Key takeaways
- Zinc is needed for thymulin, a thymus hormone that young T cells rely on, and men fed a low-zinc diet for 28 weeks showed weaker natural killer cells and a drop in a key T-cell signal12.
- In six trials of 5,193 young children, daily zinc cut pneumonia from about 343 to 299 cases per 1,000, though Cochrane rated the evidence low certainty8.
- In late 2024, WHO kept zinc as a standard treatment for diarrhea in children up to age 10 but suggested a lower dose, 5 milligrams a day for up to 14 days, because higher doses cause more vomiting567.
- In a Boston-area study of 617 nursing home residents, those with normal blood zinc had about half the pneumonia risk of those with low zinc, a link that still awaits proof from a trial9.
- In a Cleveland Clinic trial of 214 outpatients with COVID-19, 50 milligrams of zinc a day didn’t speed recovery10.
In 1958, a physician named Ananda Prasad arrived in Shiraz, Iran, to help build a medical school’s teaching program. Within two weeks, the chief resident brought him a case he would spend his career explaining1.
The patient was 21 but looked about 10. He had never gone through puberty, his liver and spleen were swollen, and he had severe anemia without any blood loss1. He lived mostly on bread and a few vegetables, ate no animal protein, and swallowed about a pound of clay a day1.
Prasad suspected that compounds in the bread and clay were blocking his body from absorbing iron and zinc1. Ten more patients like him soon came under his care, and Prasad’s later summaries of such cases listed repeated infections among their problems2. In Egypt, where Prasad later studied young men with the same stunted growth, zinc brought the first signs of puberty within 7 to 12 weeks2.
Scientists formally recognized zinc deficiency in people in 196313. Prasad went on to show that zinc matters for the immune system, too1.
Our zinc lozenge article covers colds, nasal zinc and copper. This one covers what zinc does in immune cells, who runs low, where it saves children’s lives, and how it fared against COVID-19.
Zinc keeps immune cells growing and talking
Zinc is a working part of more than 300 enzymes and nearly 2,000 proteins that switch genes on and off, Prasad wrote in 201213. Immune cells multiply fast when germs arrive, and that work leans on zinc4.
A 2016 review in the journal Archives of Biochemistry and Biophysics found that both branches of the immune system need zinc to develop and stay in shape4. The innate branch acts fast. The adaptive branch learns and remembers.
When zinc runs short, the review found, lymphocytes (the white blood cells behind immune memory) form, switch on and mature poorly4. Cells that swallow germs work less well. In deficiency, the thymus, the gland where T cells train, can shrink, and lymphocyte counts can fall4.
Prasad’s team traced part of the reason. Zinc is needed for thymulin, a thymus hormone that helps young T cells grow and specialize1. It’s also needed to make interleukin-2 and interferon-gamma, two chemical messengers that help coordinate an immune attack1.
A test in people. At the University of Michigan, Prasad’s group moved adult male volunteers from a normal hospital diet with about 12 milligrams of zinc a day to a soy-based diet with only 3 to 5 milligrams2. They stayed on it for 28 weeks.
Their natural killer cells, which destroy infected cells, became less active. Their T cells made less interleukin-2, and thymulin activity fell2. Taste dulled, night vision weakened and lean muscle shrank. Then the men ate zinc-fortified cookies with 27 milligrams a day for 12 weeks2.
That experiment was small, and the account we read doesn’t say how many men took part. Much of the cell-by-cell detail comes from lab research4. What people show clearly is the big picture: a real shortage weakens defenses.
Who runs low today, and why a blood test can mislead
Prasad estimated that nearly 2 billion people in poorer countries may get too little zinc, often because their diets lean on cereal grains rich in phytates, plant compounds that block absorption13. That’s an estimate, not a count.
In the U.S., most people get enough. Still, about 11% of pregnant women take in less than the average requirement, according to the NIH Office of Dietary Supplements (ODS), citing national survey data3. Pregnancy raises daily needs by 3 milligrams and breastfeeding by 43.
ODS names children with sickle cell disease, people with Crohn’s disease or ulcerative colitis, people who’ve had weight-loss surgery, vegetarians and vegans, people with alcohol use disorder, and breastfed babies over 6 months as groups that may have trouble getting enough12.
Checking is harder than it sounds. ODS lists a healthy blood level as 80 to 120 micrograms per deciliter, and levels below about 70 in women or 74 in men as a sign of low status3.
But blood zinc can shift during an infection, and it doesn’t always track what a person eats3. ODS says clinicians weigh a person’s risk factors and signs, not a single number3. Our lozenge article explains other reasons the test wobbles.
