Zinc

Overview

Zinc is the trace mineral that hundreds of enzymes need to do their work. The recommended intake is 8 mg a day for adult women and 11 mg for adult men, and the upper limit from all sources is 40 mg a day. The catch is copper: zinc taken at 50 mg or more for weeks can lower copper absorption, and a 2018 series of seven copper-deficient patients found that four had been using zinc-containing denture adhesive.

What is Zinc?

Key takeaways

• The recommended intake is 8 mg a day for adult women and 11 mg for adult men, and the upper limit from all sources is 40 mg a day (NIH ODS).
• The 2-capsule serving of NMN + NR with Resveratrol and TMG lists 10 mg zinc as bisglycinate chelate, one quarter of the adult upper limit (live product page).
• Zinc at 50 mg or more for weeks can lower copper absorption, which is why NIH sets the upper limit to protect copper status (NIH ODS).
• In a 2014 trial of 15 healthy adults taking 10 mg doses, zinc citrate and gluconate were each absorbed about 61% of the time, and zinc oxide about 50%.
• In a 2007 trial of 12 healthy women, a single 15 mg dose of zinc bisglycinate gave 43% higher serum zinc exposure than zinc gluconate.
• In a 12-week trial of adults aged 55 and older, a multivitamin with zinc raised blood zinc status but did not change immune function measures (Fantacone et al., 2020).
• No trial in our search tested zinc alone for NAD+ levels, healthy aging or lifespan.

What is zinc?

Zinc is a metal the body needs in small amounts. It circulates as an ion, Zn2+, and attaches to proteins, many of them enzymes. NIH ODS describes zinc as required for the catalytic activity of hundreds of enzymes, and as playing a role in immune function, protein and DNA synthesis, wound healing, cell signaling and cell division, and the sense of taste.

Food is the main route in. Meat, fish and other seafood, eggs and dairy are good sources, and oysters carry more zinc per serving than any other food (NIH ODS). Beans, nuts and whole grains contain zinc too, but their phytates bind it in the gut. Absorption from food runs from 5% to more than 50%, depending on how much plant food a diet contains (NIH ODS).

The body balances zinc through absorption from the diet, excretion into the gut and reabsorption (NIH ODS). As intake rises, the amount absorbed rises too, but the fraction absorbed falls. That shrinking fraction is why more zinc does not buy proportionally more absorption.

Form also matters before absorption. A chelate is a mineral bound to an amino acid or another molecule. Zinc bisglycinate binds zinc to glycine. A 2025 digestion model found it more soluble after digestion than zinc sulfate, 27% against 24% (Rock et al., 2025). That is a lab measure, not a blood level.

The copper link is the part most people have not heard of. NIH ODS says zinc at 50 mg or more, taken for weeks, can interfere with copper absorption, leading to low copper status, reduced immune function and lower HDL cholesterol. Case reports show what that looks like. In a 2018 series, seven patients with acquired copper deficiency had tingling and gait problems as their first symptoms, and four had used zinc-containing denture adhesive, with high serum and urinary zinc (Poujois et al., 2018). In a 2011 case report, a 58-year-old man developed copper deficiency myelopathy after heavy use of zinc-containing denture cream (Doherty et al., 2011). Copper replacement improved neurological symptoms in six of the seven 2018 patients, over a mean of two years.

How it works

Zinc works mostly as a cofactor, a helper that an enzyme needs before it can act. NIH ODS describes it as required for the catalytic activity of hundreds of enzymes. Those enzymes support protein and DNA synthesis, cell division and wound repair, which is why zinc sits underneath so much routine cell maintenance. These roles are established biochemistry, so they are the least contested part of the zinc story.

Absorption is the first gate. The fraction absorbed falls as intake rises, and phytates in the diet reduce it (NIH ODS). The form changes the result too. In a 2014 crossover of 15 healthy adults, 10 mg of zinc citrate and gluconate were absorbed about 61% of the time, and zinc oxide about 50%. The authors link oxide's lower absorption to its insolubility in water (Wegmüller et al., 2014).

Once absorbed, zinc is held in balance through absorption, excretion into the gut and reabsorption (NIH ODS). High intakes overwhelm that balance, and copper is the nutrient NIH uses to set the upper limit.

The exact steps by which zinc lowers copper absorption are not settled in the sources checked for this page. The outcome is documented, so this page reports the outcome and labels the mechanism as open.

