Three of them cover the entire 11 mg Daily Value. Steamed they are denser still, 7.5 mg each.

Not for everyone. A cup of raw oysters, 225 g, carries 88.4 mg of zinc. The tolerable upper limit is 40 mg a day, so that single serving is more than twice it, and a cup of steamed oysters is 67.2 mg. Nothing else in ordinary food comes near this. One oyster dinner will not hurt you, and the upper limit is built around sustained intake rather than a single meal. Eating oysters that way weekly, on top of a zinc supplement taken for colds or immunity, is how people reach the dose that blocks copper absorption and lowers HDL cholesterol without ever swallowing a large tablet.

The oyster numbers themselves are less firm than they look. The British and American food tables both list 'Oysters, raw' and put the zinc 50 per cent apart, 59.2 mg per 100 g against 39.3. The British table also carries oysters weighed with their shells at 8.3 mg per 100 g, the same animal at a seventh of the figure, because the shell is in the denominator. Read any oyster number as an order of magnitude rather than a measurement.

How many people are actually short

Two answers circulate and they are very far apart. Against the 11 mg Daily Value on labels, 68.6 per cent of American adults fall below, and among women 79.4 per cent. Against the actual requirement the Daily Value is built from, it is 39.8 per cent of women aged 19 to 30 and 43.4 per cent of men the same age. Median intake is 8.66 mg a day, 10.05 for men and 7.65 for women.

Nearly seven in ten against about four in ten, from the same survey and the same dinners. The Daily Value is set to cover almost everybody, including the people who need the most, so being under it is an ordinary place to be. Four in ten below the requirement is still a real number, and it is the one worth carrying.

Unsettled. Zinc is sold hard for testosterone and male fertility, and the biology behind the pitch is genuine. Zinc is a cofactor in the enzymes that build testosterone, it helps hold sperm membranes together, and it affects how the tail moves. A 2026 review traced all of that and then said the quiet part: the case rests on laboratory and observational work, and the randomised evidence in men is still limited. Real mechanism, missing trials. That combination is the most common way a supplement gets sold.

Where to get it from food

The bottom line

Zinc lozenges started early can shorten a cold, though the certainty of that evidence is low and they do not make the symptoms milder. Hold that against what zinc has actually been shown to do. Pooling 28 randomised trials in 237,068 children under five, zinc cut deaths from any cause by 16 per cent, a relative risk of 0.84. That is the strongest result zinc has anywhere, and it comes from places where zinc deficiency is common, so it does not transfer to a well-fed child in a rich country. In children with acute diarrhoea zinc shortens the illness by about thirteen hours and makes vomiting about half again as likely, which is why the reviewers who ran those numbers for the World Health Organization concluded the dose should come down. On growth the picture is mostly empty. Seventy-eight trials found about two millimetres of height and 140 grams of weight, with nothing on stunting, underweight or wasting, and zinc in pregnancy did nothing for birth weight. In diabetes and prediabetes zinc lowered fasting insulin and insulin resistance while pushing LDL cholesterol up, and no trial in that set measured anything that happens to a person rather than to a blood sample. Added to an antidepressant it moved depression scores at six weeks, and the whole effect came from patients whose previous antidepressant had failed, which the authors themselves call preliminary. What you should not do is take 50 mg or more daily for weeks as a general immune measure. At that dose zinc blocks copper absorption and lowers HDL cholesterol. People on plant-based diets absorb less zinc from the same intake, and that is a better reason to pay attention to zinc than colds are. The standard advice for getting more zinc out of plant food has now been measured in people, and most of it did not survive. Sprouting wheat cut its phytate by a quarter and raised zinc availability in a test tube, and changed how much zinc people absorbed by nothing at all. Fermenting maize porridge did not even lower the phytate. What did work was an added enzyme, which doubled zinc absorption from a meal. Oysters are the other end of the scale. Three of them cover the daily reference value of 11 mg, and a cup of raw oysters carries 88 mg, more than twice the upper limit of 40 mg.

