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Zinc

Evidence Level
Very Strong
4 Clinical Trials
8 Documented Benefits
5/5 Evidence Score

Zinc, an essential trace mineral, is commonly supplemented in forms like zinc gluconate, acetate, or citrate, playing a critical role in immune function, protein synthesis, and cellular repair. It supports immune health by enhancing the activity of T-cells and natural killer cells, potentially reducing the duration and severity of colds when taken early. Zinc is vital for skin health, aiding wound healing and reducing inflammation in conditions like acne. It also contributes to DNA formation, enzyme function, and reproductive health, including testosterone production. Supplements typically provide 15–30 mg/day, but excessive intake (>40 mg/day) may cause side effects like nausea, diarrhea, or copper deficiency due to impaired absorption. Consult a healthcare provider for appropriate dosing, especially if on medications like antibiotics or with conditions like kidney disease, to avoid interactions or toxicity.

Studied Dose 8–11 mg/day (RDA); therapeutic: 25–40 mg/day elemental zinc; upper limit 40 mg/day; always pair with 1 mg copper per 15 mg supplemental zinc
Active Compound Zinc bisglycinate / Zinc picolinate (elemental Zn)
Deficiency information View details

Zinc deficiency affects an estimated 17% of the global population, with mild-to-moderate deficiency more common than overt cases. In the US, deficiency is most often seen in vegetarians, older adults, people with malabsorption, and those on long-term diuretics. Symptoms can be subtle and develop gradually.

Common symptoms

  • Frequent infections, slow wound healing
  • Hair loss or thinning
  • Skin issues — acne, eczema, dry rough skin
  • Loss of taste or smell
  • Loss of appetite
  • Diarrhea (in severe cases)
  • Eye and skin lesions (in severe cases)
  • Delayed growth and development in children
  • Hypogonadism, impotence, or delayed puberty
  • Difficulty concentrating, mental fog

At-risk groups

  • Vegetarians and vegans (plant zinc has lower bioavailability due to phytates)
  • Older adults (>60% may consume below the EAR)
  • Pregnant and breastfeeding women
  • Exclusively breastfed infants over 6 months without complementary feeding
  • People with GI conditions (Crohn's, ulcerative colitis, short bowel)
  • People with sickle cell disease
  • People with chronic kidney disease
  • People with alcohol use disorder
  • People taking long-term diuretics, ACE inhibitors, or penicillamine
When to see a doctor: Persistent slow wound healing combined with hair loss, recurrent infections, or loss of taste/smell warrants a zinc test (serum or plasma zinc, ideally fasting). Important: long-term zinc supplementation above 40 mg/day can cause copper deficiency — don't supplement at high doses without medical guidance.
Explore related deficiencies →
Sources: NIH ODS — Zinc Health Professional Fact Sheet · PMID 23914218 — Zinc deficiency clinical review

Benefits

Immune System Support

Zinc enhances immune function by aiding T-cell production and activation, potentially reducing the duration and severity of colds when taken early.

Supported by Trial 2, Trial 3

Wound Healing

Zinc promotes skin repair and collagen synthesis, accelerating wound healing and recovery from injuries or surgeries.

Supported by Trial 1, Trial 2

Protein Synthesis and Growth

Zinc is vital for protein synthesis, DNA formation, and cell division, supporting growth and development, particularly in children and pregnant women.

Supported by Trial 1, Trial 2

Antioxidant Properties

Zinc acts as an antioxidant, protecting cells from oxidative stress and reducing inflammation, which may lower chronic disease risk.

Supported by Trial 1, Trial 2

Hormonal Health

Zinc supports testosterone production and reproductive health in men and women, potentially improving fertility.

Supported by Trial 1, Trial 2

Skin Health

Zinc helps manage acne by regulating oil production and reducing inflammation, often used in topical treatments.

Supported by Trial 1, Trial 2

Cognitive Function

Zinc supports brain health, aiding memory, learning, and mood regulation through neurotransmitter function.

Supported by Trial 1, Trial 2

Taste and Smell

Zinc is essential for maintaining proper taste and smell senses by supporting related enzyme functions.

Supported by Trial 1, Trial 2

Mechanism of action

1

Immune System Support

Zinc enhances immune function by regulating T-cell development and activation, interacting with immune signaling pathways, and inhibiting viral replication, such as in rhinoviruses, by stabilizing cell membranes and blocking viral entry.

2

Wound Healing

Zinc promotes wound healing by supporting collagen synthesis and fibroblast proliferation, acting as a cofactor for enzymes like matrix metalloproteinases that facilitate tissue remodeling and repair.

3

Protein Synthesis and Growth

Zinc facilitates protein synthesis and growth by serving as a cofactor for over 300 enzymes, including those involved in DNA and RNA synthesis, stabilizing protein structures, and enabling cell division through zinc-finger protein interactions.