Proposed mechanisms get less weight than the enzyme roles. The authors of the 2008 cold trial tied their symptom results to zinc's antioxidant and anti-inflammatory properties (Prasad et al., 2008). That is an interpretation, not a pathway the trial established.

The sections below grade what human trials show. Absorption by form and correction of low zinc status have the clearest data. Immune, cold and NAD+ outcomes are weaker.

Evidence at a glance

What the evidence doesn't support yet

Four claims outrun the data.

That extra zinc improves immune function in healthy adults. A 12-week multivitamin trial with zinc, in adults aged 55 and older, raised blood zinc status but left immune function tests unchanged (Fantacone et al., 2020). A 2024 trial of 59 healthy adults found no reduction in upper respiratory infection incidence or severity from a selenium, zinc and vitamin D combination started during illness (Haas et al., 2024). The immune health pillar covers the wider evidence.

That zinc shortens every cold. One 2008 trial found shorter colds with zinc acetate lozenges started early (Prasad et al., 2008). NIH ODS reads the wider lozenge and syrup trials as shortening colds without clearly reducing severity, and none of the cold trials in this search tested capsules. Quercetin pairings are covered in the quercetin monograph and the quercetin and zinc research article; this page does not repeat their claims.

That bisglycinate absorbs better than every other form. The one human trial compared it only with gluconate, in 12 women after a single 15 mg dose (Gandia et al., 2007). Animal data are mixed: rats on a phytate-heavy diet absorbed glycinate better than sulfate (Schlegel and Windisch, 2006), while sheep retained less zinc from glycinate in one experiment (Lee et al., 2022).

That zinc supports NAD+ levels, healthy aging or lifespan. No trial in this search tested zinc alone for these outcomes. The nearest human data are a 2026 cross-sectional NHANES analysis of 8,125 adults, which linked higher dietary zinc to lower accelerated-aging risk and which its authors describe as associations (Zhang et al., 2026), and a 2025 skin-aging study of a multi-ingredient supplement where zinc was one of several ingredients (Michelini et al., 2025). For the NAD+ pathway, see the NAD+ and longevity guide.

