Zinc
Zinc is an essential trace mineral the body uses as a co-factor in over 300 enzymes — including those involved in immune function, DNA synthesis, protein synthesis, and wound healing. UK NHS reference intakes are 9.5 mg/day for men and 7 mg/day for women. Most UK adults meet these intakes from food; intakes are more likely to fall short in vegetarians, vegans, older adults, and others with reduced intake or absorption — the groups where a standard-dose supplement is most often used.
Camden Medicals editorial · Last reviewed 12 June 2026 · Next review June 2027
- Cross-checked against
- NHS
- NICE
- BNF
- EFSA
- FSA
Camden's editorial team independently graded each health claim below on the strength of the published evidence — see the grade beside every condition.
- Class
- Mineral
- NHS daily RNI
- 9.5 mg ♂ · 7 mg ♀
- Typical supplemental
- 10-25 mg/day in supplemental form for general use
- Top use evidence
- Strong
On this page
What it is
Zinc is a metallic chemical element (Zn, atomic number 30) that the body holds as the divalent Zn²⁺ ion. The body contains roughly 2–3 g of zinc in total, mostly in muscle, bone, skin, and the prostate. Unlike iron, the body has no large storage pool, which is why dietary adequacy matters week-to-week.
UK food sources include red meat, shellfish (oysters are the richest natural source), poultry, dairy, beans, nuts, wholegrain cereals, and seeds. Plant-source zinc is less well absorbed because phytates in wholegrains and pulses bind zinc in the gut — vegetarians and vegans typically need a slightly higher intake to achieve the same status.
In supplements, zinc is sold as zinc gluconate, zinc citrate, zinc sulfate, zinc picolinate, and zinc bisglycinate (also called zinc glycinate) for general supplementation. Zinc acetate appears almost exclusively in cold-shortening lozenges — its mechanism in lozenges (binding to ICAM-1 in the throat) is different from oral capsule supplementation. Zinc picolinate and bisglycinate are commonly marketed as superior absorption forms; head-to-head bioavailability data is mixed and the practical difference at nutritional doses is small.
At a glance
- UK NHS RNI: 9.5 mg/day (men), 7 mg/day (women). NHS upper limit 25 mg/day from supplements.
- Cofactor for >300 enzymes; required for immune function, DNA and protein synthesis, normal cognition, fertility, skin, and bone.
- Common UK supplemental forms: gluconate, citrate, sulfate, picolinate, bisglycinate; acetate is the lozenge form for cold-shortening, not for routine supplementation.
- Chronic intake above ~40 mg/day can cause copper deficiency, anaemia, and neurological symptoms — more is not better.
What people use it for
UK vegetarians and vegans
Plant-source zinc is less well absorbed because phytates in wholegrains, pulses, nuts, and seeds bind zinc in the gut. Vegetarians and vegans typically need a slightly higher intake to reach the same zinc status as omnivores. Soaking, sprouting, and fermenting (e.g. sourdough) reduce phytate and improve absorption. [1,3]
StrongOlder adults (65+)
Mild zinc inadequacy is common in older adults due to reduced food intake and reduced absorption. The GB-authorised claim is that zinc contributes to the normal function of the immune system; the NHS also lists making new cells and enzymes, processing carbohydrate, fat and protein, and wound healing among the jobs zinc does in the body. Routine megadosing is not appropriate — the NHS advises no more than 25 mg/day from supplements unless a doctor advises otherwise. [1,2,3]
ModeratePeople prone to frequent colds
Meta-analyses of zinc lozenges (zinc acetate or zinc gluconate) started within 24 hours of cold-symptom onset suggest a modest reduction in cold duration in adults. The evidence is for the lozenge formulation, not oral capsules; the most commonly cited Cochrane review on this topic was withdrawn in 2015 over methodological concerns, so Hemilä 2017 is the more current source. [5]
Some evidenceLimitedPeople with mild-moderate inflammatory acne
Some randomised trials suggest oral zinc (typically zinc gluconate or sulfate) modestly reduces inflammatory acne lesion counts versus placebo, though effect sizes are smaller than first-line topical or oral antibiotic options. NICE guideline NG198 does not list oral zinc as a recommended treatment for acne. If acne is affecting your day-to-day, see your GP or pharmacist — there are evidence-based options. [13,9]
Some evidenceLimitedAdults at intermediate-stage age-related macular degeneration (AMD)
The AREDS and AREDS2 trials found that a specific antioxidant + zinc combination (80 mg zinc oxide in the original AREDS, lowered to 25 mg in AREDS2) reduced 5-year progression to advanced AMD in adults with intermediate AMD — in the original trial, roughly 28 in 100 people on placebo progressed over five years compared with roughly 20 in 100 taking the formula. This is a clinically supervised use — discuss with your optometrist or ophthalmologist; do not self-prescribe AREDS-dose zinc. [7,6]
Some evidenceLimited
How it works
Zinc is a structural and catalytic co-factor for over 300 human enzymes and binds to "zinc-finger" motifs in transcription factors, which is why zinc adequacy is required for normal DNA synthesis, cell division, immune-cell function, and tissue repair.
