A reference work, not a recommendation to use: this profile describes mechanism and evidence and does not replace medical advice. The claims come from marketing and forums and are tested here, not endorsed.

Claims checked

  • Testosterone ↑

    Only proven in patients

    Testosterone & hormones · healthy · Human, non-randomised

    In trained men with adequate supply, testosterone remained unchanged under a zinc-containing product [6]; a systematic review did not rate zinc as an effective testosterone booster [8]. A rise was seen only in zinc deficiency: in a double-blind study of men on hemodialysis [5] and, uncontrolled, in older men with mild deficiency [4].

  • Libido and potency ↑

    Only proven in patients

    Libido & sexual function · Patients: zinc deficiency (hemodialysis, postmenopausal women with low zinc levels) · Human, randomised

    In 20 men on hemodialysis, potency and libido improved under zinc, not under placebo [5]. In 116 postmenopausal women with low zinc levels and impaired sexual function, the sexual function index improved in an RCT [12]. For people without deficiency, data are lacking.

  • Better sperm quality and fertility

    No benefit

    Pregnancy & fertility · Patients: men from couples undergoing fertility treatment · Human, randomised

    In a large RCT with 2370 men, folic acid and zinc changed neither sperm concentration, motility, morphology nor live birth rate; DNA fragmentation rose slightly, gastrointestinal complaints were more frequent [9].

  • Fewer and shorter colds

    Mixed results

    Immune system & infections · healthy · Human, randomised

    Cochrane review of 34 RCTs with 8526 participants: for prevention, probably little or no effect; for treatment, possibly a shorter duration (on average 2.4 days) in very heterogeneous studies and with low certainty; more non-serious side effects [10].

Mechanism of action

Evidence map: Zinc

Each line stands for a published finding; line style and color show where it comes from. The filter hides weaker evidence levels. Sources: see references.

Zinc is involved in more than 300 enzymatic reactions, in gene regulation and in immune functions [1]. It is absorbed in the small intestine and bound to metallothionein in the enterocytes; when the zinc supply rises, more metallothionein is formed, which binds copper even more tightly than zinc. In this way, an excess of zinc inhibits copper absorption, which is used therapeutically in Wilson disease [1]. How well zinc is absorbed depends on the compound (fasting about the same from citrate and gluconate, less from oxide [2]; for picolinate only a small, older study with status markers [3]); the comparisons of forms are in the form profiles (see the profiles “Zinc citrate,” “Zinc gluconate,” “Zinc oxide” and “Zinc picolinate”).

The main promise concerns testosterone. In healthy men, the zinc content of blood cells correlated with serum testosterone; experimental zinc restriction markedly lowered testosterone in four young men, and in nine older men with mild zinc deficiency it rose with zinc supplementation, in each case without a control group [4]. In a double-blind study of 20 men on hemodialysis, testosterone and sperm count rose under zinc, LH and FSH fell, and potency and libido improved [5]. In 14 trained men with adequate zinc intake, however, a zinc-containing combination product (ZMA) did not change testosterone [6]. A systematic review of 8 clinical and 30 animal studies concludes that the effect depends on the baseline status [7], and in a review of so-called testosterone boosters, zinc was not among the substances rated as effective [8].

For fertility and infections, too, the large studies are sobering. In an RCT with 2370 men from couples undergoing fertility treatment, folic acid and zinc improved neither sperm quality nor live birth rate; sperm DNA fragmentation rose slightly [9]. A Cochrane review of 34 RCTs found no protection against colds and, in treatment, at most a shorter duration with low certainty, but more side effects [10]. Too much zinc causes anemia and neutropenia via copper deficiency, which are often first misdiagnosed as myelodysplastic syndrome [11]. For loss of smell after zinc gel in the nose, see the profile “Zinc gluconate.”

