Zinc

Zinc is an essential trace mineral that every cell in your body uses. It is part of enzymes in all six enzyme classes, and it helps hold the shape of about 2,500 human proteins that control genes. EFSA and the NIH say it supports growth, immune defense, wound healing and the sense of taste. EFSA is the EU’s food safety agency, and the NIH is the US National Institutes of Health.

An adult body holds only about 1.5 g of zinc in women and 2.5 g in men. About 85% of it sits in muscle and bone.

Most readers do not know that the body has no real zinc store. EFSA says zinc has no major storage site, so the body depends on a steady supply from food. For many people that supply falls short.

A modeling study estimates that 17.3% of the world’s people are at risk of inadequate zinc intake, mostly where diets rest on cereals and beans. These foods contain phytate, a plant compound that binds zinc.

In wealthy countries the questions are different: cold lozenges, vegetarian diets, supplements and taking too much. The evidence is uneven. Zinc clearly helps children with diarrhea where deficiency is common, and a zinc and antioxidant formula slows one eye disease.

Trials of zinc for colds disagree, though, and 50 mg a day or more for weeks can interfere with copper. This page sets out what the studies show.

Health benefits of zinc

• ★★★EU allows 18 health claims for zincThey cover normal immune function, thinking, fertility, bones, skin, hair and nails. The claims describe normal body function, not the treatment of disease.
• ★★★Less diarrhea in children given zincAs treatment, zinc supplements shortened diarrhea by about 11 hours in children over 6 months (low-certainty evidence). As daily prevention, they cut cases by 9% but not deaths, and vomiting was more common.
• ★★Slower late-stage macular degeneration, with antioxidant pillsIn people with signs of age-related macular degeneration, a daily antioxidant, zinc (80 mg) and copper pill gave 0.72 times the odds of advanced disease. Across 26 trials, zinc alone against placebo in 5 studies gave 0.83 times the odds (moderate-certainty evidence).
• ★★Colds may be about 2 days shorterIn 19 treatment trials, zinc lozenges, syrups, tablets or nose products shortened colds by 2.37 days, but results varied greatly and certainty was low. In 7 lozenge trials using over 75 mg a day, colds were 33% shorter.
• ★★Zinc with folic acid: no more live birthsMen in couples planning infertility treatment took 30 mg of zinc with 5 mg of folic acid daily for 6 months. Live births were 34% against 35% on placebo, and sperm DNA damage was slightly higher on the supplement (29.7% against 27.2%).

Foods high in zinc

Oysters lead every USDA ranking on this page. A 3 oz (85 g) serving holds 14.1 mg, or 128% of the 11 mg Daily Value (the FDA’s label target). 100 g holds 16.6 mg. Per serving, ground beef (4.72 mg in 4 oz) and adzuki beans (4.07 mg per cup) come next, then ground lamb and hemp seeds.

Pumpkin seeds, often named as a zinc source, give 2.21 mg per ounce. Per 100 g, the next foods after oysters are hemp seeds (9.9 mg), pumpkin seeds (7.81 mg) and sesame seeds (7.75 mg). That is why seeds rank higher by weight than by serving.

Oyster values vary a lot. The NIH lists 32 mg in 3 oz of raw farmed Eastern oysters and 28.2 mg in cooked Pacific oysters, more than our ranking shows.

The NIH also notes that beef supplies 20% of the zinc Americans eat, because it is eaten so often. It lists roasted sirloin at 3.8 mg in 3 oz and cheddar at 1.5 mg in 1.5 oz. Boiled lentils have 1.3 mg in half a cup.

Zinc from plant foods is absorbed less well because of phytate. Absorption from food ranges from 5% to more than 50%, depending on how much plant food a diet holds. The NIH suggests soaking beans, grains and seeds for several hours before cooking, and notes that organic acids in fermented foods may help.

How zinc works

Most of the biochemistry below is well established. But it comes from reviews, EFSA’s modeling of human absorption studies, and cell and animal work, not from trials of extra zinc in people.

Five ideas cover most of it. Zinc is built into enzymes and gene-controlling proteins, the gut tightly controls how much gets in, and phytate in plant foods holds it back. Immune cells depend on it, and too much blocks copper. Here is each one, and what has been seen in people.

It is built into enzymes and gene-controlling proteins

EFSA describes three jobs for zinc: catalytic (speeding up reactions), structural and regulatory. It has a structural or catalytic role in each of the six classes of enzymes. Still, a direct link between a sign of deficiency and one specific enzyme has not been confirmed in people.