Clinical evidence

• Correcting zinc deficiency in nursing home residents: a randomized trial comparing 30 and 60 mg/day elemental zinc supplementation — Zinc-deficient nursing home residents, 26 to 35 per group, took 30 or 60 mg a day of elemental zinc or placebo for 12 months. Both doses raised serum zinc. Every 60 mg participant reached target by month 8, against 13 of 28 (46%) on 30 mg. No copper status change was detected. Limit: small groups, and not powered for clinical outcomes.
• Zinc absorption by young adults from supplemental zinc citrate is comparable with that from zinc gluconate and higher than from zinc oxide — 15 healthy adults took 10 mg of zinc as citrate, gluconate or oxide, without food, in a randomized three-way crossover with isotope tracing. Fractional absorption: citrate 61.3%, gluconate 60.9%, oxide 49.9%. Three participants absorbed little or none from oxide. Limit: single doses in 15 people, and no bisglycinate arm.
• A bioavailability study comparing two oral formulations containing zinc (Zn bis-glycinate vs. Zn gluconate) after a single administration to twelve healthy female volunteers — 12 healthy women took a single 15 mg dose of zinc bisglycinate or zinc gluconate in a randomized crossover with a 7-day washout. Bisglycinate raised oral bioavailability by 43.4% compared with gluconate, measured by serum zinc curves. Limit: 12 women, one dose, and one comparator salt.
• Individualized Supplementation of Immunoactive Micronutrients and Severity of Upper Respiratory Infection Symptoms: A Randomized Intervention Study — 59 healthy adults received a personalized supplement with or without selenium, zinc and vitamin D, started during acute illness. Incidence and severity of upper respiratory infection did not differ significantly between groups. Limit: a combination product, doses not given in the abstract, acute use only.
• The Effect of a Multivitamin and Mineral Supplement on Immune Function in Healthy Older Adults: A Double-Blind, Randomized, Controlled Trial — Healthy adults aged 55 and older took a multivitamin and mineral product or placebo daily for 12 weeks. Blood zinc status improved. Bacterial killing, neutrophil activity, cytokine and salivary IgA measures did not change. Limit: multinutrient product, so the zinc effect cannot be isolated; zinc dose not in the abstract.
• Duration and severity of symptoms and levels of plasma interleukin-1 receptor antagonist, soluble tumor necrosis factor receptor, and adhesion molecules in patients with common cold treated with zinc acetate — 50 adults with a new cold took a zinc acetate lozenge (13.3 mg zinc) or placebo every 2 to 3 hours while awake. Mean cold duration was 4.0 days with zinc against 7.1 with placebo, and symptom severity scores were lower. Limit: lozenges, not capsules; one trial, and the wider lozenge literature is mixed (NIH ODS).
• Neurological presentations revealing acquired copper deficiency: diagnosis features, aetiologies and evolution in seven patients — Seven patients with acquired copper deficiency and neurological symptoms, studied prospectively. Four had used zinc-containing denture adhesive, and serum and urinary zinc were high in four. Copper replacement improved neurological symptoms in six of seven over a mean of two years. Limit: seven patients; one had two causes recorded.
• Zinc-containing denture adhesive: a potential source of excess zinc resulting in copper deficiency myelopathy — Case report of a 58-year-old man with copper deficiency myelopathy, linked to overuse of zinc-containing denture cream. Limit: one patient, and the authors say the link is possible rather than proven.
• Bioavailability of zinc glycinate in comparison with zinc sulphate in the presence of dietary phytate in an animal model with Zn labelled rats — Zinc-labelled rats on a phytate-containing diet received zinc glycinate or sulfate. True absorption was 51% for glycinate and 44% for sulfate, and retention 33% against 25%. Limit: rats on a semi-synthetic diet, not people; one author affiliation is a commercial company.
• Effect of zinc sources and experimental conditions on zinc balance in growing wethers — Growing sheep were fed several zinc sources. In one experiment, zinc glycinate retained 1.5% of intake against 17.8% for zinc hydroxychloride and amino acid complex. Across three experiments the glycinate results were inconsistent. Limit: sheep, not people.
• The Antagonistic Influence of Phytic Acid on Zinc Absorption: A Comparison of Inorganic and Chelated Trace Mineral Sources — A standardized digestion model and intestinal cell lines compared zinc bisglycinate, zinc sulfate and zinc proteinate with and without phytic acid. Bisglycinate was 27% soluble after digestion against 24% for sulfate. Sulfate was affected from a phytic acid ratio of 2:100, the chelates only from 4:100. Limit: in vitro only; no measure of absorption in people.

Dosage & forms

• Zinc bisglycinate (this formula):
• Zinc gluconate:
• Zinc citrate:
• Zinc oxide:
• Zinc sulfate:
• Zinc acetate:

Safety & interactions

How much to take

The research used three doses. The 2007 single-dose trial gave 15 mg. The 2014 absorption trial gave 10 mg without food. The 2026 trial gave 30 or 60 mg a day for 12 months to participants who started below target, and only the 60 mg group reached target in every participant by month 8 (Gandia et al., 2007; Wegmüller et al., 2014; Ortega et al., 2026). The recommended intake for adults is 8 mg a day for women and 11 mg for men, rising to 11 and 12 mg in pregnancy and while nursing (NIH ODS).

The NMN + NR with Resveratrol and TMG serving provides 10 mg, one serving a day. That sits near the recommended intake for men, above it for women, and at a quarter of the 40 mg upper limit. Whether it fits your needs depends on your diet, your other zinc sources and any test results. We checked the label of this formula only and did not survey the zinc doses on other brands in this run.

Timing matters at the margin. The 2014 absorption figures come from doses taken without food. Phytates in beans, nuts and whole grains lower absorption (NIH ODS; Rock et al., 2025), so keeping zinc away from a phytate-heavy meal is one practical step. Keep zinc apart from iron of 25 mg or more taken at the same time (NIH ODS), and from quinolone and tetracycline antibiotics and penicillamine (see the table below). Pick a consistent time of day, because the label gives none.

How long before anything shows: the 2026 trial followed serum zinc for months, while single-dose trials track blood zinc over hours. Nothing in these sources shows a measurable change at 10 mg a day, and no trial has tested this formula.

Diminishing returns: fractional absorption falls as intake rises (NIH ODS). Above 40 mg a day from all sources, you are past the upper limit NIH set to protect copper status. The 2026 trial found 60 mg a day without adverse effects over a year, but that was a trial correction, not a standing dose for healthy adults.