Targets

TargetTypeActionKey dataEvidence
Metallothionein in the enterocyteOtherExpression ↑binds copper more tightly than zinc Laboratory[1]
Gonadal axis (testosterone, LH, FSH)Hormone axisActivatoronly in zinc deficiency Human, randomised[4][5][7]
Zinc-dependent enzymes (more than 300 reactions)EnzymeBinding Laboratory[1]

Effect profile

Which signaling systems the compound affects according to current data. ↑ enhanced, ↓ dampened, ≈ modulated, ○ no effect; dots = evidence level.

  • Dopamineno data
  • Noradrenalineno data
  • Serotoninno data
  • Acetylcholineno data
  • Glutamate · AMPAno data
  • Glutamate · NMDAno data
  • GABAno data
  • Histamineno data
  • Orexinno data
  • Adenosineno data
  • Opioidsno data
  • Melatoninno data
  • Neurotrophinsno data
  • Blood flowno data
  • Nitric oxideno data
  • Energy metabolismno data
  • Insulin · glucoseno data
  • Inflammation · oxidativemodulated · Involvement in immune functions according to a review; clinical benefit against colds uncertain[1][10]
  • Stress axisno data
  • Testosterone axis↑ · In zinc deficiency (dialysis, mild deficiency), testosterone rose, LH and FSH fell; with adequate supply, no rise[4][5][6]
  • Endocannabinoidsno data
  • Autophagy · senescenceno data
  • Immune systemno data
  • Lipid metabolismno data
  • Coagulation · fibrinolysisno data
  • Methylationno data

Routes of administration and bioavailability

How much of a compound reaches the blood or target tissue depends on the route into the body and on the dosage form. All routes of administration explained

  • Oral (swallowed) · various zinc compounds

    ≈ 61% (citrate, gluconate), ≈ 50% (oxide); fasting, human

    Randomized, double-blind crossover study using the double isotope method in 15 adults [2]. Further comparisons of forms, also for picolinate and bisglycinate, are in the form profiles.

    Human, randomised

  • Buccal (inner cheek) · Lozenges (acetate, gluconate, orotate)

    Half of the cold studies in the Cochrane review used lozenges, most often with gluconate [10].

    Human, randomised

Human studies

  • Zinc status and testosterone

    cross-sectional plus two uncontrolled interventions · healthy (40 men; 4 young men with zinc restriction; 9 older men with mild deficiency) · n = 53 · 20 weeks of restriction and 3–6 months of zinc supplementation, respectively

    Measured: Serum testosterone

    Result: Correlation of cellular zinc and testosterone; restriction lowered testosterone, zinc supplementation in deficiency raised it.[4]

    Human, non-randomised

  • Men on hemodialysis

    double-blind, placebo-controlled · Patients: hemodialysis with zinc deficiency · n = 20 · 6 months

    Measured: Plasma zinc, testosterone, LH, FSH, sperm count, sexual function

    Result: Testosterone and sperm count rose, LH and FSH fell, potency and libido better; no change under placebo.[5]

    Human, randomised

  • ZMA with adequate zinc intake

    small intervention study (randomization not described in the abstract) · healthy (trained men, 22–33 years) · n = 14 · not given in the abstract

    Measured: Total and free testosterone, steroid metabolites in urine

    Result: Serum zinc rose, testosterone and metabolite pattern unchanged.[6]

    Human, non-randomised

  • Folic acid and zinc in fertility treatment (FAZST)

    RCT, multicenter, placebo-controlled · Patients: men from couples undergoing fertility treatment · n = 2370 · 6 months

    Measured: Live birth, sperm quality

    Result: Live birth 34% vs. 35%, sperm parameters unchanged, DNA fragmentation +2.4 percentage points.[9]

    Human, randomised

  • Cochrane review colds

    systematic review of 34 RCTs · Children and adults · n = 8526 · varied

    Measured: Cold risk, duration, side effects

    Result: Prevention hardly effective (RR 0.93); treatment possibly −2.37 days (low certainty); more side effects (RR 1.34).[10]