Sources

1. zn-01 · Position of an expert body · expert body statement
   Zinc is involved in many aspects of cellular metabolism. It is required for the catalytic activity of hundreds of enzymes, and it plays a role in enhancing immune function, protein and DNA synthesis, wound healing, and cell signaling and division.
   NIH Office of Dietary Supplements, Health Professional Fact Sheet: Zinc · checked 2026-09-15 · extracted
2. zn-02 · Position of an expert body · expert body recommendation
   19+ years: 11 mg [male], 8 mg [female]; Pregnancy: 11 mg; Lactation: 12 mg (value from the source's table, not a sentence)
   NIH Office of Dietary Supplements, Health Professional Fact Sheet: Zinc · checked 2026-09-15 · extracted
3. zn-03 · Position of an expert body · expert body recommendation
   19+ years: 40 mg (value from the source's table, not a sentence)
   NIH Office of Dietary Supplements, Health Professional Fact Sheet: Zinc · checked 2026-09-15 · extracted
4. zn-r3-01 · Meta-analysis or systematic review · dose-response meta-analysis of trials and observational studies
   The overall pooled β for Zn supplementation on serum/plasma Zn concentrations from randomised controlled trials and observational studies was 0·08 (95 % CI 0·05, 0·11; P < 0·0001; I² 84·5 %). An overall β of 0·08 means that for every doubling in Zn intake, the difference in Zn serum or plasma concentration is β (2(0·08) = 1·06), which is 6 %.
   British Journal of Nutrition, 2012 · checked 2026-09-17 · independently re-checked
5. zn-r3-02 · Observational data · systematic review and meta-analysis of physiological studies
   Meta-analysis revealed an overall mean (95%CI) urinary and endogenous fecal zinc excretion of 17.48 µg/kg/d (11.80-23.15; I2 = 94%) and 0.07 mg/kg/d (0.06-0.08; I2 = 82%), respectively, with a mean fractional zinc absorption of 26.75% (23.69-29.81; I2 = 99%).
   Nutrition Reviews, 2023 · checked 2026-09-17 · independently re-checked
6. zn-r3-04 · Observational data · systematic review and meta-analysis of observational studies
   Dietary zinc intakes and serum zinc concentrations were significantly lower (-0.88 ± 0.15 mg day(-1), P < 0.001 and -0.93 ± 0.27 µmol L(-1), P = 0.001 respectively; mean ± standard error) in populations that followed habitual vegetarian diets compared with non-vegetarians.
   Journal of the Science of Food and Agriculture, 2013 · checked 2026-09-17 · independently re-checked
7. zn-a-07 · Position of an expert body · reference dataset
   CoFID 16-260 Oysters, raw — Zinc (mg) 59.2 · CoFID 16-261 Oysters, raw, weighed with shells — Zinc (mg) 8.3 · FNDDS 2706351 Oysters, raw — Zinc, Zn 39.3 MG на 100 г
   CoFID 2021 (Public Health England, OGL v3.0) and USDA FNDDS 2021-2023 · checked 2026-09-21 · independently re-checked
8. zn-a-09 · Position of an expert body · national dietary survey
   zinc_mg · усі 19+ n=4886 median 8.66 mean 9.89 · Daily Value FDA (не EAR) = 11.0 floor: усі 19+ 68.6% · ж 19+ 79.4% · ч 19+ 57.1% · EAR (DRI, National Academies) floor: ж 19-30 (6.8) 39.8% проти DV 76.8% · ч 19-30 (9.4) 43.4% проти DV 56.5% · ж 71+ (6.8) 45.3% проти DV 82.5%
   NHANES 2021-2023 (DR1TOT/DEMO), weighted; EAR from DRI, National Academies · checked 2026-09-21 · independently re-checked
9. zn-04 · Position of an expert body · expert body statement
   The bioavailability of zinc from vegetarian diets is often lower than from nonvegetarian diets because people who follow vegetarian diets typically eat large amounts of legumes and whole grains, which contain phytates that bind zinc and inhibit its absorption.
   NIH Office of Dietary Supplements, Health Professional Fact Sheet: Zinc · checked 2026-09-15 · extracted
10. zn-r3-03 · Randomised controlled trial(s) · randomised crossover isotope absorption trial
    Mean FZA: 0.23 ± 0.041, 0.169 ± 0.035, and 0.212 ± 0.048 for respective diets...A single-day ration (150 g total) in 3 equally divided servings of Hi-Zn BfR could satisfy 47% of the recommended daily requirement of zinc (3 mg/d) for children 1-3-y old and 28% for children 4-8-y old (5 mg/d) compared with 37% and 23% from Lo-Zn CR for the same age groups, respectively.
    The Journal of Nutrition, 2026 · checked 2026-09-17 · independently re-checked
11. zn-a-01 · Randomised controlled trial(s) · randomised crossover isotopic absorption trial