Common myths
Myth"Zinc is a cold cure"
RealityZinc is not a cold cure. The lozenge evidence (Hemilä 2017) suggests roughly a one-third shortening of cold duration when zinc acetate or zinc gluconate lozenges are started within 24 hours of symptom onset — typically a 1–2 day reduction, not a cure. Started later than 24 hours, the effect is smaller or absent. Oral capsule supplementation does not have the same evidence base. [5]
Myth"More zinc means stronger immunity"
RealityThe GB-authorised claim is that zinc "contributes to the normal function of the immune system" — adequacy supports normal function. Supplementation above adequacy has not been shown to produce supra-normal immunity. Chronic intake above ~40 mg/day can drive copper deficiency, anaemia, and (with longer-term excess) neurological symptoms. The NHS upper limit is 25 mg/day from supplements unless advised otherwise. [2,1]
Myth"All zinc forms are interchangeable"
RealityMost zinc forms (gluconate, citrate, sulfate, picolinate, bisglycinate, acetate) are reasonably well absorbed and equivalent at nutritional doses. Two practical exceptions: zinc acetate lozenges are dosed locally at the throat to reduce cold duration — that mechanism is different from oral capsule absorption — and zinc oxide, while widely sold for general supplementation, is somewhat less well absorbed than the chelated forms in the same fasting conditions. Read the elemental-zinc figure on the label, not just the compound mass. [3]
Myth"Zinc treats COVID-19"
RealityThe COVID A to Z randomised trial (Thomas 2021, JAMA Network Open) found that high-dose zinc gluconate, ascorbic acid, or both did not significantly reduce symptom duration in ambulatory SARS-CoV-2 infection compared with usual care. The trial was stopped early for futility. There is no GB-authorised health claim for zinc and COVID-19. Marketing that conflated cold evidence with COVID outcomes was widely flagged by the ASA in 2020–2021. [14]
Common online questions
Synthesised from the questions UK shoppers most often ask online about Zinc. Each answer is editorial and links to its evidence in the Sources list below.
Lozenge or capsule — which type of zinc shortens a cold?
The cold-shortening evidence is for lozenges, not capsules. Hemilä 2017 pooled 7 trials of zinc acetate or zinc gluconate lozenges and found that lozenges started within 24 hours of cold-symptom onset shortened cold duration by roughly a third. Typical doses in the trials were 13–25 mg of elemental zinc per lozenge taken every 2–3 hours during waking hours, for no more than around 7 days. Oral zinc capsules taken at supplement doses do not have the same evidence base for cold-shortening — the lozenge mechanism is local, in the throat. Lozenges commonly cause a metallic taste and mild nausea; speak to a pharmacist if you take any prescription medicines before starting. [5]
Why is more zinc not better?
Zinc and copper compete for the same intestinal transporter. Chronic intake above ~40 mg/day from supplements can drive copper deficiency, which leads to a particular pattern of anaemia and, less commonly, neurological symptoms (myelopathy and peripheral neuropathy). The NHS sets the upper limit at 25 mg/day from supplements unless advised otherwise by a doctor; AREDS-dose zinc (25–80 mg) is paired with 2 mg copper specifically to prevent this. Over-the-counter "megadose" zinc immune products are the most common source of accidental long-term excess. [1,3]
Should I take zinc to prevent colds?