For children in poorer countries, zinc saves lives, at a new dose
Preventing pneumonia. In 2016, Cochrane reviewers at the Aga Khan University pooled six trials with 5,193 children ages 2 months to 5 years8. Most trials gave 10 milligrams of zinc gluconate or zinc sulfate a day for four to six months8.
Pneumonia fell from about 343 to 299 cases per 1,000 children8. By our math, that’s 44 fewer cases per 1,000, or about 13% fewer. The benefit was clearer when a chest exam or X-ray confirmed pneumonia, and unclear when fast breathing alone was the test8.
The reviewers rated the evidence low certainty because of gaps in how trials were reported8. They reported no outside funding and no conflicts8.
Treating pneumonia is another matter. ODS describes a 2020 review of 11 trials in which children got 10 to 20 milligrams a day for one to two weeks alongside standard care3. Zinc didn’t speed recovery or lower deaths. A smaller 2018 analysis of six trials did find fewer deaths from severe pneumonia3. A summary of WHO’s 2024 guideline lists no zinc recommendation for treating pneumonia6.
Treating diarrhea. WHO and UNICEF endorsed zinc for children’s diarrhea in 2004, and the usual dose for children under 5 has been 10 to 20 milligrams a day14. Our lozenge article covers the older evidence. What’s new is the dose.
WHO commissioned a review from Aga Khan University researchers, published in 20247. It pooled 38 trials and found zinc shortened acute diarrhea by about 13 hours7. But children on zinc were 46% more likely to vomit, and lower doses caused less vomiting than higher ones7.
WHO’s guideline on pneumonia and diarrhea in children up to age 10, published at the end of 2024, kept its strong recommendation to give zinc for both acute watery diarrhea and persistent diarrhea, based on moderate-certainty evidence56. It now suggests a 5-milligram daily dose of oral zinc for up to 14 days, a conditional recommendation based on low-certainty evidence56. It also notes that zinc gluconate causes less vomiting than other forms5.
For American parents, the lesson is narrow. These are treatment doses given to sick children, mostly where deficiency is common. Children’s upper limits are far below adults’ (12 milligrams a day at ages 4 to 8), so ask your pediatrician before giving zinc312.
In nursing homes, low zinc tracked with more pneumonia
ODS says marginal zinc intakes are possible in older adults3.
In 2007, a Tufts University team led by Simin Nikbin Meydani reported on 617 residents of 33 Boston-area nursing homes9. All had been in a year-long vitamin E trial, and everyone took a daily pill with half the recommended amounts of several vitamins and minerals, zinc included9.
Residents whose blood zinc was normal had about half the risk of pneumonia of those whose zinc stayed low9. When low-zinc residents did get pneumonia, they recovered more slowly and needed antibiotics longer9. Their death rate from any cause was 39% lower, too9.
That’s a striking link, but it isn’t proof. Low zinc may simply mark frailer, sicker people. The release didn’t give the underlying rates, so we can’t turn those percentages into cases per 1,000. The researchers said a clinical trial was the next step9.
Their funding came from the U.S. Department of Agriculture and NIH. A vitamin maker, then Hoffmann-La Roche and now DSM Nutritional Products, prepared the study capsules9.
What this means at home: if an older relative is eating less, ask whether zinc should be part of a nutrition check. ODS lists slow wound healing and trouble with thinking and memory among signs of low zinc in older adults, and notes these can have other causes12. Our companion article on nutrition and immunity explains why older adults’ diets so often fall short.
COVID-19 gave zinc a fast, public test
Early in the pandemic, some sellers claimed zinc could prevent or treat COVID-19, and regulators went after them, as our immune-boosting article explains. Researchers ran trials.
The Cleveland Clinic trial. From April to October 2020, in a trial called COVID A to Z, Cleveland Clinic researchers randomly assigned adult outpatients with COVID-19 to 10 days of zinc gluconate (50 milligrams a day), vitamin C (8,000 milligrams a day), both, or usual care10. They planned to enroll 520 people.
They stopped at 214 because the supplements weren’t helping10. Symptoms took a mean of 5.9 days to drop by half on zinc, compared with 6.7 days on usual care, a gap that could easily be chance10. Hospital stays and deaths didn’t differ10. Patients knew what they were taking, and there was no placebo.
The Tunisian trial. In 2022, doctors at hospitals in Tunisia gave 470 adults with COVID-19 either 25 milligrams of zinc twice a day for 15 days or a matching placebo11. Neither patients nor doctors knew who got what.
Death or ICU admission within 30 days occurred in 10.4% of the zinc group and 16.7% of the placebo group11. By our math, that’s about 63 fewer per 1,000. Most of the gap came from ICU stays, 5.2% compared with 11.3%11. Deaths, 6.5% compared with 9.2%, weren’t clearly different11.