    Sprouting of wheat did not significantly increase fractional Zn absorption, while hydrothermal processing of wheat resulted in a 1.1-fold increase in fractional Zn absorption compared to untreated wheat.
    Food & Function, 2025 · checked 2026-09-21 · independently re-checked
12. zn-a-02 · Randomised controlled trial(s) · randomised crossover isotopic absorption trial
    These findings show that assessing phytate reduction and Zn bioaccessibility values of food products alone is not sufficient to predict Zn absorption from food products.
    Food & Function, 2025 · checked 2026-09-21 · independently re-checked
13. zn-a-03 · Randomised controlled trial(s) · randomised controlled isotopic absorption trial
    Zinc absorption was lower with a meal (16.2 +/- 8.0%) than without (63.4 +/- 23.9%; P < 0.001). Enzymatic dephytinization increased relative zinc absorption from a meal by 101 +/- 81% (P < 0.001) but did not affect calcium absorption.
    Journal of Nutrition, 2009 · checked 2026-09-21 · independently re-checked
14. zn-a-04 · Randomised controlled trial(s) · randomised controlled isotopic absorption trial
    The phytate concentration of maize porridge (3.87 +/- 0.38 g/kg wet weight) was reduced by enzymatic dephytinization (2.83 +/- 0.41 g/kg; P < 0.001) but not by fermentation (3.35 +/- 0.27 g/kg; P = 0.08).
    Journal of Nutrition, 2009 · checked 2026-09-21 · independently re-checked
15. zn-a-06 · Position of an expert body · reference dataset
    zinc_mg фактори по 269 рядках: 100.0 — 226 рядків · 95.0 — 19 · 90.0 — 11 · 85.0 — 9 · 80.0 — 1 · 75.0 — 3 (SAUSAGE,RAW,PORK,OTHER,BROILED / CKD,WO/DRIP / SAUTEED) · FINFISH,<5%FAT,SIMMERED,W/DRIPPINGS — 80.0
    USDA Table of Nutrient Retention Factors, Release 6 (2007) · checked 2026-09-21 · independently re-checked
16. zn-10 · Position of an expert body · expert body statement
    Zinc deficiency in older adults can cause delays in wound healing and changes in cognitive and psychological function.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Zinc · checked 2026-09-15 · extracted
17. zn-r2-1 · Meta-analysis or systematic review · systematic review and meta-analysis
    Pooled data analysis confirmed that, in healthy participants, both plasma/serum zinc concentration and urinary zinc excretion responded to changes in zinc intake (plasma/serum: mean effect [95% CI], controlled studies: 2.17 µmol/L [1.73, 2.61]; P < .005, I2 = 97.8; before-and-after studies: 2.87 µmol/L [2.45, 3.30]; P < .005, I2 = 98.1%; urine zinc: 0.39 mmol/mol creatinine [0.17, 0.62]; P < .005, I2 = 81.2; 3.09 µmol/day [0.16, 6.02]; P = .039, I2 = 94.3).
    Ceballos-Rasgado et al., Nutrition Reviews, 2025 · checked 2026-09-17 · independently re-checked
18. zn-r2-2 · Randomised controlled trial(s) · randomised controlled trial
    A significant fall in median RTS from 5 to 2.5 mmol/L was noted after both diet and zinc supplementation (p < 0.01); however, it remained the same at 5 mmol/L in the Control group after 10 weeks.
    Tupe & Chiplonkar, Journal of the American College of Nutrition, 2009 · checked 2026-09-17 · independently re-checked
19. zn-r2-3 · Randomised controlled trial(s) · randomised controlled trial
    Percent increment in scores for memory and RPM was significantly more in the D and J groups (24.5%-29.6%) than in the C group (6.5%) (p < 0.05). Mean SRT and RRT were reduced more in the D and J groups (5%-16%) than in the C group (1.6%) (p < 0.05).
    Tupe & Chiplonkar, Journal of the American College of Nutrition, 2009 · checked 2026-09-17 · independently re-checked
20. zn-r2-4 · Observational data · meta-analysis of observational studies
    The results of meta-analysis demonstrated patients with AA had a lower serum level of vitamin D (SMD = -0.93 ng/mL, 95% CI = 0.168-0.747, p < 0.05) and serum zinc (SMD = -0.69 μg/dL, 95% CI = -0.99 to -0.39, p < 0.05) than the healthy controls.
    Wu et al., Journal of Cosmetic Dermatology, 2025 · checked 2026-09-17 · independently re-checked
21. zn-r2-5 · Observational data · systematic review and meta-analysis of observational data
    Compared with baseline, pooled standardized mean differences (SMDs) in serum zinc at 3 months, 6 months, 1 year, and 2 years postoperatively were -0.12 (95% CI: -0.27 to 0.04, I2 = 57.9%, τ2 = 0.0265, p = 0.149), -0.36 (95% CI: -0.58 to -0.14, I2 = 82.2%, τ2 = 0.1043, p = 0.001), -0.35 (95% CI: -0.53 to -0.16, I2 = 81.9%, τ2 = 0.0769, p = 0.001), and -0.36 (95% CI: -0.95 to 0.24, I2 = 97.2%, τ2 = 0.3515, p = 0.240), respectively.