    Human, randomised

  • Postmenopausal women with low zinc

    RCT · Patients: postmenopausal women with low serum zinc and impaired sexual function · n = 116 · not given in the abstract

    Measured: Testosterone, Female Sexual Function Index

    Result: Sexual function improved; testosterone rise according to the conclusion (abstract incomplete at this point).[12]

    Human, randomised

  • Zinc-induced blood count damage

    systematic review of case reports · Patients: zinc excess · n = 37 · Exposure weeks to years

    Measured: Anemia, neutropenia, copper level

    Result: Copper lowered in all; recovery mostly after discontinuation and copper supplementation, neurological damage partly permanent.[11]

    Human, non-randomised

Risks and warnings

  • Copper deficiency from zinc excess

    Persistently high zinc intake inhibits copper absorption via metallothionein [1]. A systematic review of 37 cases found lowered copper in all, almost always anemia, often neutropenia up to pancytopenia; bone marrow findings were frequently misdiagnosed as myelodysplastic syndrome. The blood count mostly recovered, neurological damage partly only incompletely [11]. Sources were food supplements, zinc-containing denture adhesive creams and swallowed coins [11].

    Human, non-randomised

  • Gastrointestinal complaints

    Abdominal pain, nausea and vomiting were more frequent under folic acid and zinc than under placebo [9]; in cold treatment, more non-serious side effects occurred, such as an unpleasant taste [10].

    Human, randomised

  • Sperm DNA

    In the FAZST study, sperm DNA fragmentation rose slightly under folic acid and zinc; whether zinc alone is responsible is left open by the combination design [9].

    Human, randomised

Interactions

  • Copper: Zinc inhibits copper absorption in the gut via induced metallothionein [1]; clinically relevant with persistently high intake [11].
  • Phytate (grains, legumes): Phytate reduces zinc absorption and thereby raises the requirement [1].

Fact check: common claims

  • partly supported

    “Zinc raises testosterone levels”

    Shown only in zinc deficiency, for example in men on hemodialysis [5] or with mild deficiency [4]; with adequate supply, no rise [6].

  • not supported

    “ZMA is a natural testosterone booster for athletes”

    In the only study found in trained men with adequate zinc intake, total and free testosterone remained unchanged [6].

  • refuted

    “Zinc improves male fertility”

    For men undergoing fertility treatment without known deficiency, a large RCT showed no benefit for sperm or live births [9]; zinc was tested together with folic acid.

  • partly supported

    “Zinc lozenges shorten colds”

    Possibly a shorter duration, but very heterogeneous studies and low certainty; for prevention hardly any effect [10].

  • refuted

    “With zinc, more is better”

    Persistently high intake can cause copper deficiency with anemia, neutropenia and nerve damage [1][11].

Pharmacokinetics

Absorption
In the small intestine; fractional absorption fasting ≈ 61% from citrate and gluconate, ≈ 50% from oxide [2]. Phytate in food lowers absorption [1].
Half-life
Not verified.
Metabolism
No breakdown (element); storage and regulation in the enterocytes via metallothionein [1].
Entry into the brain
Not verified.

Legal status

Germany
Not verified (widespread as a food supplement in Germany; legal basis not checked in the register).
EU
Zinc is listed in Annex I of Directive 2002/46/EC; Annex II Part B names 16 zinc compounds authorized as a zinc source in food supplements, including all forms with their own profile [13]. EFSA has set a tolerable upper intake level for zinc [1].
USA
US authorities have set an upper intake level for zinc [1]; otherwise not verified.
Other countries
Therapeutically, zinc is used in Wilson disease to block copper absorption in the gut [1].

Authorised EU health claims

EU claim authorised An authorised health claim is a legal statement about the nutrient, not about this form, and not a level of evidence. The evidence for this form is reported separately under the main claim and in the human studies.