For prevention, the evidence is much weaker than for shortening an established cold. Daily preventive zinc has not been shown to meaningfully reduce the frequency of colds in healthy adults. The lozenge evidence is for treatment within 24 hours of symptom onset. The simplest position: keep dietary zinc adequate year-round; consider lozenges only when a cold begins. [5]
Is zinc picolinate or bisglycinate worth the extra money?
Zinc picolinate and zinc bisglycinate (sometimes labelled glycinate) are often marketed as superior absorption forms. Head-to-head bioavailability data is mixed and the practical difference at nutritional doses (RNI to 25 mg) is small. For most adults the form matters less than the elemental zinc dose printed on the label and whether you take it with food. Zinc sulfate and zinc oxide (the cheapest forms) are well absorbed in fasting adults; gluconate, citrate, and bisglycinate are often gentler on the stomach. [3]
Can I take zinc with iron, calcium, or my multivitamin?
High-dose zinc and high-dose iron compete for absorption when taken together at the same time, and high-dose calcium can also reduce zinc absorption. At nutritional doses inside a balanced multivitamin (each at 100% NRV or thereabouts) the interference is small and not usually a practical problem. If you are taking a clinical-strength dose of any one of them — for example a prescribed iron supplement for iron-deficiency anaemia — separate it from zinc by 2 hours. [3]
Does zinc help with hair loss?
There is no GB-authorised health claim linking zinc to hair growth or to treatment of hair loss. Severe zinc deficiency can cause hair loss as one symptom, and correcting that deficiency improves hair regrowth — but supplementation above adequacy in replete adults is not evidence-based for hair loss. If you are losing hair, see your GP or pharmacist; thyroid disease, iron deficiency, and androgenetic alopecia are common, treatable causes that need different interventions. [2]
When should zinc be separated from medicines?
Zinc binds to several common antibiotics in the gut and reduces their absorption. The BNF advises separating zinc from quinolone antibiotics (e.g. ciprofloxacin) and tetracycline antibiotics (e.g. doxycycline) by at least 2 hours, and from penicillamine by at least 2 hours. Zinc can also reduce absorption of levothyroxine — separate by at least 4 hours. Always tell your pharmacist what supplements you are taking when starting a new prescription. [8]
⚖️ The official position
What may lawfully be claimed about Zinc in Great Britain. This is a regulatory position, not an evidence grade.
A health claim is authorised in Great Britain.
“Zinc contributes to normal cognitive function”
“Zinc contributes to the normal function of the immune system”
“Zinc contributes to normal protein synthesis”
“Zinc contributes to normal DNA synthesis”
“Zinc contributes to the maintenance of normal testosterone levels in the blood”
“Zinc contributes to normal fertility and reproduction”
“Zinc contributes to normal acid-base metabolism”
“Zinc contributes to normal carbohydrate metabolism”
This claim is authorised for use in Great Britain under the GB Nutrition and Health Claims regulation. A product may carry it when it provides at least 15% of the UK NRV per recommended daily portion.
Authorised UK health claims
Verbatim from the GB Nutrition and Health Claims Register (Reg 432/2012 as assimilated in GB). A product can carry these claims when it provides at least 15% of the UK NRV per recommended daily portion.
8 authorised claims — show / hide
- "Zinc contributes to normal cognitive function"
- "Zinc contributes to the normal function of the immune system"
- "Zinc contributes to normal protein synthesis"
- "Zinc contributes to normal DNA synthesis"
- "Zinc contributes to the maintenance of normal testosterone levels in the blood"
- "Zinc contributes to normal fertility and reproduction"
- "Zinc contributes to normal acid-base metabolism"
- "Zinc contributes to normal carbohydrate metabolism"
🔬 Camden’s evidence review
The research Camden reviewed, graded on its strength. This is our own appraisal — it sits beneath the official guidance above, never above it.