4

Antioxidant Properties

Zinc reduces oxidative stress by inducing metallothionein production, which scavenges free radicals, and by inhibiting NADPH oxidase, an enzyme that generates reactive oxygen species, thus protecting cells from damage.

5

Hormonal Health

Zinc regulates hormonal health by acting as a cofactor for enzymes in steroidogenesis, supporting testosterone synthesis, and modulating gonadotropin-releasing hormone activity to influence reproductive function.

6

Skin Health

Zinc controls skin health by regulating sebum production through inhibition of 5-alpha-reductase and reducing inflammation via suppression of pro-inflammatory cytokines like IL-6, aiding in acne management.

7

Cognitive Function

Zinc supports cognitive function by modulating NMDA and GABA receptors in the brain, facilitating synaptic plasticity, and maintaining neuronal signaling critical for memory, learning, and mood regulation.

8

Taste and Smell

Zinc enables taste and smell by acting as a cofactor for gustin (carbonic anhydrase VI), an enzyme essential for taste bud function and olfactory receptor signaling, ensuring sensory acuity.

Clinical trials

1
Zinc for Pediatric Asthma — Clinical Trial

Randomized, double-blind, placebo-controlled trial (NCT03171961) in zinc-deficient children with asthma exacerbations.

Zinc-deficient pediatric asthma patients.

Modest signals on asthma exacerbation outcomes in zinc-deficient subgroup. Note: pediatric asthma management primarily uses ICS, SABAs, biologics — zinc supplementation adjunctive at most in deficient populations.

2
Zinc for COVID-19 — Tunisia Clinical Trial (negative)

Randomized, double-blind, placebo-controlled trial (NCT05212480) in 470 COVID-19 patients receiving oral zinc vs placebo.

470 COVID-19 patients.

Primary endpoint negative: zinc did not reduce COVID-19 outcomes vs placebo. Important rigorous negative trial. Consistent with broader COVID supplement evidence — zinc, vitamin D, and other supplements did not show definitive treatment benefits in COVID despite enthusiastic early enthusiasm.

3
Zinc + Vitamin C for Common Cold — Clinical Trial (negative)

Clinical trial in 214 ambulatory adults with common cold receiving high-dose zinc (50 mg) and ascorbic acid (8 g) vs usual care. (JAMA Network Open)

214 cold patients.

Primary endpoint negative: no significant reduction in symptom duration (5.9 days zinc vs 6.7 days standard care, p=0.45). GI side effects more common with treatment. Important pragmatic negative trial — high-dose zinc/vitamin C for established cold is not supported.

4
Zinc for HIV Patients with Low Plasma Zinc — Clinical Trial

Randomized, controlled trial (NCT00149552) in 231 HIV-infected adults with low plasma zinc receiving zinc supplementation.

231 HIV patients with zinc deficiency.

Zinc supplementation delayed immunological failure (CD4 <200 cells/mm³) and reduced diarrhea incidence vs control in zinc-deficient HIV patients. Note: HIV management primarily uses ART; zinc adjunctive in deficient populations.

Side effects and drug interactions

Common Potential side effects

Nausea and Gastrointestinal Discomfort: High doses of zinc, typically above 40 mg/day, can cause nausea, vomiting, diarrhea, or stomach cramps due to irritation of the gastrointestinal tract.
Metallic Taste: Excessive zinc intake, especially from supplements, may lead to a persistent metallic taste in the mouth, likely due to its interaction with salivary proteins.
Reduced Copper Absorption: Chronic high zinc intake can interfere with copper absorption by inducing metallothionein in the intestines, which binds copper and reduces its bioavailability, potentially leading to copper deficiency.
Immune Suppression: Prolonged excessive zinc intake (e.g., &gt;100 mg/day) may paradoxically suppress immune function by disrupting the balance of immune cell activity, including T-cell responses.
Headache and Dizziness: Some individuals report headaches or dizziness with high zinc doses, possibly due to altered electrolyte balance or nervous system effects.
Lowered HDL Cholesterol: Long-term high zinc supplementation may reduce HDL ("good") cholesterol levels, potentially increasing cardiovascular risk, though the mechanism is not fully understood.
Allergic Reactions: Rarely, zinc supplements may cause allergic reactions, such as rash or itching, likely due to hypersensitivity to zinc compounds or supplement additives.

Important Drug interactions

Drug Interactions: Zinc can reduce the absorption or efficacy of certain medications, such as antibiotics (e.g., tetracyclines, quinolones) or penicillamine, by forming complexes that limit their bioavailability.

Featured in these supplement guides

Acne→Bone Density→Eczema & Skin Inflammation→Eye Health→Fertility→Hair Loss→Immune Support→Inflammation→Liver Health→Low Testosterone→Mouth & Gum Health→Skin Health & Anti-Aging→Thyroid Support→

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Frequently asked questions about Zinc

How much zinc should I take?

The RDA is 8 to 11 mg per day, and most supplements provide 15 to 30 mg. Avoid taking more than about 40 mg per day long-term without medical advice, since chronic high zinc can cause copper deficiency.

