Zinc
Only when you eat little of it or a level is low, and always counted against the upper limit with everything else you take.
At a glance
| Our verdict | Only when intake is low (vegan, little meat) or a level is measured low. Counted against the upper limit with everything else. |
| Best use | Low intake or a low level |
| How sure the evidence is | Very low to moderate (children's trials only) |
| Cost a month | About $5 to $8 |
Written for adults in Canada. It explains the evidence; it is not advice for you personally. Last reviewed 20 October 2026.
Supplement Check
Is it right for you?
Zinc hides in multivitamins, eye formulas and many other products, and too much of it causes copper deficiency. We add up the zinc in everything you take before suggesting more. Our Supplement Check looks at:
- Already taking the AREDS2 eye formula
- More than 40 mg a day for a long time
- Men with an enlarged prostate or urinary problems who need the eye formula
- Kidney disease with kidney function (eGFR) under 30
- Pregnancy and breastfeeding
- Every medicine you take
- The total across everything you already take, against the safe upper limits
Coming soon. The Supplement Check and the Online Health Assessment open once our safety testing is complete.
$59 when it opens, paid once. Adults 18 and over, anywhere in Canada. While the service is new, Dr. French reads every report himself, and your report arrives within 3 working days. More about the Supplement Check
What it is
Zinc is an essential trace mineral. It is already in multivitamins (an age-50+ multivitamin has 11 mg; a standard multivitamin 7.5 to 15 mg) and in eye formulas (the AREDS2 eye formula caplets give 80 mg a day, the low-zinc softgel 25 mg).
We have not named a zinc product. Zinc on its own is cheap and widely licensed in Canada.
How it acts
Zinc is a helper for many enzymes, including some that handle dopamine, and it binds the dopamine transporter in the brain; that is the proposed link with attention and hyperactivity. These are mechanisms, not proof.
What it is used for, and what the evidence says
Our sources for zinc are thin. The trials we found are almost all in children with attention deficit hyperactivity disorder (ADHD), plus the eye-formula trials; adult trials of zinc on its own were not part of our review.
| Use | What the trials found | How sure we are |
|---|---|---|
| ADHD in children, 6 trials | 489 children: the total ADHD score improved (standardised difference −0.62), but the range of the estimate reached almost zero, and attention did not improve. [1] | Very low to Moderate |
| ADHD in children, the largest trial | 400 children in Turkey, zinc sulfate 150 mg (about 34 mg of zinc) for 12 weeks: less hyperactivity and impulsivity and better social behaviour, but not better attention; 28.7% responded against 20%. [2] | Low |
| ADHD in children, with amphetamine | 52 children in the US: equivocal; with 30 mg a day of zinc the best amphetamine dose was 37% lower. [3] | Low |
| ADHD in adults | None found. | No evidence (no trial) |
| Macular degeneration (zinc in the eye formula) | Over 10 years, 25 mg of zinc protected the eye as well as 80 mg (hazard ratio 1.04). [4] | Moderate |
| High doses | 80 mg a day in the eye trial: hospital admissions for urinary and genital problems 11.1% against 7.6%, mostly in men. [5] | Not graded |
How sure we are: High means further research is very unlikely to change the answer; Moderate, it might; Low, it may well change; Very low, we are very unsure. These follow the GRADE method that guideline panels use.
Benefits
- Corrects a low intake, for example on a vegan diet or with little meat.
- In children with ADHD, a possible small effect on hyperactivity, not attention (very low to moderate certainty), likely only where intake or the level is low.
- Cheap.
Risks and side effects
- Nausea.
- Copper deficiency with long-term high doses: anaemia, low white cells and nerve damage. This is why the AREDS2 eye formula carries copper.
- Urinary and genital problems at 80 mg a day, mostly in men. [5]
- The upper limit is 40 mg a day from all sources. [6] A multivitamin plus the full-zinc eye formula comes to 91 mg.