Common cold — duration when zinc lozenges are started within 24h of onset
LimitedEvidencelimitedUK guidance leads: the NHS does not list zinc as a treatment for the common cold, and there is no GB-authorised health claim linking zinc to colds. Beneath that, the research Camden reviewed: the Hemilä 2017 meta-analysis of 7 randomised trials (575 participants) of zinc acetate or zinc gluconate lozenges reported that lozenges shortened cold duration by approximately one-third when started within 24 hours of symptom onset. The most-cited Singh & Das Cochrane review (2013, CD001364) drew similar conclusions, but the 2015 update was withdrawn, primarily over data-calculation concerns raised in the editorial assessment, and remains withdrawn. The trials studied lozenges, not oral capsules; the lozenge evidence does not transfer to capsule supplementation. [5,15,16]
Zinc-deficiency-related immune dysfunction
StrongEvidencestrongUK guidance leads: the GB Nutrition and Health Claims register authorises the claim that zinc contributes to the normal function of the immune system, and the NHS lists immune support among zinc's roles in the body. Beneath that, the research Camden reviewed: zinc deficiency impairs T-cell function, neutrophil activity, and antibody response, and correcting deficiency restores normal immune function — which is what the authorised claim describes. Supplementation above adequacy in already-replete adults has not been shown to push immunity above normal. [2,3]
Acne vulgaris — oral zinc
LimitedEvidencelimitedUK guidance leads: NICE NG198 (acne vulgaris management) sets the first-line options as fixed-combination topical regimens (for example topical adapalene with benzoyl peroxide) with oral lymecycline or doxycycline added for moderate-to-severe acne; it does not list oral zinc among the recommended treatments. The British Association of Dermatologists similarly notes there is not enough evidence to support specific treatments outside the standard pathway. Beneath that, the research Camden reviewed: Yee et al. 2020 (systematic review and meta-analysis) found that people with acne tended to have lower serum zinc and that oral zinc produced a modest reduction in inflammatory lesion counts versus placebo — a smaller effect than the first-line options. [13,9]
Age-related macular degeneration (AMD) progression — intermediate-stage
StrongEvidencestrongUK guidance leads: NICE NG82 (age-related macular degeneration) lists a diet low in vitamins, carotenoids and minerals among the AMD risk factors and frames AMD as a condition managed within specialist eye services; AREDS-type supplementation is an ophthalmology-supervised decision, not a self-care step, and there is no GB-authorised claim for zinc and eye disease. Beneath that, the research Camden reviewed: AREDS (2001) found that the antioxidant-plus-zinc formula reduced 5-year progression to advanced AMD in intermediate-stage disease (roughly 20 in 100 on the formula versus 28 in 100 on placebo), and AREDS2 (2013) showed that lowering zinc to 25 mg and swapping beta-carotene for lutein and zeaxanthin kept the benefit with a better safety profile. [7,6,10]
Wound healing
LimitedEvidencelimitedUK guidance leads: the NHS lists wound healing among the everyday jobs zinc does in the body, which is the basis for adequacy rather than for high-dose treatment; there is no GB-authorised claim for zinc accelerating wound healing beyond normal. Beneath that, the research Camden reviewed: adequate zinc is required for collagen synthesis, cell proliferation, and re-epithelialisation, and correcting deficiency improves wound-healing outcomes — but supplementation above adequacy in already-replete adults has not been shown to speed healing. NIH ODS describes the evidence as supportive in deficient patients only. [1,3]
COVID-19 (ambulatory) — zinc + ascorbic acid
InsufficientEvidenceinsufficientUK guidance leads: no NHS, NICE, or GB-authorised position supports zinc for COVID-19, and there is no authorised health claim linking zinc to COVID-19 outcomes. Beneath that, the research Camden reviewed: the Thomas et al. 2021 COVID A to Z trial randomly assigned 214 ambulatory adults with SARS-CoV-2 infection to high-dose zinc gluconate, ascorbic acid, both, or usual care; neither agent (alone or combined) significantly reduced symptom duration, and the trial was stopped early for futility. [14]
Safety
Zinc is generally well tolerated at intakes near the UK Reference Nutrient Intake (9.5 mg men, 7 mg women) and at typical supplemental doses up to 25 mg/day. Higher doses commonly cause stomach upset; chronic intake above ~40 mg/day can cause copper deficiency.