Should I take zinc with food?

Zinc absorbs well on an empty stomach but can cause nausea that way, so taking it with a little food is gentler and still effective. Avoid taking it at the same time as high-calcium or high-iron supplements, coffee, or whole-grain meals, which reduce absorption.

Does zinc help with colds?

Zinc started within about 24 hours of the first symptoms may modestly shorten a cold, with lozenges that dissolve in the mouth being the studied form. It works best as a short course at onset, not as a daily megadose.

What is the best form of zinc?

Well-absorbed chelated forms like zinc picolinate, bisglycinate, or citrate are good, gentle choices. Zinc gluconate is common and effective, including in lozenges. Zinc oxide is the least absorbable. For everyday use, a chelated form at 15 to 30 mg is a solid pick.

What is Zinc?

Zinc, an essential trace mineral, is commonly supplemented in forms like zinc gluconate, acetate, or citrate, playing a critical role in immune function, protein synthesis, and cellular repair.

What is Zinc used for?

Zinc is researched primarily for Immune Support, Hair, Skin & Nails, and Men's Health. Zinc enhances immune function by aiding T-cell production and activation, potentially reducing the duration and severity of colds when taken early.

What are the signs of Zinc deficiency?

Zinc deficiency affects an estimated 17% of the global population, with mild-to-moderate deficiency more common than overt cases. In the US, deficiency is most often seen in vegetarians, older adults, people with malabsorption, and those on long-term diuretics. Symptoms can be subtle and develop gradually.

What is the recommended dosage of Zinc?

The clinically studied dose is 8–11 mg/day (RDA); therapeutic: 25–40 mg/day elemental zinc; upper limit 40 mg/day; always pair with 1 mg copper per 15 mg supplemental zinc Always follow the product label and check with a healthcare provider for personal advice.

Is Zinc safe, and does it have side effects?

For most healthy adults, Zinc is well tolerated at studied doses. Reported effects can include: Nausea and Gastrointestinal Discomfort: High doses of zinc, typically above 40 mg/day, can cause nausea, vomiting, diarrhea, or stomach cramps due to irritation of the gastrointestinal tract. It may also interact with some medications. Zinc is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Zinc interact with any medications?

Possible interactions include: Drug Interactions: Zinc can reduce the absorption or efficacy of certain medications, such as antibiotics (e.g., tetracyclines, quinolones) or penicillamine, by forming complexes that limit their bioavailability. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Zinc?

NutraSmarts rates the evidence for Zinc as Very Strong (5 out of 5). It is backed by 4 clinical trials and 4 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(4 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Rerksuppaphol S, Rerksuppaphol L. Zinc supplementation in children with asthma exacerbations. Pediatr Rep. 2016;8(4):6685. doi: 10.4081/pr.2016.6685.PubMedUsed to support: Pediatric asthma RCT — 42 zinc-deficient children with acute asthma exacerbation; oral zinc syrup 50 mg/day for 1 week as adjunct to standard treatment improved clinical asthma scores compared to placebo
  2. Ben Abdallah S, Mhalla Y, Trabelsi I, Sekma A, Youssef R, Bel Haj Ali K, Ben Soltane H, Yacoubi H, Msolli MA, Stambouli N, Beltaief K, Grissa MH, Khrouf M, Boukef R, Boubaker H, Bouida W, Nouira S. Twice-daily oral zinc in the treatment of patients with coronavirus disease 2019: a randomized double-blind controlled trial. Clin Infect Dis. 2023;76(2):185-191. doi: 10.1093/cid/ciac807.PubMedUsed to support: COVID-19 RCT — 470 COVID-19 patients in Tunisia (NCT05212480); twice-daily oral zinc gluconate vs placebo, evaluating ICU admission, mortality, and hospital length of stay as outcomes
  3. Thomas S, Patel D, Bittel B, Wolski K, Wang Q, Kumar A, Il'Giovine ZJ, Mehra R, McWilliams C, Nissen SE, Desai MY. 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 Netw Open. 2021;4(2):e210369. doi: 10.1001/jamanetworkopen.2021.0369.PubMedUsed to support: Outpatient respiratory infection RCT — 214 ambulatory adults with confirmed SARS-CoV-2; high-dose zinc gluconate (50 mg), ascorbic acid (8000 mg), or both did not significantly reduce symptom duration vs usual care, and GI side effects were more common with treatment
  4. Baum MK, Lai S, Sales S, Page JB, Campa A. Randomized, controlled clinical trial of zinc supplementation to prevent immunological failure in HIV-infected adults. Clin Infect Dis. 2010;50(12):1653-60. doi: 10.1086/652864.PubMedUsed to support: HIV immunological outcomes RCT — 231 HIV-infected adults with low plasma zinc (NCT00149552); zinc supplementation for 18 months delayed immunological failure (CD4 drop below 200) by 4-fold and reduced diarrhea incidence vs placebo