Interactions with medicines
Our sources list no effect of zinc on how the liver clears medicines. Its interactions come from binding in the gut.
| Medicine | What can happen | What to do |
|---|---|---|
| Quinolone and tetracycline antibiotics | Zinc binds them and less is absorbed | Space by 2 to 4 hours |
| Levothyroxine, bone medicines (bisphosphonates) | Less is absorbed | Space by 4 hours |
| Penicillamine | Less penicillamine is absorbed | Noted in your review |
| Iron | Competes with zinc for absorption | Space the doses |
Who should not take it
- Already taking the AREDS2 eye formula: no separate zinc.
- More than 40 mg a day for a long time: only with a doctor's review. The one exception is diagnosed macular degeneration on the high-zinc eye formula: up to 95 mg in total, with at least 2 mg of copper.
- Men with an enlarged prostate or urinary problems who need the eye formula: the low-zinc version.
- Kidney disease with kidney function (eGFR) under 30: zinc and copper build up; for a physician.
- Pregnancy and breastfeeding: not covered in our review.
- Under 18: outside the Supplement Check.
Dose and timing
- Only when intake is low (vegan, little meat) or a level is measured low.
- 15 to 25 mg of zinc a day with food, for 12 weeks, then review.
- Every product is added up first: zinc from your multivitamin, eye formula and anything else counts against the 40 mg limit before we suggest more.
- How to tell it is working: our review found no reliable sign or test target to follow.
- Store at room temperature.
What we know about Canadians
About a quarter to a third of Canadian adults eat less zinc than the average requirement: 21–44% of men and 30–35% of women, depending on age, in the 2015 national nutrition survey. [7] Food insecurity raises the shortfall (35% against 23% among adults 19 to 64). [8] A Canadian analysis found that intakes reach the upper limit for zinc only when supplements are added. [9] Canada has no national blood zinc survey.
Most at risk: men over 70, food-insecure households, vegetarians and vegans, people with bowel disease, heavy alcohol use, or long-term water pills.
How sure are we: moderate (intake); very low (zinc status). National survey of recalled food from 2015; no blood data on zinc in Canada.
An honest comparison: ADHD symptoms
The only outcome in our review with numbers for zinc. The zinc trials were in children, mostly rated by parents, and are not directly comparable with the medicine trials. Zinc is not a substitute for ADHD treatment.
| Option | Effect | How sure we are | Cost a month (CAD) |
|---|---|---|---|
| Zinc (children) | Total score better (standardised difference −0.62), with a range reaching almost zero; attention not better [1] | Very low to Moderate | $5 to $8 |
| Aerobic exercise (children) | Attention better (standardised difference 0.84); hyperactivity and impulsivity 0.56 [10] | Low | $0 to $21 |
| Stimulant medicine | Methylphenidate −0.78 in children; amphetamines −0.79 in adults (clinician-rated) [11] | Moderate to High | $50 to $150 |
Our verdict
Zinc 15 to 25 mg a day when your diet supplies little (vegan, or little meat) or a level is measured low, counted with the zinc in everything else you take.
Not on top of the AREDS2 eye formula, and not above 40 mg a day long term without a doctor's review.
A quarter to a third of Canadians eat less zinc than they need, but there is no national blood survey, and our review found no adult trial of zinc on its own. The children's ADHD trials suggest a small effect at best. The harm that matters is too much: zinc is in many products, and a long-term excess causes copper deficiency. So we give it only for a reason, and Dr. French's stacking rule adds up every source against the upper limit first. Our evidence for zinc is thin, and we say so.
Supplement Check
Before you buy it, get it checked
Zinc hides in multivitamins, eye formulas and many other products, and too much of it causes copper deficiency. We add up the zinc in everything you take before suggesting more. Our Supplement Check looks at:
- Already taking the AREDS2 eye formula
- More than 40 mg a day for a long time
- Men with an enlarged prostate or urinary problems who need the eye formula
- Kidney disease with kidney function (eGFR) under 30
- Pregnancy and breastfeeding
- Every medicine you take
- The total across everything you already take, against the safe upper limits
Coming soon. The Supplement Check and the Online Health Assessment open once our safety testing is complete.