    Zhu & Liu, Annals of Medicine, 2026 · checked 2026-09-17 · independently re-checked
22. zn-05 · Meta-analysis or systematic review · review of trials cited by expert body
    Supplemental zinc in lozenge or syrup form appears to reduce the duration, but not the severity, of signs and symptoms of the common cold when taken shortly after a person develops a cold.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Zinc · checked 2026-09-15 · extracted
23. zn-06 · Meta-analysis or systematic review · systematic review
    The authors also concluded that it is unclear whether zinc affects the severity of cold symptoms. They noted that all of these conclusions were based on low to very low certainty of evidence.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Zinc · checked 2026-09-15 · extracted
24. cold-z1 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis
    When zinc is used for cold treatment, there may be a reduction in the mean duration of the cold in days (MD -2.37, 95% CI -4.21 to -0.53; I² = 97%; 8 studies, 972 participants; low-certainty evidence)
    Nault et al., Cochrane Database of Systematic Reviews, 2024 · checked 2026-09-16 · independently re-checked
25. cold-z2 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis
    There may be little or no reduction in the risk of developing a cold with zinc compared to placebo (risk ratio (RR) 0.93, 95% CI 0.85 to 1.01; I2 = 20%; 9 studies, 1449 participants; low-certainty evidence)
    Nault et al., Cochrane Database of Systematic Reviews, 2024 · checked 2026-09-16 · independently re-checked
26. cold-z3 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis
    There is probably an increase in the risk of non-serious adverse events when zinc is used for cold treatment (RR 1.34, 95% CI 1.15 to 1.55; I2 = 44%; 2084 participants, 16 studies; moderate-certainty evidence)
    Nault et al., Cochrane Database of Systematic Reviews, 2024 · checked 2026-09-16 · independently re-checked
27. zn-w1 · Meta-analysis or systematic review · systematic review and meta-analysis
    The intervention group significantly had improved healing vs that of the control group (relative risk, 1.44; 95% CI, 1.01-2.06; P = 0.043, I2 = 19.3%).
    Song et al., Nutrition in Clinical Practice, 2020 · checked 2026-09-17 · independently re-checked
28. zn-r5-1 · Meta-analysis or systematic review · meta-analysis of randomised controlled trials
    Combining 30 RRs from 28 RCTs including 237,068 participants revealed that zinc supplementation has significantly reduced the risk of all-causes mortality by 16% in children (SRR: 0.84, 95% CI: 0.74, 0.96)...Zinc supplementation significantly reduced the risk of death from pneumonia (0.70: 0.64, 0.98) and infection (0.54; 0.39, 0.76), also changed the risk of mortality from diarrhea by 15% (0.85; 0.70, 1.03) and sepsis by 57% (0.43; 0.18, 1.02).
    Rouhani et al., European Journal of Nutrition, 2022 · checked 2026-09-17 · independently re-checked
29. zn-r5-2 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised controlled trials
    Our findings suggest that, in children with acute diarrhoea, zinc supplementation resulted in a greater proportion of children who recovered from diarrhoea at last follow-up (risk ratio (RR) = 1.07; 95% confidence interval (CI) = 1.03, 1.1; moderate certainty of evidence) and a reduction in the duration of diarrhoea (mean difference (MD) = -13.27 hours; 95% CI = -17.66, -8.89; moderate certainty of evidence) when compared to placebo. A significant number of children in the zinc group compared to placebo experienced vomiting (RR = 1.46; 95% CI = 1.22, 1.76; moderate certainty of evidence)
    Ali et al., Journal of Global Health, 2024 · checked 2026-09-17 · independently re-checked
30. zn-r5-3 · Meta-analysis or systematic review · meta-analysis of randomised controlled trials
    Maternal zinc supplementation did not significantly increase birth weight (weighted mean difference (WMD) = 0.08 kg, 95%CI: -0.05, 0.22) or decrease the risk of low birth weight (RR = 0.76, 95%CI: 0.52-1.11). Zinc supplementation after birth increased height (WMD = 0.23 cm, 95%CI: 0.09-0.38), weight (WMD = 0.14 kg, 95%CI: 0.07-0.21), and weight-for-age Z-score (WMD = 0.04, 95%CI: 0.001-0.087), but not height-for-age Z-score (WMD = 0.02, 95%CI: -0.01-0.06) or weight-for-height Z score (WMD = 0.02, 95%CI: -0.03-0.06).