Talk to your pharmacist or GP first if you:
- You have haemochromatosis or another iron-overload condition (zinc affects copper metabolism).
- You have Wilson's disease — zinc IS used therapeutically in this condition, but only under specialist supervision; do not self-supplement.
- You take quinolone antibiotics (ciprofloxacin) or tetracycline antibiotics (doxycycline) — separate by at least 2 hours.
- You take penicillamine — separate by at least 2 hours.
- You take levothyroxine — separate by at least 4 hours.
- You take prescribed iron — high-dose zinc and high-dose iron compete; space the doses.
- You are pregnant or breastfeeding — RNI-level intake from food and standard supplements is fine; do not exceed the RNI without specific advice.
- You are considering zinc lozenges or AREDS-dose zinc for an eye condition — these uses warrant a conversation with your pharmacist or specialist first.
Common side effects: Nausea, stomach upset, and a metallic taste are the most common short-term side effects, especially on an empty stomach or with lozenges.
Pregnancy and breastfeeding
The NHS does not raise the zinc RNI in pregnancy (7 mg/day for women remains the recommendation). Routine supplementation at the RNI level is generally regarded as safe in pregnancy. The NHS does not routinely recommend zinc supplementation in pregnancy. Do not exceed the RNI without specific advice from your midwife, GP, or pharmacist, and avoid AREDS-dose or megadose zinc products in pregnancy.
The SACN reference intake adds approximately 6 mg/day above the women's RNI during the first 4 months of lactation (giving roughly 13 mg/day). Easily achievable from a varied diet that includes meat, dairy, eggs, pulses, and wholegrains.
Talk to your GP, midwife, or pharmacist before starting any supplement during pregnancy or breastfeeding.
More clinical detail (for clinicians and informed readers)
Contraindications
- Wilson's disease — zinc is used therapeutically in this condition under specialist supervision; do not self-supplement.
- Known copper deficiency — additional zinc will worsen it.
Drug interactions
- Quinolone antibiotics (ciprofloxacin, levofloxacin, moxifloxacin) — zinc reduces absorption; separate by at least 2 hours (BNF Appendix 1).
- Tetracycline antibiotics (doxycycline, lymecycline) — zinc reduces absorption; separate by at least 2 hours (BNF Appendix 1).
- Penicillamine — zinc forms a complex that reduces both drug and mineral absorption; separate by at least 2 hours (BNF Appendix 1).
- Levothyroxine — zinc may reduce thyroxine absorption; separate by at least 4 hours.
- High-dose iron supplements — zinc and iron compete for the same intestinal transporter at higher supplemental doses; separate by 2 hours where possible.
- High-dose calcium supplements — may reduce zinc absorption; nutritional-dose interference is small.
- Thiazide diuretics — long-term thiazide use may increase urinary zinc loss; clinical significance is modest but worth flagging to your prescriber.
This is not an exhaustive list. Always tell your prescriber and pharmacist about every supplement you take.
Common side effects
- Nausea and stomach upset — most common when zinc is taken on an empty stomach.
- Metallic taste with lozenges.
- Mouth or throat irritation with lozenges (high-zinc-acetate lozenges in particular).
Rare side effects
- Copper deficiency, sideroblastic anaemia, and neutropenia from chronic intake above ~40 mg/day.
- Neurological symptoms (myelopathy, peripheral neuropathy) from sustained high-dose excess (typically months to years above 100 mg/day).
- Loss of smell historically reported with intranasal zinc gluconate products (those products were withdrawn) — not a risk with oral or lozenge use.
How to take it
- UK Reference Nutrient Intake
- 9.5 mg/day (men) · 7 mg/day (women)
- Typical supplemental range
- 10-25 mg/day in supplemental form for general use
- UK upper limit (supplemental)
- 25 mg/dayThe NHS advises not to take more than 25 mg/day of zinc from supplements unless advised by a doctor. The EU SCF (2003) set the Tolerable Upper Intake Level at 25 mg/day for adults from total intake including food. AREDS-formula doses (25 mg in AREDS2, 80 mg in original AREDS) are clinically supervised exceptions and are paired with copper to prevent secondary deficiency.