Zinc fingers are protein folds that need zinc to work, and the human transcriptome holds about 2,500 of them. Zinc also adjusts signaling inside cells, in particular through kinase and phosphorylase activity. That is why the EU can authorize such different claims. They range from normal DNA synthesis and normal metabolism of vitamin A to protection of cells from oxidative stress (see antioxidants).

The gut controls how much gets in

Most zinc is absorbed in the upper small intestine. Transporters called ZIP carry zinc into cells and ZnT carry it out, and the gut turns their genes up or down in response to intake. Absorption follows saturation kinetics: the more zinc you swallow, the more is absorbed, but the share falls. One review puts the maximum absorption in adults at about 6 mg a day.

With a low-phytate, low-zinc diet (under 4 mg a day), the absorbed share can reach 60% or more. In an isotope trial, fasting adults absorbed about 61% of a 10 mg supplement dose. The gut also adjusts how much of the body’s own zinc it sheds into the stool. One review calls this of major importance in setting zinc requirements.

Phytate in plant foods holds zinc back

Phytate, the storage form of phosphorus in seeds, grains and beans, binds zinc in the gut into a complex the body cannot absorb. It is the main dietary factor known to cut zinc absorption. One review estimated that the average requirement doubles at 1,000 mg of phytate a day.

EFSA turned this into numbers. For an adult woman, its recommended intake rises from 7.5 mg a day at 300 mg of phytate to 12.7 mg at 1,200 mg. For a man, it rises from 9.4 to 16.3 mg. In a trial of fortified wheat foods, adults absorbed 13.8% of zinc from low-phytate bread and 6.4% from higher-phytate porridge.

EFSA notes that germinating or fermenting grains reduces the effect of phytate. Iron supplements of 25 mg or more taken at the same time can also lower zinc absorption, the NIH says. The iron added to fortified food does not.

Immune cells depend on it

EFSA points out that the immune system is especially vulnerable to deficiency. That is partly because immune cells divide quickly and partly because many of their signaling steps need zinc. A review of zinc in infection describes poorer cell-mediated immunity in deficiency, and a role for zinc in controlling the inflammatory switch NF-κB.

The idea behind cold lozenges is that zinc may stop rhinovirus (a common cold virus) binding and replicating in the nose and throat. It may also calm inflammation. Researchers have hypothesized this, the NIH says.

In people, the evidence is mixed. A year of 45 mg a day lowered infections in 50 older adults, while the Cochrane review found little effect on preventing colds.

Too much zinc blocks copper

Long-term high doses of zinc interfere with copper uptake, and many toxic effects of zinc are really copper deficiency, one review concludes. In perfused rat intestine, very high zinc in the gut reduced copper in the intestinal cells and the copper passed on to the blood. High-zinc diets also raised the copper bound to metallothionein, a protein that binds metals.

In people, case reports describe anemia, low white blood cells and nerve damage after months or years of high zinc from supplements or denture cream. The NIH says 50 mg or more for weeks can lower copper status, and the US and EU upper levels are set on that effect.

What has been seen in people

The clearest results are about deficiency, and about children where it is common. In malnourished children with diarrhea, zinc shortened it by about 26 hours. Giving zinc to children cut diarrhea cases by 9% without changing deaths. In older people at risk of macular degeneration, the AREDS tablet of antioxidants, zinc and copper cut the odds of advanced disease to 0.72 times.

Elsewhere the results are weaker, and colds are uncertain. Trials of zinc with folic acid for male fertility, and of zinc in pregnancy and for leg ulcers, found little or nothing. Two COVID-19 trials pointed in opposite directions. All of these are among the study cards above.

How much zinc do you need?

Adult men need 11 mg of zinc a day and adult women 8 mg, according to the US Recommended Dietary Allowance (RDA). The RDA is the daily amount that covers nearly all healthy people. The EU range is 9.4 to 16.3 mg for men and 7.5 to 12.7 mg for women, depending on how much phytate the diet holds.

Needs rise in pregnancy and breastfeeding. For women 19 and older, the US values are 11 mg in pregnancy and 12 mg while breastfeeding. For ages 14 to 18, they are 12 and 13 mg. EFSA adds 1.6 mg and 2.9 mg to the adult woman’s value.

Older adults have the same targets. The US allowance does not change after age 70, and EFSA found no zinc balance data beyond age 52, so it applies the adult basis. The NIH says older adults might have marginal intakes. In survey data from 2005 to 2016, 15% of US adults 19 and older ate less than the average requirement.

