Zinc forms compared: what counts on the label
Futures Nutrition Editorial Team · 12 August 2026
Zinc forms compared: what counts on the label
The good news first: with zinc, comparing two packages is easier than the carousel of forms suggests. The nutrition table of a food supplement states the amount of elemental zinc — not the amount of the compound it comes from. "Zinc 10 mg" therefore means the same thing for gluconate as it does for bisglycinate or oxide.
Things go wrong wherever the compound is weighed instead: in the product name, in the ingredients list, in advertising copy. "Zinc gluconate 50 mg" sounds like five times as much as "zinc 10 mg" — in fact it contains around 7 mg of zinc. The share of the element in the compound ranges from about 14 per cent (gluconate) to roughly 80 per cent (oxide). Anyone who has mastered this one distinction has dealt with the most important part of the question of forms.
What has to be on the label
The German Food Supplements Regulation requires the amounts of the nutrients to be stated in relation to the daily portion recommended on the label (NemV § 4 paragraph 3), together with the percentage of the nutrient reference values. Which nutrients these are, and in which unit, is set out in Annex I of Directive 2002/46/EC — where it simply says "zinc (mg)". What is meant is the element.
The corresponding reference value is 10 mg of zinc per day (Regulation (EU) No 1169/2011, Annex XIII). A tablet containing 25 mg of zinc therefore declares 250 % NRV — regardless of how many milligrams of powder are in it.
Three figures that can appear on the same package and mean three different things:
| Statement | What is meant | Useful for comparison? |
|---|---|---|
| "zinc 25 mg" in the nutrition table | amount of the element per daily portion | yes — that is the figure |
| "zinc gluconate" in the ingredients list | the compound used | no — says nothing about the amount |
| "175 mg zinc gluconate" in advertising copy | weight of the compound | only after conversion |
How much zinc sits in which compound
The zinc share follows from the molar masses: zinc weighs 65.4, the rest of the compound is on the scales too. The larger the attached molecule, the smaller the share of the element.
| Compound | calculated zinc share | needed for 25 mg of zinc |
|---|---|---|
| zinc oxide | around 80 % | 31 mg |
| zinc carbonate | around 52 % | 48 mg |
| zinc sulfate (anhydrous) | around 41 % | 62 mg |
| zinc acetate | around 36 % | 70 mg |
| zinc citrate (trizinc dicitrate) | around 34 % | 73 mg |
| zinc bisglycinate | around 31 % | 82 mg |
| zinc lactate | around 27 % | 93 mg |
| zinc picolinate | around 21 % | 118 mg |
| zinc gluconate | around 14 % | 175 mg |
Two qualifications belong with this. First, the values apply to the anhydrous compound; forms with water of crystallisation — zinc sulfate monohydrate or heptahydrate, for instance — lie below them, the heptahydrate at around 23 per cent. Second, some manufacturers sell so-called chelates with a separately stated zinc content that can be lower than the calculated value. In both cases the figure on the label applies, not the one from the table.
In practice, the share mainly explains the size of the tablet: for 25 mg of zinc from gluconate, 175 mg of raw material has to be accommodated; from oxide, only 31 mg. That is why small combination products and multivitamins often contain oxide, while pure zinc preparations frequently use gluconate or citrate. For comparing the price of two packages, though, the raw-material amount is useless — what counts there is the price per day, not the price per milligram of compound.
The same calculation applies to every other mineral, and the names repeat themselves in the process: with magnesium too, the range runs from around 14 per cent elemental share for the bisglycinate to roughly 60 per cent for the oxide. There as well, it is the element that is declared — our magnesium bisglycinate 150 mg supplies 150 mg of elemental magnesium per tablet, no matter how much compound is needed for it. What difference the form makes there is set out in Magnesium forms compared.
Which compounds are permitted at all
The choice is not free. Only those mineral compounds may be used in food supplements that are listed in Annex II of Directive 2002/46/EC (Article 4 paragraph 1). For zinc there are sixteen of them:
zinc acetate, zinc L-ascorbate, zinc L-aspartate, zinc bisglycinate, zinc chloride, zinc citrate, zinc gluconate, zinc lactate, zinc L-lysinate, zinc malate, zinc mono-L-methionine sulfate, zinc oxide, zinc carbonate, zinc L-pidolate, zinc picolinate and zinc sulfate.
What is remarkable about the list is what is missing. Zinc orotate and zinc histidine are regularly recommended in forums, but they are not on the list and may not be used in food supplements in the EU. Conversely, zinc picolinate — contrary to what is often claimed — is explicitly permitted. The list, however, only says what may be used; about absorption it says nothing.
Absorption: what was actually measured
There is less data on bioavailability than the advertising suggests — and the most robust figures come from isotope studies.
The group around Wegmüller at ETH Zurich gave 15 healthy adults preparations containing 10 mg of zinc each in the fasting state and measured absorption using the double-isotope method (The Journal of Nutrition 2014;144(2):132–136, PubMed 24259556). The result:
| Compound | fraction absorbed (median) |
|---|---|
| zinc citrate | 61.3 % |
| zinc gluconate | 60.9 % |
| zinc oxide | 49.9 % |
Citrate and gluconate did not differ from one another; oxide lay significantly below them, and three of the fifteen participants absorbed practically no zinc from it. That is the real point against oxide: not the mean, but the spread.