$59 when it opens, paid once. Adults 18 and over, anywhere in Canada. While the service is new, Dr. French reads every report himself, and your report arrives within 3 working days. More about the Supplement Check
Disclosure of financial interest
White Pine Medical earns money from products bought through our Fullscript dispensary. Dr. French's Code of Ethics requires him to tell you this. You do not have to buy anything from us: every product is named by its ingredient and dose so you can buy it at any pharmacy, and the advice is the same wherever you buy it, or if you buy nothing.
References
- Talebi S, Miraghajani M, Ghavami A, Mohammadi H. The effect of zinc supplementation in children with attention deficit hyperactivity disorder: a systematic review and dose-response meta-analysis of randomized clinical trials. Crit Rev Food Sci Nutr. 2022;62(32):9093-102.
- Bilici M, Yildirim F, Kandil S, et al. Double-blind, placebo-controlled study of zinc sulfate in the treatment of attention deficit hyperactivity disorder. Prog Neuropsychopharmacol Biol Psychiatry. 2004;28(1):181-90.
- Arnold LE, Disilvestro RA, Bozzolo D, et al. Zinc for attention-deficit/hyperactivity disorder: placebo-controlled double-blind pilot trial alone and combined with amphetamine. J Child Adolesc Psychopharmacol. 2011;21(1):1-19.
- Chew EY, Clemons TE, Agrón E, Domalpally A, Keenan TDL, Vitale S, et al. Long-term outcomes of adding lutein/zeaxanthin and ω-3 fatty acids to the AREDS supplements on age-related macular degeneration progression: AREDS2 report 28. JAMA Ophthalmol. 2022;140(7):692-8.
- Johnson AR, Munoz A, Gottlieb JL, Jarrard DF. High dose zinc increases hospital admissions due to genitourinary complications. J Urol. 2007;177(2):639-43.
- Health Canada. Dietary reference intakes tables: reference values for elements [Internet]. Ottawa: Health Canada; [read 20 Oct 2026]. Available from: https://www.canada.ca/en/health-canada/services/food-nutrition/healthy-eating/dietary-reference-intakes/tables/reference-values-elements.html
- Ahmed M, Praneet Ng A, L'Abbe MR. Nutrient intakes of Canadian adults: results from the Canadian Community Health Survey (CCHS)-2015 Public Use Microdata File. Am J Clin Nutr. 2021;114(3):1131-40.
- Hutchinson JM, Tarasuk V. Prevalence of micronutrient inadequacy differs by severity of food insecurity among adults living in Canada in 2015. Appl Physiol Nutr Metab. 2024;49(8):1025-34.
- Tarasuk V, Brassard D. The effect of consuming voluntarily fortified food and beverages on usual nutrient intakes in the Canadian population. Food Nutr Res. 2021;65.
- Cerrillo-Urbina AJ, García-Hermoso A, Sánchez-López M, Pardo-Guijarro MJ, Santos Gómez JL, Martínez-Vizcaíno V. The effects of physical exercise in children with attention deficit hyperactivity disorder: a systematic review and meta-analysis of randomized control trials. Child Care Health Dev. 2015;41(6):779-88.
- Cortese S, Adamo N, Del Giovane C, Mohr-Jensen C, Hayes AJ, Carucci S, et al. Comparative efficacy and tolerability of medications for attention-deficit hyperactivity disorder in children, adolescents, and adults: a systematic review and network meta-analysis. Lancet Psychiatry. 2018;5(9):727-38.
Costs marked as estimates are typical Canadian retail or pharmacy prices, before any drug plan. Certainty grades are ours unless the review gave its own.