    Liu et al., Nutrients, 2018 · checked 2026-09-17 · independently re-checked
31. zn-r5-4 · Meta-analysis or systematic review · meta-analysis of randomised controlled trials
    Zinc supplementation significantly increased plasma zinc concentrations (MD = 7.80; 95% CI 4.33 to 11.26) and improved insulin resistance, as reflected by reductions in serum insulin (MD = -2.50; 95% CI -4.69 to -0.31) and HOMA-IR (MD = -1.10; 95% CI -2.05 to -0.15). Total cholesterol decreased modestly but significantly (MD = -5.70; 95% CI -7.50 to -3.89), representing a relatively small absolute reduction, while LDL cholesterol showed a modest increase (MD = 3.46; 95% CI 1.48 to 5.43), although the clinical relevance of this finding remains uncertain.
    Loaiza-Giraldo et al., Endocrinology, Diabetes & Metabolism, 2026 · checked 2026-09-17 · independently re-checked
32. zn-r5-5 · Meta-analysis or systematic review · meta-analysis of randomised controlled trials
    After 6 weeks, we obtained the following effect sizes: Overall effect size: Hedges' g = -0.67, p = 0.03. Subgroup with documented non-remission: Hedges' g = - 0.97, p = 0.001. Group without documented non-remission -0.35, p = 0.24. After 12 weeks: Overall effect size: Hedges' g = -1.0, p = 0.03.
    Donig and Hautzinger, Nutritional Neuroscience, 2022 · checked 2026-09-17 · independently re-checked
33. zn-a-05 · Position of an expert body · scoping review
    Zinc has been primarily shown in experimental and observational studies to act as a cofactor in enzymes of testosterone biosynthesis, preserve sperm membrane phospholipid integrity through metallothionein binding, and modulate flagellar dynein ATPase activity; however, randomized controlled evidence remains limited.
    Journal of Health, Population and Nutrition, 2026 · checked 2026-09-21 · independently re-checked
34. zn-07 · Position of an expert body · expert body statement
    If used for weeks, doses of 50 mg zinc or more...can interfere with copper absorption (which can cause low copper status), reduce immune function, and lower HDL cholesterol levels.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Zinc · checked 2026-09-15 · extracted
35. zn-08 · Position of an expert body · expert body statement
    High zinc intakes can cause nausea, dizziness, headaches, gastric distress, vomiting, and loss of appetite.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Zinc · checked 2026-09-15 · extracted
36. cold-z5 · Meta-analysis or systematic review · Cochrane systematic review
    Zinc gluconate was given at doses between 45 and 276 mg/day for between 4.5 and 21 days.
    Nault et al., Cochrane Database of Systematic Reviews, 2024 · checked 2026-09-16 · independently re-checked
37. zn-r3-05 · Observational data · systematic review of case reports and case series
    Thirty-four publications describing 37 individual cases were included, spanning from 1972 to 2025. Zinc exposure most commonly resulted from oral supplements, denture adhesive creams, and coin ingestion, with reported daily elemental zinc doses ranging from approximately 50 mg to more than 1500 mg and exposure durations ranging from weeks to years...Serum copper levels were reduced in all patients.
    Biological Trace Element Research, 2026 · checked 2026-09-17 · independently re-checked
38. zn-a-08 · Position of an expert body · reference dataset
    Oysters, raw · Zinc, Zn 39.3 MG на 100 г [fdc_id 2706351] · 1 oyster 15 г 5.9 MG · 1 cup 225 г 88.4 MG || Oysters, steamed · Zinc, Zn 49.75 MG на 100 г [fdc_id 2706353] · 1 oyster 15 г 7.5 MG · 1 cup 135 г 67.2 MG
    USDA FNDDS 2021-2023 and 21 CFR 101.9(c)(8)(iv) · checked 2026-09-21 · independently re-checked
39. zn-09 · Position of an expert body · expert body statement
    Taking supplements that contain 25 mg elemental iron or more at the same time as zinc supplements can reduce zinc absorption and plasma zinc concentrations.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Zinc · checked 2026-09-15 · extracted
40. cold-z6 · Meta-analysis or systematic review · systematic review and meta-analysis
    Unquantified concerns about permanent anosmia followingthe use of intranasal zinc may mean that the issues raised will never be scientifically resolved.
    Hulisz et al., Journal of Primary Health Care, 2009 · checked 2026-09-16 · independently re-checked