Three cautions. The funding came from the Tunisian company Opalia Recordati, which makes the zinc product used11. The paper has small internal slips, such as the same confidence interval printed for two different results11. And emergency physician Justin Morgenstern, who reviews studies on his First10EM site, noted that the trial’s registry listed death alone as the main outcome, which didn’t reach significance15.
One small trial found nothing for outpatients. One company-funded trial, mostly in hospitalized patients, found fewer ICU stays but no clear drop in deaths. That isn’t enough to treat COVID-19 with zinc.
What the evidence shows
| Claim | Evidence level | What it rests on |
|---|---|---|
| Real zinc deficiency weakens immune defenses | Human deficiency cases, a controlled diet study and lab work agree124 | |
| Zinc helps treat diarrhea in children | WHO 2024 strong recommendation, moderate certainty57 | |
| 5 mg works as well as higher doses for children’s diarrhea | WHO conditional suggestion, low certainty; less vomiting57 | |
| Daily zinc prevents pneumonia in young children | 44 fewer cases per 1,000; low certainty8 | |
| Zinc speeds recovery from pneumonia in children | 11 trials: no faster recovery or fewer deaths3 | |
| Normal zinc protects older adults from pneumonia | One observational nursing home study9 | |
| Zinc shortens COVID-19 in outpatients | Trial stopped for futility10 | |
| Zinc keeps hospitalized COVID-19 patients out of the ICU | One company-funded trial; deaths not clearly lower1115 | |
| More zinc means stronger immunity | 50 mg or more a day for weeks can weaken immune function3 |
The zinc status check
Find the row that fits you. Food sources come from ODS12; the lozenge article lists amounts.
| If you are… | Why zinc may run low | Food first | Ask a clinician when… |
|---|---|---|---|
| 65 or older and eating less | Marginal intakes; low zinc tracked with pneumonia in nursing homes39 | Meat, fish, poultry, eggs, dairy at meals12 | Wounds heal slowly or memory slips12 |
| Vegetarian or vegan | Phytates in beans and grains block absorption12 | Beans, nuts, whole grains, fortified cereal12 | Taste or smell fades12 |
| Living with Crohn’s, ulcerative colitis or after weight-loss surgery | The gut absorbs less12 | Zinc-rich foods12 | At routine visits, ask whether zinc belongs in your lab checks3 |
| Drinking heavily | Alcohol use disorder goes with low zinc12 | Regular meals with protein foods12 | Taste or smell fades12 |
| Pregnant or breastfeeding | Needs rise by 3 to 4 mg a day3 | Meat, poultry, beans, fortified cereal12 | Before adding zinc beyond your prenatal vitamin12 |
| Raising a breastfed baby over 6 months | Breast milk’s zinc falls over the months3 | Zinc-rich foods from the list below, as solids begin12 | Growth slows or diarrhea lingers12 |
| Caring for a child with sickle cell disease | High risk of low zinc312 | Zinc-rich family meals12 | Ask the care team whether zinc could help growth and infections3 |
| Taking a thiazide water pill long term | More zinc leaves in urine3 | Zinc-rich foods12 | Ask your pharmacist about zinc; don’t change the medicine on your own312 |
Food first, and what Prasad’s patients teach
Prasad’s first patient lived on bread and clay1. For most people, the fix is a varied plate, not a pill.
Oysters have very high amounts. Meat, fish, poultry, crab, lobster and fortified breakfast cereals add plenty, and beans, nuts, whole grains, eggs and dairy add some12. Old kitchen habits such as soaking and fermenting beans and grains help with phytates, as our lozenge and vegan articles explain.
If you do take a supplement, ODS says it isn’t clear that zinc sulfate, acetate or gluconate is better than the others12. Count every source. The adult upper limit is 40 milligrams a day from food and supplements together, and it’s lower for children3. Zinc can also block some antibiotics and penicillamine, so space them as your label or pharmacist directs; our interaction-chart article has the details312.
Natural-health traditions will recognize this story. Human zinc deficiency was first found in people eating a very narrow diet1. But for a sick child where deficiency is common, a small zinc tablet is medicine, and WHO treats it that way5.
Questions readers ask
Should I take zinc to protect myself from COVID-19?
The trials we found tested zinc as a treatment, not as prevention. A Cleveland Clinic trial found no faster recovery in outpatients, and a company-funded Tunisian trial found fewer ICU stays but no clear drop in deaths1011. Neither supports relying on zinc.
Can a blood test tell me if I’m low?