- Timing
- With food to reduce nausea — empty-stomach zinc commonly causes stomach upset.
How to spot quality
Look for
- Form named on the label: zinc gluconate, citrate, sulfate, picolinate, or bisglycinate (also called glycinate) for general supplementation; zinc acetate for cold-shortening lozenges.
- Elemental zinc amount stated alongside the compound mass (e.g. "zinc bisglycinate 75 mg, providing 15 mg elemental zinc").
- GB NHC threshold compliance: at least 1.5 mg elemental zinc per recommended daily portion (15% of 10 mg NRV) to make any authorised "zinc contributes to..." claim.
- GMP-certified manufacture; ideally third-party heavy-metals testing (especially for marine-source zinc).
Red flags
- Megadose marketing (50 mg, 75 mg "high-strength immune zinc") aimed at the general consumer, without copper pairing or medical context.
- "Boosts immunity" or "immune megadose" wording — the authorised UK claim is "contributes to normal function".
- Lozenges that are zinc gluconate or picolinate without explicit cold-duration framing — gluconate lozenges have a weaker evidence base than zinc acetate, although Hemilä 2017 found both can work; picolinate lozenges are not the form studied for cold-shortening.
- Zinc combined with high-dose iron and high-dose calcium in a single capsule — mutual absorption interference reduces effective dose of all three.
- Form simply listed as "zinc" with no compound named, or an oxide-only product without mention of elemental amount.
Where Camden lands · meets the bar
Camden's catalogue currently delivers zinc as a co-ingredient in NB-537 (Shilajit Adaptogen Complex) — 5 mg elemental zinc per 2-capsule serving (50% NRV), as zinc citrate. Form is named, the elemental amount is declared, and the dose clears the 1.5 mg / 15% NRV threshold for the GB-authorised zinc claims. There is no standalone Camden zinc SKU in the catalogue at the time of writing; adults wanting routine zinc adequacy from a dedicated supplement will want a 10–15 mg standalone product. We are evaluating a standalone NB- zinc product.
Commonly combined with
Other ingredients that share a biological pathway, cofactor relationship, or evidence-backed protocol with this one. Mechanisms below cite primary physiology — not folk pairing. Doses are literature ranges, not recommendations. Talk to your pharmacist or GP before changing your stack, especially if you take prescription medication.
Biotin
Limited evidenceBeauty-cluster pairing — biotin keratinocyte FA + zinc keratinocyte zinc-finger transcription factors.
Biotin enzyme cofactor + zinc keratinocyte zinc-finger transcription. Different mechanisms; complementary on hair / skin / nails axis.
Evidence: Beauty-cluster co-formulation. [2,2]
Doses studied: 50-200 µg biotin + 10-15 mg zinc daily.
Echinacea (Echinacea purpurea / E. angustifolia / E. pallida)
Limited evidenceAcute-cold cluster pairing — echinacea immune-modulation + zinc anti-rhinoviral activity for cold-symptom duration.
Zinc lozenges (zinc gluconate or zinc acetate at 75-100 mg/day in divided doses across the day) have Cochrane review support (Hemilä 2017) for reducing common-cold duration when started within 24 hours of symptom onset — mechanism is direct antiviral effect against rhinovirus replication in the upper respiratory tract via zinc binding to the rhinovirus 3C-protease. Zinc also carries the UK Article 13.1 authorised claim "Zinc contributes to the normal function of the immune system".
Echinacea acts on the immune-modulation axis (alkamides, polysaccharides). The combination is mechanism-additive: zinc on the antiviral axis, echinacea on the immune-modulation axis. Combination trials are small but the each-component trial bases support short-course acute-cold use. The combination appears in many UK cold-symptom lozenges and effervescent tablets (alongside vitamin C).
Evidence: Zinc lozenges have Cochrane support for cold-symptom duration (Hemilä). Echinacea Cochrane evidence is mixed. UK Article 13.1 authorised immune claims for both zinc and vitamin C. [2]
Doses studied: Echinacea purpurea extract 200-500 mg + zinc gluconate 10-25 mg per dose (high-dose zinc gluconate / acetate 75-100 mg/day in divided lozenge doses for the cold-duration effect), 7-10 day acute course.
