What Is Zinc Picolinate? The 1987 Study, Elemental Zinc and Forms

Zinc picolinate is zinc bound to picolinic acid, a compound the body itself makes from the amino acid tryptophan; it is about 21% zinc by weight, and its reputation for absorption rests on one 1987 study of 15 volunteers that measured hair, urine and red-cell zinc rather than absorption itself, and no tracer study has tested it since.^{1, 2, 3} The same wording applies to every form: zinc contributes to the normal function of the immune system and to the maintenance of normal skin, hair and nails.⁴ UK adults need about 9.5 mg a day for men and 7 mg for women, and the NHS says: "Do not take more than 25mg of zinc supplements a day unless advised to by a doctor."⁵ Part of the Wellgard zinc guide; see also which type of zinc is best.

Sources checked on 30 October 2026.

What is zinc picolinate, and what is picolinic acid?

Picolinic acid is a small organic acid the body produces from tryptophan along the kynurenine pathway; a 2009 review calls it "an endogenous metabolite of L-tryptophan" whose main physiological function "is yet to be established".¹ Two picolinate molecules bind one zinc atom, which is why some labels say "chelated": the word describes the bond. The authorised zinc wordings on the GB register attach to the zinc, not the carrier; no form has a claim of its own, and no absorption comparison is an authorised claim.⁴

How much elemental zinc is in zinc picolinate?

About 21%. Picolinic acid has a formula weight of about 123 and zinc about 65, so zinc picolinate, with two picolinates to each zinc, weighs about 310: 100 mg of the compound carries about 21 mg of zinc, and 22 mg of zinc needs roughly 104 mg of zinc picolinate.

A UK label does the arithmetic for you: it gives elemental zinc with a percentage of the 10 mg nutrient reference value, so "zinc 22 mg (220% NRV)" means 22 mg of zinc, not of compound.⁶ At 22 mg a capsule you are inside the NHS 25 mg line only if nothing else you take carries zinc; at 50 mg you are at twice it.⁵ How much zinc a day sets out the UK figures.

What did the 1987 study find?

It was a double-blind, four-period crossover in 15 healthy volunteers, each rotating through four-week periods of zinc picolinate, citrate and gluconate, each supplying 50 mg of elemental zinc a day, and placebo. After four weeks, hair, urine and red-cell zinc had risen significantly during the picolinate period (p < 0.005, p < 0.001 and p < 0.001); none of these changed significantly during the gluconate, citrate or placebo periods; and serum zinc showed only "a small, insignificant rise" during picolinate, citrate and placebo alike. The authors concluded that the results "suggest that zinc absorption in humans can be improved by complexing zinc with picolinic acid".² That is 15 people, 50 mg a day, and absorption inferred from where zinc turned up afterwards rather than measured as it crossed the gut.

What has been studied since 1987?

Not picolinate's absorption. The most rigorous comparison of zinc forms, a supplier-funded 2014 study, used a double-isotope tracer in 15 healthy adults given 10 mg of zinc without food in a randomised crossover: median absorption was 61.3% from zinc citrate and 60.9% from zinc gluconate and 49.9% from zinc oxide, significantly lower (P < 0.01), a result the authors tie to a supplement "given without food".³ Later trials used picolinate without comparing it with another form: in one, 73 patients with a taste disorder attributed to zinc deficiency showed no significant difference in subjective symptoms after three months, but a significantly better filter-paper taste test and a higher serum zinc.⁷

How does zinc picolinate compare with citrate, gluconate and oxide?

On the facts, without a ranking: picolinate has one 1987 study using indirect markers; citrate and gluconate have one 2014 tracer study in which they were absorbed equally; oxide, in the same study, was absorbed less when taken without food and was not tested with a meal.^{2, 3}

Does zinc picolinate have different side effects?

The 1987 abstract reports no side effects, so the answer comes from what is known about zinc at a given dose.² In a 1987 Australian trial, 47 healthy volunteers took 50 mg of zinc three times a day for six weeks: headaches, abdominal cramps, nausea, loss of appetite and vomiting were reported by 84% of the women and 18% of the men.⁸ A picolinate capsule at 22 or 25 mg of zinc is a higher single dose than most multi-nutrient products carry, a reason to take it with a meal, not to expect a different kind of side effect. Can you take too much zinc covers higher doses.

Who should not take zinc picolinate, and what should you avoid taking it with?

The same people, and the same things, as for any zinc. The NHS line comes first: "Do not take more than 25mg of zinc supplements a day unless advised to by a doctor", because "Taking high doses of zinc reduces the amount of copper the body can absorb. This can lead to anaemia and weakening of the bones."⁵ No NHS or regulatory document sets a zinc to copper ratio, so "what ratio for 50 mg of zinc picolinate" has no official answer; copper has its own NHS line of 10 mg a day from food, water and supplements, and 50 mg of zinc a day is a dose for a doctor to advise.⁵ Zinc and copper sets out the evidence.