Zinc deficiency: signs and who is at risk

Severe deficiency is rare in wealthy countries, but marginal status is not. In infants and children, diarrhea is a common sign. In older children, hair loss, delayed growth and frequent infections become more common.

In the inherited form (acrodermatitis enteropathica), EFSA describes skin lesions around the body openings and the limbs, diarrhea, and loss of appetite and taste. In older adults, deficiency can delay wound healing and change thinking and mood, the NIH says.

• Digestive disease and bariatric surgery. About 15% to 40% of people with inflammatory bowel disease have zinc deficiency. About 50% of people newly diagnosed with celiac disease are at high risk of inadequacy or deficiency.
• Vegetarians and vegans. Phytate in beans and whole grains binds zinc, and a meta-analysis found serum zinc 0.93 µmol/L lower in vegetarians.
• Pregnancy, breastfeeding and infants. Needs rise. Breast milk alone does not meet an infant’s zinc need after 6 months, because milk zinc falls by about 75% by month nine.
• Sickle cell disease and alcohol use disorder. Children with sickle cell disease have a high risk of zinc insufficiency, possibly because of the chelation therapy used for iron overload. Low zinc status has been seen in 30% to 50% of people with alcohol use disorder.

Doctors usually test serum or plasma zinc (zinc in the liquid part of blood), which is normally 80 to 120 mcg/dL. Levels below 70 mcg/dL in women and 74 mcg/dL in men are taken to show inadequate zinc status.

The test has limits. It varies with the time of day and with infection, and it does not track intake well, so clinicians also weigh symptoms and risk factors. In US survey data from 2011 to 2014, some people aged 10 and older fell below the cutoff for their age and sex. That was 8.6% of males and 8.2% of females.

Forms of zinc: absorption and effects

Zinc supplements come as different compounds, and the label lists elemental zinc (the zinc itself), not the weight of the whole compound, the NIH notes. By weight, a gluconate tablet holds far less zinc than one of zinc oxide: 14% against 80%. That figure comes from a review whose authors work for a supplement maker. Forms also differ in solubility and taste.

Oxide does not dissolve in water, while acetate, gluconate and sulfate do. Acetate and sulfate taste bitter and astringent enough to cause vomiting in syrups, unless the taste is masked. The same review says the WHO recommends water-soluble forms for children’s diarrhea tablets and syrups.

The honest bottom line is that head-to-head evidence is thin. The best-controlled trial used isotope tracers in 15 adults and found citrate and gluconate equally absorbed, with oxide somewhat less. Claims that picolinate or bisglycinate are better rest on a few small studies that measured blood, hair or urine levels.

We found no trial that tested any form for a health outcome such as colds or diarrhea. So popular claims that one form works better for immunity or other outcomes have no trial behind them. Zinc from supplements has not been shown to be absorbed differently from zinc in meals that lack inhibitors such as phytate.

The forms used in the main outcome trials on this page were:

• AREDS (macular degeneration). Zinc oxide, 80 mg, with 2 mg of copper as cupric oxide.
• Cold trials. Lozenges of gluconate (9 of 17 lozenge trials in the Cochrane review), acetate (5) or both (2). Other trials used syrups, tablets and nose products.
• Other trials above. Gluconate in the older-adult infection trial and the outpatient COVID-19 trial, and acetate in the hospital COVID-19 trial. Sulfate, mostly as syrup, in the child prevention trials and the leg ulcer trials. The diarrhea trials used acetate, gluconate or sulfate. The fertility trial’s abstract does not name the form.

Form	Share of zinc by weight	What studies show	Source
Zinc gluconate	14%	Absorbed about as well as citrate by fasting adults (60.9% of a 10 mg dose). Used in most cold lozenge trials. Raised plasma zinc less than glycinate in one 6-week trial of 30 women.	1, 2, 4, 11
Zinc acetate	30%	In a pooled analysis, three acetate lozenge trials shortened colds by 40%; the gap from gluconate (28%) was not significant. We found no absorption comparison with other forms.	2, 3
Zinc citrate	31%	Absorption matched gluconate (61.3% versus 60.9%) in 15 fasting adults. At 50 mg a day for 4 weeks, it did not raise hair, urine or red-cell zinc.	1, 2, 6
Zinc sulfate	23%	Water-soluble and bitter. Absorbed from fortified flour about as well as oxide. Used as syrup in most child prevention trials.	2, 5, 13
Zinc oxide	80%	Does not dissolve in water. Absorption was 49.9% against 60.9% for gluconate when fasting, and 3 of 15 people absorbed little or none. A 12-man crossover also favored gluconate, with unequal doses. In fortified flour it matched sulfate. AREDS used it at 80 mg.	1, 2, 5, 7, 14
Zinc picolinate	21%	In one 15-person crossover at 50 mg a day, only picolinate raised hair, urine and red-cell zinc. Serum zinc did not change significantly. We found no other human comparison.	2, 6
Zinc glycinate (bisglycinate)	25%	Two small studies: 43.4% more zinc exposure than gluconate after one 15 mg dose in 12 women, and higher plasma zinc after 6 weeks of 60 mg in 30 women. Health outcomes were not tested.	2, 4, 8