Safety profile

At the doses in these trials, zinc was well tolerated in the short term, and the 2026 trial reported no adverse effects at 60 mg a day for 12 months (Ortega et al., 2026). High intakes are another matter. NIH ODS lists nausea, dizziness, headaches, stomach upset, vomiting and loss of appetite at high doses.

Side effects by frequency. Common at high intakes: nausea, stomach upset, headache and loss of appetite. Uncommon: low copper status after weeks at 50 mg or more. Rare: copper-deficiency nerve and blood problems, documented mainly in case series, including one linked to zinc-containing denture adhesive (Poujois et al., 2018; Doherty et al., 2011). NIH ODS does not give frequencies for the common effects, so these groupings are our reading of the sources.

Copper. The NIH upper limit exists because of copper. Zinc at 50 mg or more for weeks can lower copper absorption, reduce immune function and lower HDL cholesterol (NIH ODS). The 2026 trial at 60 mg for 12 months detected no copper change, so the effect is real at high intake and not certain at every dose.

Very high doses. NIH ODS notes that 142 mg a day of supplemental zinc may interfere with magnesium absorption and balance (see the magnesium monograph). That is far above any serving here.

Interactions with medicines

Evidence strength: the antibiotic and penicillamine timings come from NIH ODS and a 1995 review, the firmest interaction evidence here. The diuretic effect is a documented change in zinc loss, with no timing rule in these sources. The iron effect depends on dose and on whether the two are taken together.

Who should ask first

The product label asks anyone who is pregnant or nursing, or who takes medication, to ask a practitioner before use. Add people who take the medicines above, people who use zinc-containing denture adhesive (Doherty et al., 2011), and anyone whose clinician has prescribed zinc for a medical reason. NIH ODS says upper limits do not apply to zinc given for medical reasons, and that those people should be under a physician's care.

Upper limits and signs of too much

NIH ODS sets the adult upper limit at 40 mg a day from food and supplements combined. Short-term signs of too much zinc are nausea, dizziness, headache, stomach upset, vomiting and loss of appetite. Signs of low copper after long high intake include anemia, low white cell counts, tingling and unsteady walking (Poujois et al., 2018). Add up the elemental zinc from every product you take, and if the total passes 40 mg a day, talk to a clinician before you continue.

Buying guide

The dose that matches the research

Read the elemental zinc on the Supplement Facts panel, not the weight of the compound. The 2007 single-dose trial used 15 mg, the 2014 absorption trial used 10 mg, and the 2026 trial that started participants below target used 30 or 60 mg a day for a year (Gandia et al., 2007; Wegmüller et al., 2014; Ortega et al., 2026). For adults, the recommended intake is 8 mg a day for women and 11 mg for men (NIH ODS).

The NMN + NR with Resveratrol and TMG serving lists 10 mg of zinc as bisglycinate chelate per two capsules, one serving a day. Against the research above, that is a modest dose: inside the range used in absorption trials, close to the recommended intake, and well below the 30 to 60 mg used in the 2026 trial.

Any product that adds 30 mg a day or more, or stacks zinc from several products, needs a clinician's review.

The form that absorbs

Citrate and gluconate were absorbed about equally in the 2014 trial, 61% each. Oxide lagged at 50%, and three of the 15 people absorbed little or none (Wegmüller et al., 2014). Bisglycinate has one small human trial: 43% higher serum zinc exposure than gluconate after a single 15 mg dose in 12 women (Gandia et al., 2007). Digestion and rat data point the same way (Rock et al., 2025; Schlegel and Windisch, 2006), and one sheep study did not (Lee et al., 2022). That makes bisglycinate a reasonable form with thin human data. Ask any brand, including us, for the human trial behind its form.

Proof of testing

The live product page links a lot-specific certificate of analysis for this formula (lot 0077634 at the time of our check), and says the product is made and tested in Mt. Angel, Oregon, in a cGMP facility. Match the lot number on your bottle to a certificate, and check that the certificate reports zinc content, not just a pass line. The lab testing and certificates of analysis hub lists certificates by product and lot.

Fillers and other zinc sources

The live Supplement Facts panel lists a vegetarian capsule (hypromellose and water), organic brown rice and magnesium stearate, and no copper. Read the rest of any label the same way. Zinc can also come from multivitamins, some nasal sprays and some homeopathic products, and zinc-containing denture creams have been a documented source of excess (NIH ODS). Add those amounts before you judge the total.