For zinc picolinate this kind of measurement does not exist. The form's reputation goes back to a study from 1987 in which 15 volunteers received 50 mg of zinc each as picolinate, citrate or gluconate for four weeks; zinc in hair, urine and red blood cells rose significantly only during the picolinate phase (Agents and Actions 1987;21(1–2):223–228, PubMed 3630857). A single, small study almost forty years old using indirect measures — that is all the claim "best absorbed" rests on so far.
More important than the choice between two readily soluble compounds is the company it keeps anyway: the measurements were made in the fasting state. With a meal, absorption falls, and phytate from wholegrains, pulses and nuts slows it down considerably — so much so that the intake recommendations of the D-A-CH societies and the EFSA are graded by daily phytate intake: between 7 and 16 mg of zinc per day for adults. What that means for the time of day, the meal and the gap to other preparations is set out in Taking zinc: timing, meals and spacing.
Reference values, upper limits and what lies between
All the figures that follow refer to elemental zinc — which is the reason the conversion above matters at all.
| Value | Amount | Source |
|---|---|---|
| nutrient reference value (NRV) | 10 mg/day | Regulation (EU) No 1169/2011 |
| recommended intake for adults | 7–16 mg/day depending on phytate intake | D-A-CH 2019 |
| tolerable upper intake level (UL) | 25 mg/day (adults), 22 mg (15–17 years) | SCF 2003 |
| proposed maximum level for food supplements | 6.5 mg per daily portion | BfR 2021 |
The last line is a proposal, not a limit in force: binding maximum levels for minerals in food supplements have not been laid down by the European Commission to this day, although the Directive provides for them. The German Federal Institute for Risk Assessment additionally recommends that products with more than 3.5 mg of zinc per daily portion carry a note not to take further zinc-containing preparations — on the grounds that the usual diet, according to the second German National Nutrition Survey, already supplies a median of 8.6 to 12.3 mg of zinc per day depending on age and sex.
What our preparation contains
Our Zinc 25 mg + vitamin B3 uses zinc gluconate — the compound with the lowest elemental share and the highest measured absorption in the isotope study:
| Per tablet (recommended daily portion) | Amount | % NRV* |
|---|---|---|
| zinc (from zinc gluconate) | 25 mg | 250 % |
| niacin (as nicotinamide) | 25 mg | 156 % |
* Nutrient reference values according to Regulation (EU) No 1169/2011, Annex XIII.
The 25 mg correspond to the tolerable upper intake level for adults and lie well above the BfR's proposed maximum level for food supplements; the recommended use is one tablet daily after a meal. In terms of raw material that means around 175 mg of zinc gluconate per tablet.
Among the claims authorised for zinc are these: Zinc contributes to the normal function of the immune system. Zinc contributes to normal cognitive function. Zinc contributes to normal fertility and reproduction. For niacin: Niacin contributes to normal energy-yielding metabolism. and Niacin contributes to the normal function of the nervous system. (Regulation (EU) No 432/2012). Food supplements are not a substitute for a balanced and varied diet and a healthy lifestyle. What else is in the range is shown by the Zinc category.
Frequently asked questions
Which zinc form is the best? Between the readily soluble compounds — citrate, gluconate, sulfate, acetate, bisglycinate — there is no documented difference in rank that would carry a purchasing decision. What differs in measurement is above all oxide, downwards, and with a wide spread between individuals. The figure that decides remains the amount of elemental zinc per daily portion.
"Zinc gluconate 50 mg" — how much zinc is that? Around 7 mg. At a zinc share of about 14 per cent, the compound delivers only a seventh of its weight as the element. If the package states nothing but the weight of the compound, the very figure the regulation requires is missing.
Is zinc picolinate permitted in the EU? Yes. Zinc picolinate is listed in Annex II of Directive 2002/46/EC and may be used in food supplements. Not permitted are the forms missing from it — zinc orotate, for example.
Why is zinc oxide so often used in multivitamins? Because at around 80 per cent it has the highest zinc share and therefore takes up the least space in the tablet. The price for that is the poorer and markedly more variable absorption shown by the isotope study — particularly relevant when a preparation is taken on an empty stomach anyway.
Sources: Directive 2002/46/EC, Article 4 and Annexes I and II (consolidated version of 2 April 2015) · German Food Supplements Regulation (NemV) § 4 · Regulation (EU) No 1169/2011, Annex XIII · Regulation (EU) No 432/2012 · Wegmüller, Tay, Zeder, Brnić, Hurrell, "Zinc absorption by young adults from supplemental zinc citrate is comparable with that from zinc gluconate and higher than from zinc oxide", The Journal of Nutrition 2014;144(2):132–136 · Barrie, Wright, Pizzorno, Kutter, Barron, "Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans", Agents and Actions 1987;21(1–2):223–228 · German Federal Institute for Risk Assessment, proposed maximum levels for zinc in foods including food supplements, 2021 (with SCF 2003, D-A-CH 2019, EFSA 2014 and the second German National Nutrition Survey).