Elderberry (Sambucus nigra, Black Elder)
Limited evidenceAcute-cold-symptom cluster pairing — elderberry direct antiviral activity plus zinc anti-rhinoviral activity for cold-symptom duration.
Zinc lozenges (zinc gluconate or zinc acetate at 75-100 mg/day in divided doses across the day, taken within 24 hours of cold-symptom onset) have Cochrane review support (Hemilä) for reducing common-cold duration via direct antiviral effect against rhinovirus 3C-protease. Zinc carries the UK Article 13.1 authorised immune claim. Elderberry provides direct antiviral activity against influenza A, influenza B, and several rhinoviruses via anthocyanin binding to viral surface glycoproteins.
The combination is mechanism-additive on the antiviral axis, with the zinc contributing the UK authorised immune claim. The combination appears widely in UK acute-cold lozenges, syrups, and effervescent tablets, and is part of NB-1284's active mix.
Evidence: Zinc Cochrane evidence supportive for cold duration. Elderberry systematic review evidence supportive. Combined trials limited. [2]
Doses studied: Elderberry extract 300-1000 mg + zinc gluconate / zinc citrate 10-25 mg per dose (high-dose zinc lozenge regimen 75-100 mg/day in divided doses for the cold-duration effect), 5-10 day acute course.
Iodine (I)
Limited evidenceIodine, selenium, and zinc are the three trace-mineral inputs to thyroid hormone synthesis and signalling. Zinc plays a smaller role than selenium but features in some thyroid-cluster formulations.
Zinc is required for the function of thyrotropin-releasing hormone (TRH) signalling and for thyroid hormone receptor binding to DNA at the nuclear thyroid hormone response elements. Zinc deficiency has been associated in some populations with reduced T3 levels and impaired thyroid hormone action, though the effect is more modest than selenium deficiency.
The iodine-selenium-zinc thyroid trio appears in some pregnancy multivitamins and in dedicated thyroid-support products. The mechanism is supportive — adequate zinc status enables normal thyroid hormone signalling — rather than synergistic. UK Article 13.1 claim wording for zinc does NOT include thyroid (zinc claims cover cognitive function, immune system, protein and DNA synthesis, testosterone maintenance, fertility, acid-base / carbohydrate metabolism).
Evidence: Mechanism (zinc role in thyroid hormone receptor and TRH signalling) is established. Direct trial evidence for combined iodine-zinc supplementation is limited. UK Article 13.1 claims for zinc do not include thyroid wording. [2]
Doses studied: 150 µg/day iodine with 10-15 mg/day zinc citrate or zinc picolinate. Most UK general multivitamins include both at NRV-equivalent doses.
Niacinamide (Topical, Vitamin B3 amide form)
Limited evidenceAcne-cluster pairing — The Ordinary 10% Niacinamide + 1% Zinc is the foundational UK product. Zinc adds sebum modulation and modest antibacterial activity to niacinamide's ceramide + anti-inflammatory axes.
Zinc PCA (the cosmetic form in The Ordinary's product) modulates 5-α-reductase activity in sebocytes (reducing dihydrotestosterone-driven sebum) and has modest antibacterial activity against Cutibacterium acnes (the primary acne-associated bacterium). Niacinamide adds separate sebum modulation (mechanism unclear), barrier rebuild via ceramide synthesis, and anti-inflammatory PGE2 reduction.
The combination is mechanism-additive on the acne axis without overlapping. UK NICE NG198 first-line for moderate-to-severe acne is prescription topical retinoid + benzoyl peroxide; the niacinamide-zinc combination is cosmetic-tier adjunct for mild acne.
Evidence: Mechanism complementary across sebum / antibacterial axes. Direct combination trial evidence small; The Ordinary product RCTs supportive at 10% niacinamide + 1% zinc. [9,2]
Doses studied: 10% niacinamide + 1% zinc PCA topical, 1-2× daily.