Price per day

The live price is $59.99 for 30 servings, about $2.00 a day for the full formula (live product page). That buys six ingredients, so the zinc is not a per-day purchase on its own. For any zinc product, compare price per day with the elemental zinc per day, and compare forms only once you have the absorption data behind each. The NMN and NR buying guide covers the wider category.

Red flags

• Proprietary blends that hide the zinc amount.
• Claims that zinc supports a body system with no study named.
• More than 40 mg a day of zinc from all products combined, without a clinician's direction.
• Zinc oxide as the only zinc source, given the 50% absorption in the 2014 trial.

Bottom line

Add up the zinc from every product you take, and keep the total under 40 mg a day unless a clinician has set a higher target. If you think you need more, ask for a test rather than deciding from a label. The 10 mg in the NMN + NR serving is a modest, labeled amount, and it does not replace medical advice.

Related reading

• The history of iron supplements, from chlorosis to the ferritin test
• how high-dose beta-carotene raised lung cancer risk in smokers
• the eye trials that paired zinc with antioxidants

Frequently Asked Questions

What does zinc do in the body?

Zinc is required for the activity of hundreds of enzymes. NIH ODS also lists roles in immune function, protein and DNA synthesis, wound healing, cell signaling and cell division, and the sense of taste. Those roles are established biochemistry. Whether extra zinc changes any of them in a healthy adult who already has enough is a narrower question, and most of the human trials on it come back null or mixed.

How much zinc is too much for an adult?

The NIH upper limit for adults is 40 mg a day from food and supplements combined. Doses of 50 mg or more taken for weeks can lower copper absorption, and high intakes can cause nausea, dizziness, headaches, stomach upset, vomiting and loss of appetite. A 10 mg serving is a quarter of the limit. Add up zinc from every product you take, including multivitamins, before deciding you are under it.

What does zinc do to copper absorption?

Sustained high zinc intake can interfere with copper absorption, and NIH ODS puts the level at 50 mg or more for weeks. Case reports show what low copper looks like: anemia, low white cell counts, tingling and gait trouble. In a 2018 series of seven patients, four had used zinc-containing denture adhesive. A 2026 trial at 60 mg a day for 12 months detected no copper change, so the risk is real at high intake but not certain at every dose.

Why would a NAD+ formula include zinc?

The NMN + NR with Resveratrol and TMG serving lists 10 mg of zinc as bisglycinate chelate, and the product page describes zinc as helping hundreds of enzymes work, which matches NIH ODS. We found no human trial that tested zinc alongside [NMN](/ingredients/nmn-nicotinamide-mononucleotide) or [NR](/ingredients/nr-nicotinamide-riboside), so the pairing is a formulation choice, not a measured effect. At 10 mg, the zinc is a modest dose.

What forms of zinc are there and how do they differ?

Common forms include gluconate, citrate, sulfate, acetate, oxide and bisglycinate. In a 2014 trial of 15 adults taking 10 mg, citrate and gluconate were absorbed about equally at 61%, and oxide at 50%. Bisglycinate has one small human trial showing higher serum zinc than gluconate, and the animal and lab data mostly agree. Phytates in beans and whole grains lower absorption, and iron of 25 mg or more taken at the same time can reduce it.

Who should ask a clinician before taking zinc?

Ask first if you take quinolone or tetracycline antibiotics, penicillamine or thiazide diuretics, if you are pregnant or nursing, or if a clinician has prescribed zinc for a medical reason. Ask too if you use zinc-containing denture adhesive or take several zinc products. NIH ODS says the upper limits do not apply to zinc given for medical reasons, and that those people should be under a physician's care. The product label asks the same of anyone who is pregnant, nursing or taking medicine.

Do I need zinc at all?

Zinc is in meat, seafood, eggs, dairy, beans, nuts and whole grains (NIH ODS), so diet is the first place to look. Whether a supplement adds anything depends on your intake and your status. A blood test is an imperfect guide, because serum zinc shifts with the time of the draw, infection and other factors (NIH ODS). If you think you are short, ask a clinician about testing rather than deciding from a label.

Is 10 mg of zinc a lot?

It depends on who is asking. For adult men, 10 mg is about 91% of the recommended intake of 11 mg. For adult women, it is 125% of the recommended 8 mg. It is a quarter of the adult upper limit of 40 mg. The 2026 deficiency trial used 30 to 60 mg a day for a year, three to six times the amount in the serving.

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