Lozenges raise a formulation question of their own. To act on a cold, zinc has to be released in the mouth as free zinc ions. A saliva test found that citric acid in a gluconate lozenge suppressed free zinc ions. So did a large excess of mannitol plus sorbitol, while glycine did not.

The authors proposed this explains some negative cold trials, which is a hypothesis. A later meta-analysis of seven lozenge trials found that acetate and gluconate lozenges both shortened colds, with no clear difference between them. Side effects such as nausea and a bad taste were common in the trials above.

Is zinc safe? Supplements, dose and interactions

Zinc from food is not a concern for most people: the NIH notes that food rarely supplies 50 mg. For adults, the US tolerable upper intake level is 40 mg a day from food and supplements, set on copper status.

It is 34 mg for ages 14 to 18 and 23 mg for ages 9 to 13. It is 12 mg for ages 4 to 8 and 7 mg for ages 1 to 3. The same 40 and 34 mg apply in pregnancy and breastfeeding. It does not apply to people given zinc as treatment under a doctor’s care.

EFSA’s 2014 opinion describes an EU upper level of 25 mg a day for adults. The Scientific Committee on Food set it from a no-effect level of 50 mg and a safety factor of 2.

• Doses and side effects. High intakes can cause nausea, dizziness, headaches, stomach upset, vomiting and loss of appetite. In cold trials, non-serious side effects were more common with zinc (1.34 times the risk). And 80% of people sucking gluconate lozenges in a trial reported a bad taste, against 30% on placebo. Lozenge trials used 45 to 276 mg a day, well above the 40 mg upper level, for days to weeks. They were short courses, not long-term use.
• Copper deficiency. Doses of 50 mg or more for weeks can interfere with copper and lower HDL (“good”) cholesterol, the NIH says. Case reports describe anemia, low white blood cells and nerve damage after months to years of excess zinc. That includes denture cream that held about 17,000 to 34,000 µg of zinc per gram. The NIH says many denture creams have been reformulated without zinc.
• Nasal zinc and smell. By 2009 the FDA had received more than 130 reports of loss of smell with one homeopathic nasal zinc product. It judged that using the product as labeled would give significant daily exposure to nasal zinc. In June 2009 the agency advised consumers to stop using three of that maker’s nasal products. Case reports describe loss of smell that is long lasting or permanent.
• Prostate cancer. In a cohort of 46,974 men, more than 100 mg of supplemental zinc a day went with 2.29 times the risk of advanced prostate cancer. It is observational, and up to 100 mg a day was not linked to risk.
• Medicines. Quinolone and tetracycline antibiotics can bind zinc in the gut. The NIH advises taking the antibiotic at least 2 hours before or 4 to 6 hours after zinc. In 12 men, a multivitamin with zinc cut the ciprofloxacin exposure from 14.5 to 11.3 µg·h/ml. The zinc part was not separated out. In 7 volunteers, 45 mg of zinc as sulfate cut tetracycline absorption by about 30% but did not clearly change doxycycline. Take penicillamine and zinc at least 1 hour apart. Thiazide diuretics (water pills) such as hydrochlorothiazide raise zinc loss in urine: total excretion rose by 60% in 9 patients. Ask your doctor or pharmacist if you take any of these medicines.

How to get more zinc

• Best food. Oysters give 14.1 mg in 3 oz, 128% of the Daily Value, and pumpkin seeds give 2.21 mg per ounce. Beef, seeds, beans and dairy add up over a day.
• Soak and ferment plant foods. Phytate holds back zinc from beans, grains and seeds. Soaking them for several hours, or eating them fermented, helps. Absorption from low-phytate bread was 13.8%, against 6.4% from higher-phytate porridge.
• Food first, supplements for a reason. Vegetarians and vegans can look at fortified foods or low-dose supplements. If you take a supplement, stay under 40 mg a day unless a doctor says otherwise. In the best-controlled trial, citrate and gluconate were absorbed alike and oxide somewhat less.