Count the total: a multivitamin, a vitamin C and zinc product and a picolinate capsule can together pass 25 mg (vitamin C and zinc together). With antibiotics: ciprofloxacin tablets' prescribing information says to take the antibiotic "either 1-2 hours before or at least 4 hours after" mineral supplements (zinc salts included, says the UK Expert Group on Vitamins and Minerals); the NHS lists zinc supplements among things that "may not mix well" with doxycycline, so tell your pharmacist (what should you not take with zinc).^{9, 11, 12} Iron reduces zinc absorption "if given together in a supplement", though not in a meal, so take an iron tablet at a different time of day.¹⁰ Anyone on penicillamine or another long-term medicine asks a pharmacist first. In pregnancy and breastfeeding the 25 mg line still applies; ask your GP or midwife, and for a child a pharmacist or GP. Symptoms need a GP: see signs of zinc deficiency; the vitamins and minerals guide covers the other minerals.

What we don't know

Whether picolinate's absorption differs from citrate or gluconate when measured directly: no tracer study has included it, so the 1987 markers and the 2014 isotope figures cannot be laid side by side.^{2, 3} Whether the form changes anything a person would notice: the comparisons measure absorption and blood markers, not outcomes.^{2, 3, 7} Whether picolinate differs in side effects at label doses: the 1987 abstract reports none, and the form comparisons did not report nausea as an outcome.^{2, 3, 8}

Frequently asked questions

Is it safe to take zinc picolinate every day?

Within the NHS line, yes: 25 mg or less of zinc a day from every supplement you take, unless a doctor has advised more.⁵ The 1987 study ran four weeks at 50 mg; the NHS figure is the one for daily use over years.²

What is the difference between zinc picolinate and zinc?

Picolinate is one of the carriers that deliver zinc in a capsule. "Zinc 22 mg" on a UK label is the elemental zinc, whatever the carrier, and the figure to compare against 25 mg.⁶

Is zinc picolinate better than zinc citrate or zinc gluconate?

Not shown either way. The 1987 study's indirect markers rose only with picolinate; the 2014 tracer study found citrate and gluconate absorbed equally and did not include picolinate.^{2, 3}

Is zinc picolinate good for men?

The wording that applies to men applies to zinc in any form: zinc contributes to the maintenance of normal testosterone levels in the blood and to normal fertility and reproduction.⁴ The picolinate studies measured zinc markers and taste, nothing specific to men; see what does zinc do for men.^{2, 7}

Can I take zinc picolinate before bed?

You can, with food if evening capsules make you queasy. Zinc has no authorised sleep wording; see which vitamin deficiency affects sleep.

Sources

1. Grant RS, et al. The physiological action of picolinic acid in the human brain. International Journal of Tryptophan Research, 2009. Narrative review; funding not stated on PubMed. PubMed 22084583.
2. Barrie SA, et al. Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans. Agents and Actions, 1987. Double-blind crossover, 15 volunteers, 50 mg a day for four weeks per form; public or charity funding listed on PubMed. PubMed 3630857.
3. Wegmüller R, et al. Zinc absorption from zinc citrate, gluconate and oxide. Journal of Nutrition, 2014. Randomised crossover tracer study, 15 adults, single 10 mg doses without food; supplier-funded (a zinc citrate manufacturer). PubMed 24259556.
4. Great Britain nutrition and health claims (NHC) register, zinc entries. Updated 19 May 2026. gov.uk.
5. NHS. Vitamins and minerals: others (zinc and copper). Page last reviewed 3 August 2020 (review overdue). nhs.uk.
6. Retained Regulation (EU) No 1169/2011, Annex XIII, nutrient reference values. Regulation. legislation.gov.uk.
7. Sakai F, et al. Double-blind, placebo-controlled trial of zinc picolinate for taste disorders. Acta Oto-Laryngologica, 2002. Randomised placebo-controlled trial, 73 patients, 3 months; funding not stated on PubMed. PubMed 12132610.
8. Samman S, Roberts DC. Zinc supplements, plasma zinc and copper, and reported symptoms in healthy volunteers. Medical Journal of Australia, 1987. Double-blind crossover, 47 volunteers, 150 mg a day for six weeks; public or charity funding listed on PubMed. PubMed 3547053.
9. Ciprofloxacin 500 mg film-coated tablets. Summary of Product Characteristics (licensed product information), section 4.5, revised 29 May 2026. medicines.org.uk.
10. Lönnerdal B. Dietary factors influencing zinc absorption. Journal of Nutrition, 2000. Narrative review; funding not stated on PubMed. PubMed 10801947.
11. Expert Group on Vitamins and Minerals. Safe Upper Levels for Vitamins and Minerals, 2003. Expert committee report. UK Government Web Archive.
12. NHS. Doxycycline. Page last reviewed 5 September 2025. nhs.uk.

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This article is general information, not medical advice. Do not take more than 25 mg of zinc a day from supplements unless a doctor has advised it, and ask a pharmacist before combining zinc with any medicine.