It helps, but it isn’t decisive. Blood zinc can shift during an infection and doesn’t always reflect what you eat, so clinicians weigh your diet, health conditions and symptoms too3.
Why does WHO give zinc to children but not to me for a cold?
The situations differ. In children with diarrhea, mostly where deficiency is common, many trials show a benefit7. In adults, a 2024 Cochrane review found zinc did little or nothing to prevent colds, and 50 milligrams or more a day for weeks can weaken immune function3.
Is a multivitamin’s zinc enough for an older parent who eats poorly?
It may help fill a gap, but food comes first, and a clinician can check for deficiency312. Count the multivitamin’s zinc toward the 40-milligram daily limit3.
The bottom line
Zinc is a small mineral with a big job in the immune system. A real shortage weakens defenses, and correcting one helps, most clearly for young children in poorer countries, where WHO now suggests a gentler dose for diarrhea.
For most well-fed Americans, extra zinc adds little, and the COVID-19 trials didn’t change that. The people worth a closer look are older adults who eat less, plant-based eaters, people with gut disease or heavy drinking, and children with sickle cell disease. For them, a varied plate and a clinician’s check beat guessing at a dose.
Related reading
About this article
This article was researched using NIH fact sheets, a WHO guideline, Cochrane and other systematic reviews, randomized trials, university releases and the discoverer’s own accounts, all listed below. It was reviewed in October 2026. It is general education, not medical, legal or financial advice.
Sources
- Prasad AS. “A Letter from Ananda S. Prasad, MD, PhD, to the APS Distinguished Physiologists.” The Physiologist Magazine, American Physiological Society, January 2020.
- Prasad AS. “History of the Discovery of Zinc Essentiality for Humans.” Trace Elements in Medicine (Mikroelementy v meditsine), 2010;11(1):1-6. journal.microelements.ru
- NIH Office of Dietary Supplements. “Zinc: Fact Sheet for Health Professionals.” NIH, updated January 6, 2026. ods.od.nih.gov
- “Zinc and Immunity: An Essential Interrelation.” Archives of Biochemistry and Biophysics, 2016 (DOI record). doi.org
- World Health Organization. “Guideline on Management of Pneumonia and Diarrhoea in Children Up to 10 Years of Age,” 2024: recommendations on zinc for acute watery and persistent diarrhoea and on zinc dose (via PAHO’s BIGG guideline database). bigg-rec.bvsalud.org and bigg-rec.bvsalud.org
- Guideline Central. “WHO Management of Pneumonia and Diarrhoea in Children Up to 10 Years of Age Guideline Summary.” Guideline dated December 31, 2024; page updated September 30, 2026. guidelinecentral.com
- Ali AA, Naqvi SK, Hasnain Z, et al. “Zinc Supplementation for Acute and Persistent Watery Diarrhoea in Children: A Systematic Review and Meta-Analysis.” Journal of Global Health, 2024;14:04212 (Aga Khan University record). scholars.aku.edu
- Lassi ZS, Moin A, Bhutta ZA. “Zinc Supplementation for the Prevention of Pneumonia in Children Aged 2 Months to 59 Months.” Cochrane Database of Systematic Reviews, December 4, 2016, CD005978.pub3. pubmed.ncbi.nlm.nih.gov
- Tufts University, via ScienceDaily. “Zinc May Reduce Pneumonia Risk in Nursing Home Elderly” (on Meydani SN, Barnett JB, Dallal GE, et al., “Serum Zinc and Pneumonia in Nursing Home Elderly,” American Journal of Clinical Nutrition, 2007;86:1167-1173). October 23, 2007. sciencedaily.com
- Thomas S, et al. “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 Network Open, 2021;4:e210369. pubmed.ncbi.nlm.nih.gov
- Ben Abdallah S, et al. (corresponding author Nouira S). “Twice-Daily Oral Zinc in the Treatment of Patients With Coronavirus Disease 2019: A Randomized Double-Blind Controlled Trial.” Clinical Infectious Diseases, 2023;76(2):185-191. academic.oup.com
- NIH Office of Dietary Supplements. “Zinc: Fact Sheet for Consumers.” NIH, updated October 4, 2022. ods.od.nih.gov
- Prasad AS. “Discovery of Human Zinc Deficiency: 50 Years Later.” Journal of Trace Elements in Medicine and Biology, 2012;26(2-3):66-69 (abstract record). nutrition-evidence.com
- NutraIngredients (trade press). “Zinc Effective for Managing Diarrhoea in Children, but Lower Doses May Be Needed to Reduce Vomiting – WHO.” March 11, 2025. nutraingredients.com
- Morgenstern J. “Is Zinc the Cure for COVID?” First10EM, February 20, 2023. first10em.com