History of zinc

A 2013 review dates the first discovery of human zinc deficiency to an Iranian man in 1961. That year Prasad and colleagues published on a syndrome of iron deficiency anemia, enlarged liver and spleen, underdeveloped sex glands, dwarfism and clay eating. Prasad later wrote that zinc deficiency causes growth retardation and underdeveloped sex glands, among other effects. He added that the high phytate content of cereal proteins in the developing world lowers the zinc available for absorption.

In 1974 a letter in The Lancet named acrodermatitis enteropathica, a skin and bowel disease of infants, as a lethal inherited zinc-deficiency disorder. EFSA now describes it as the result of genetic defects in zinc transporters in the gut and the mammary gland. It responds strongly to zinc treatment and is typically fatal without it.

The modern evidence base is more recent. The AREDS trial reported in 2001, and the EU listed its zinc health claims in Regulation 432/2012. EFSA set European reference values in 2014, and Cochrane updated its review of zinc for childhood diarrhea in 2016.

Frequently asked questions about zinc

How much zinc per day for a woman?

Adult women need 8 mg a day in the US, rising to 11 mg in pregnancy and 12 mg while breastfeeding (ages 19 and older). EFSA gives 7.5 to 12.7 mg for adult women, depending on phytate intake. It adds 1.6 mg in pregnancy and 2.9 mg while breastfeeding. The US upper level is 40 mg a day from food and supplements.

Do zinc lozenges work for colds?

Possibly, but the trials disagree. A Cochrane review of 34 trials found that zinc used for treatment may shorten a cold by about 2.37 days, with low certainty. It did little to prevent colds (0.93 times the risk). Side effects were more common, and in one trial 80% of users reported a bad taste. Lozenge doses of 45 to 276 mg a day are far above the 40 mg upper level, so they are for short courses only.

What are the signs of too much zinc?

Short-term, high intakes can cause nausea, dizziness, headaches, stomach upset and vomiting. Doses of 50 mg or more for weeks can interfere with copper, which in case reports led to anemia, low white blood cells and nerve damage. Nasal zinc products have been linked to loss of smell, which can be permanent.

Do vegetarians need more zinc?

They may. Phytate in beans and whole grains binds zinc. In a meta-analysis, vegetarians had 0.88 mg less zinc intake and lower serum zinc. EFSA’s target for adult women rises from 7.5 mg to 12.7 mg as phytate intake goes from 300 to 1,200 mg a day. Soaking, sprouting and fermenting plant foods, fortified foods and low-dose supplements can help.

Which foods are highest in zinc?

Oysters lead our USDA ranking, with 14.1 mg in 3 oz and 16.6 mg per 100 g. Ground beef (4.72 mg in 4 oz), adzuki beans (4.07 mg per cup), ground lamb and hemp seeds follow per serving. Per 100 g, hemp seeds, pumpkin seeds (7.81 mg) and sesame seeds rank next. The NIH lists cheddar at 1.5 mg in 1.5 oz and boiled lentils at 1.3 mg in half a cup.

Does zinc improve immunity?

It does when a person is low in zinc. Deficiency harms immune cells, and zinc shortened diarrhea in malnourished children by about 26 hours. The EU also authorizes a claim for normal immune function. In people with enough zinc the evidence is thin. One trial in 50 older adults found fewer infections on 45 mg a day, but the Cochrane review found little effect on preventing colds.

What is the best form of zinc supplement?

No form has been shown to work better for health. In 15 fasting adults, citrate and gluconate were absorbed equally (about 61%) and oxide somewhat less (50%). Picolinate and bisglycinate looked better in a few small studies of blood, hair or urine levels, but no trial tested health outcomes. Look at the elemental zinc on the label, since gluconate is 14% zinc by weight and oxide 80%.

Does zinc help macular degeneration or male fertility?

For macular degeneration, only the AREDS combination has trial support. Antioxidants plus 80 mg of zinc and 2 mg of copper lowered the odds of advanced disease (0.72 times the odds) in people at risk. AREDS2 saw no apparent difference with a lower zinc dose. For male fertility, a trial of 2,370 men found that folic acid plus zinc did not raise live births (34% against 35%). Ask an eye doctor before using an AREDS-type supplement.