  • “Zinc contributes to the maintenance of normal testosterone levels in the blood”

    Nutrient
    Zinc
    Legal basis
    Regulation (EU) No 432/2012[14]
    Reading
    legally permitted; in healthy people with adequate supply, no rise found, see the promise “Testosterone ↑”

  • “Zinc contributes to normal fertility and reproduction”

    Nutrient
    Zinc
    Legal basis
    Regulation (EU) No 432/2012[14]
    Reading
    legally permitted; in men undergoing fertility treatment no benefit (together with folic acid), see the promise “Better sperm quality and fertility”

  • “Zinc contributes to the normal function of the immune system”

    Nutrient
    Zinc
    Legal basis
    Regulation (EU) No 432/2012[14]
    Reading
    legally permitted; for colds, see the promise “Fewer and shorter colds”

Related compounds

Borsame class (German only)Kupferantagonist (German only)
antagonist
demonstrably inhibits the uptake or action of this substance, or vice versa (evidence in the text)

Open questions

  • From which zinc status do men benefit hormonally, and how can mild deficiency be measured reliably?
  • Are there randomized studies with testosterone as the endpoint in healthy people without deficiency that go beyond combination products?
  • Do organic zinc compounds such as picolinate or bisglycinate really differ from citrate or gluconate in modern isotope studies?

References

  1. Schoofs H, Schmit J, Rink L. Zinc toxicity: understanding the limits. Molecules. 2024;29(13):3130. doi:10.3390/molecules29133130 · PubMed
  2. Wegmüller R, Tay F, Zeder C, Brnic M, Hurrell RF. Zinc absorption by young adults from supplemental zinc citrate is comparable with that from zinc gluconate and higher than from zinc oxide. J Nutr. 2014;144(2):132–6. doi:10.3945/jn.113.181487 · PubMed
  3. Barrie SA, Wright JV, Pizzorno JE, Kutter E, Barron PC. Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans. Agents Actions. 1987;21(1-2):223–8. doi:10.1007/BF01974946 · PubMed
  4. Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ. Zinc status and serum testosterone levels of healthy adults. Nutrition. 1996;12(5):344–8. doi:10.1016/s0899-9007(96)80058-x · PubMed
  5. Mahajan SK, Abbasi AA, Prasad AS, Rabbani P, Briggs WA, McDonald FD. Effect of oral zinc therapy on gonadal function in hemodialysis patients. A double-blind study. Ann Intern Med. 1982;97(3):357–61. doi:10.7326/0003-4819-97-3-357 · PubMed
  6. Koehler K, Parr MK, Geyer H, Mester J, Schänzer W. Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement. Eur J Clin Nutr. 2009;63(1):65–70. doi:10.1038/sj.ejcn.1602899 · PubMed
  7. Te L, Liu J, Ma J, Wang S. Correlation between serum zinc and testosterone: a systematic review. J Trace Elem Med Biol. 2023;76:127124. doi:10.1016/j.jtemb.2022.127124 · PubMed
  8. Morgado A, Tsampoukas G, Sokolakis I, Schoentgen N, Urkmez A, Sarikaya S. Do “testosterone boosters” really increase serum total testosterone? A systematic review. Int J Impot Res. 2024;36(4):348–64. doi:10.1038/s41443-023-00763-9 · PubMed
  9. Schisterman EF, Sjaarda LA, Clemons T, Carrell DT, Perkins NJ, Johnstone E, et al. Effect of folic acid and zinc supplementation in men on semen quality and live birth among couples undergoing infertility treatment: a randomized clinical trial. JAMA. 2020;323(1):35–48. doi:10.1001/jama.2019.18714 · PubMed
  10. Nault D, Machingo TA, Shipper AG, Antiporta DA, Hamel C, Nourouzpour S, et al. Zinc for prevention and treatment of the common cold. Cochrane Database Syst Rev. 2024;5(5):CD014914. doi:10.1002/14651858.CD014914.pub2 · PubMed
  11. Dutta A, Chaudhary V, Kumari S, Rohita, Sharma KK, Pal B. Zinc-induced hematologic toxicities: a systematic review of descriptive studies. Biol Trace Elem Res. 2026;204(9):6628–42. doi:10.1007/s12011-026-05136-z · PubMed
  12. Mazaheri Nia L, Iravani M, Abedi P, Cheraghian B. Effect of zinc on testosterone levels and sexual function of postmenopausal women: a randomized controlled trial. J Sex Marital Ther. 2021;47(8):804–13. doi:10.1080/0092623X.2021.1957732 · PubMed
  13. Richtlinie 2002/46/EG des Europäischen Parlaments und des Rates vom 10. Juni 2002 zur Angleichung der Rechtsvorschriften der Mitgliedstaaten über Nahrungsergänzungsmittel. ABl. L 183 vom 12.7.2002, S. 51. Konsolidierte Fassung vom 26.11.2025 (CELEX 02002L0046-20251126).
  14. Verordnung (EU) Nr. 432/2012 der Kommission vom 16. Mai 2012 zur Festlegung einer Liste zulässiger anderer gesundheitsbezogener Angaben über Lebensmittel als Angaben über die Reduzierung eines Krankheitsrisikos sowie die Entwicklung und die Gesundheit von Kindern. ABl. L 136 vom 25.5.2012, S. 1 (CELEX 32012R0432).
How this profile was checked