Polypeptides (Cosmetic peptides — signal / carrier / neurotransmitter-inhibiting)
Limited evidenceTrace-metal cofactor cluster — copper peptide (GHK-Cu) carries copper to lysyl oxidase; zinc supports separate enzymatic targets (carbonic anhydrase, zinc-finger transcription factors). Mechanism-adjacent.
Copper and zinc are both trace-metal cofactors at distinct enzymatic targets. GHK-Cu specifically delivers copper to wound-healing-pathway enzymes; oral or topical zinc supports separate metalloenzyme activity. Different metals, different mechanisms.
Evidence: Mechanism-adjacent; not directly synergistic. [2]
Doses studied: GHK-Cu topical 1-3% + oral zinc 10-15 mg/day or topical zinc PCA in acne products.
Saw Palmetto
Limited evidenceMen's-health cluster — both feature in BPH / prostate-supportive supplementation framings.
Saw palmetto fatty-acid lipidosterolic extract modulates 5-α-reductase + androgen-receptor signalling; zinc modulates testosterone metabolism + 5-α-reductase. Mechanism complementary on androgen-axis.
Evidence: UK Article 13.1 zinc testosterone-maintenance claim authorised. [2]
Doses studied: 320 mg saw palmetto extract + 10-15 mg zinc daily.
Vitamin C topical (L-ascorbic acid + ester derivatives)
Limited evidenceAntioxidant cluster — zinc supports superoxide dismutase (SOD) activity; vitamin C scavenges ROS directly. Mechanism-complementary.
Zinc is the structural metal at the active site of cytosolic Cu/Zn-SOD, the principal antioxidant enzyme converting superoxide to hydrogen peroxide. Vitamin C scavenges superoxide and other ROS directly. Different mechanisms; complementary on the antioxidant axis. UK Article 13.1 cell-protection claims for both.
Evidence: Mechanism complementary; UK Article 13.1 cell-protection claims for both. [2]
Doses studied: Topical vitamin C AM + oral zinc 10-15 mg/day.
Selenium
Moderate evidenceAntioxidant + immune cluster — selenium glutathione peroxidase + zinc SOD complementary.
Different metalloenzyme cofactor roles; UK Article 13.1 immune claims for both.
Evidence: UK Article 13.1 claims authorised. [2,2]
Doses studied: 100-200 µg selenium + 10-15 mg zinc daily.
Vitamin C
Moderate evidenceImmune-cluster classic pairing — UK Article 13.1 immune claims for both. Cochrane support for cold-symptom duration with high-dose zinc lozenges.
Vitamin C is required for normal immune-cell function (neutrophil chemotaxis, lymphocyte proliferation, oxidative-burst capacity) and carries the UK Article 13.1 authorised claim "Vitamin C contributes to the normal function of the immune system." Zinc provides separate immune-cell function support and direct anti-rhinoviral activity (zinc binding to rhinovirus 3C-protease). Both nutrients hold UK Article 13.1 immune claims; the combination is the textbook UK winter-immune formulation.
Evidence: Cochrane reviews of zinc lozenges show modest reduction in cold duration at higher zinc doses. UK Article 13.1 claims authorised for both vitamin C and zinc on immune function. [2,2]
Doses studied: 10–25 mg zinc with 80–1000 mg vitamin C daily
Vitamin D3
Strong evidenceImmune-cluster trio with vitamin C — three different UK Article 13.1 immune-claim mechanisms stacked.
Vitamin D3 induces antimicrobial peptide expression (cathelicidin LL-37, defensins) in monocytes and respiratory epithelium and modulates Th1/Th17 responses. Zinc supports immune-cell function separately and has direct anti-rhinoviral activity (zinc binding to rhinovirus 3C-protease). Vitamin C supports neutrophil chemotaxis + lymphocyte proliferation. Three separate mechanisms, three separate UK Article 13.1 immune claims — classical winter-immune formulation.
Evidence: All three nutrients carry UK Article 13.1 authorised claim "contributes to the normal function of the immune system." Vitamin D + winter respiratory infection: Martineau 2017 IPD meta-analysis (BMJ) supportive in deficient subgroups. [2,2]
Doses studied: 10–25 mg zinc + 10–25 µg vitamin D3 + 80–1000 mg vitamin C daily