Last reviewed: 2026-10-24. All sources with a DOI or PMID were resolved automatically via Crossref or doi.org and PubMed.

Translated from the German profile (version of 2026-10-24); translation checked on 2026-10-26.

Checked

  • All DOIs resolved via Crossref and PMIDs via PubMed by checking script.
  • Checked against the abstracts: 61.3%, 60.9%, 49.9%, three people without absorption from oxide, n = 15 [2]; picolinate, n = 15 [3]; r = 0.43, restriction n = 4, zinc supplementation n = 9 [4]; n = 20, testosterone and sperm ↑, LH and FSH ↓, potency and libido [5]; n = 14, testosterone unchanged [6]; 8 clinical and 30 animal studies [7]; list of effective boosters without zinc [8]; n = 2370, live birth 34% vs. 35%, DNA fragmentation +2.4 percentage points [9]; 34 RCTs, 8526 participants, RR 0.93, MD −2.37 days, RR 1.34 for side effects [10]; 37 cases, copper always lowered [11]; n = 116 [12].
  • In the full text: metallothionein mechanism, Wilson disease, phytate, existence of EFSA and US upper intake levels [1].
  • PubChem: zinc, CID 23994.
  • Annex I and Annex II Part B of Directive 2002/46/EC, consolidated version CELEX 02002L0046-20251126 (Cellar, XHTML, October 24, 2026): zinc in Annex I; 16 zinc compounds in Annex II Part B (acetate, L-ascorbate, L-aspartate, bisglycinate, chloride, citrate, gluconate, lactate, L-lysinate, malate, mono-L-methionine sulfate, oxide, carbonate, L-pidolate, picolinate, sulfate) [13].
  • Regulation (EU) No 432/2012: wording of the entered claims checked in the base version (CELEX 32012R0432, Cellar, XHTML) and unchanged in the consolidated version of August 20, 2025 (CELEX 02012R0432-20250820, Cellar, XHTML) on October 24, 2026. Claims on testosterone, fertility and the immune system [14].

Not verified

  • Legal status in Germany and the US (register not checked); the EU status is documented via Annex II [13].
  • The testosterone values in [5] are given in the abstract with inconsistent units (ng/dl and ng/ml, respectively) and were therefore not included as numbers.
  • Randomization and duration of the ZMA study [6] and the duration of the RCT [12] are not described in the abstract; the abstract of [12] is incomplete for the testosterone result.
  • The upper intake levels themselves are not stated as numbers, in line with the guideline.

No dosages, no sources of supply. This information does not replace medical advice.

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