What types of zinc are there, and how do they differ?

Zinc in products is never on its own: it is always bound to another substance, and that partner gives each type its name, such as zinc gluconate, zinc sulfate, zinc citrate, zinc acetate, zinc picolinate, zinc bisglycinate or zinc oxide. The types differ in what the zinc is bound to and in how much of the compound's weight is zinc. A 2024 review lists about 14% for zinc gluconate, 23% for zinc sulfate and 80% for zinc oxide. The Thai Reference Daily Intake (Thai RDI) for zinc is 11 mg a day.

This article explains the types by their chemistry and composition only. For what zinc does in the body and the full list of foods that contain it, see What is zinc, and what does it do for the body?

What does "type of zinc" mean?

Zinc is a metal element. In food and in products, it is found as part of a compound, joined to another molecule.

Zinc is always bound to a partner

The NIH Office of Dietary Supplements (ODS), part of the US National Institutes of Health, says supplements can contain a variety of forms of zinc, including zinc sulfate, zinc acetate and zinc gluconate. Each name tells you the partner: sulfate in zinc sulfate, the acetate of acetic acid in zinc acetate, and the gluconate of gluconic acid in zinc gluconate.

Elemental zinc and the weight of the compound

The amount of the zinc element itself within a compound is called elemental zinc. It is always less than the weight of the whole compound, and the two numbers can be far apart: a 2024 review in Molecules from RWTH Aachen University in Germany lists 220 mg of zinc sulfate as containing 50 mg of elemental zinc.

Which zinc compounds are there?

Zinc compounds can be grouped by the partner. The formulas below come from PubChem, the chemistry database of the US National Library of Medicine.

Zinc with an inorganic partner: oxide, sulfate and chloride

Zinc oxide is zinc joined to oxygen, with no other part. Zinc sulfate and zinc chloride are salts of zinc with sulfate and chloride. Zinc sulfate is often listed as the heptahydrate, which means each unit also carries seven water molecules, and that water counts towards its weight.

Zinc with an organic acid: gluconate, citrate and acetate

Gluconic acid, citric acid and acetic acid are organic acids. Acetic acid is the acid of vinegar, and citric acid is the acid found in citrus fruit. Citric acid has three acid groups, so in zinc citrate three zinc atoms are shared between two citrate molecules, which is why its formula has Zn3.

Zinc with an amino acid: bisglycinate

"Bis" means two. In zinc bisglycinate, one zinc atom is bound to two molecules of glycine, the smallest amino acid. It is sometimes called zinc glycinate.

Zinc picolinate

Picolinic acid is a small organic acid containing nitrogen. In zinc picolinate, one zinc atom is bound to two picolinic acid molecules.

How much of each compound is zinc?

The share of zinc depends on how heavy the partner is. Zinc oxide has only a small oxygen atom as its partner, so most of its weight is zinc. Gluconic acid is a large molecule, and two of them come with each zinc atom, so only a small share of zinc gluconate is zinc.

Values listed in a 2024 review

Source: Schoofs, Schmit and Rink, Molecules 2024, table of zinc salts and their elemental zinc content. The review does not list values for zinc citrate, acetate, picolinate or bisglycinate, so they are not shown here.

Why the same amount of zinc can weigh different amounts

Because the share differs, the same amount of zinc comes in very different weights of compound. In the review's example, 220 mg of zinc sulfate contains 50 mg of elemental zinc.

How much zinc do foods contain?

The ODS says oysters contain more zinc per serving than any other food, and that fruits and vegetables contain very little.

Zinc in selected foods

The table shows values from the ODS table, which is based on US Department of Agriculture data, with each serving compared with the Thai RDI of 11 mg.

Where does the zinc in Thai meals come from?

A 1998 study from Ramathibodi Hospital, Mahidol University, looked at 3-day food records from 231 healthy adults aged 20 to 80 in Bangkok and nearby districts. Meat, fish, eggs and milk together supplied 42% of the zinc in their diets, and rice, the staple food, 9%. Average intake was 6.3 mg a day in men and 5.5 mg in women, and was higher in people aged 20 to 39, which the researchers suggest could be explained by a larger share of zinc from animal foods. The study is more than 25 years old and covered one area, so it shows a pattern rather than today's figures for the whole country.

A later 2014 study from the Faculty of Public Health, Mahidol University, looked at 215 office workers aged 20 to 50 at four workplaces in Bangkok, using one 24-hour recall and a 2-day food record. Median zinc intake was 2.1 mg a day in men and 2.3 mg in women. The authors note an important limit: the Thai food database they used had zinc values for only about half of the foods, so these figures count only part of the zinc people actually ate. Self-reported records also tend to under-report food.

How much zinc do you need a day, and how much is too much?

The Thai RDI for zinc is 11 mg a day, for the general population aged 3 and over. The UK's NHS says people should be able to get all the zinc they need from their daily diet.

Upper limits

The ODS gives the following US Tolerable Upper Intake Levels (ULs), which count zinc from both food and supplements.

The NHS advises not taking more than 25 mg of zinc supplements a day unless a doctor advises it.

What happens with too much zinc?

The ODS says high zinc intakes can cause nausea, dizziness, headaches, stomach upset, vomiting and loss of appetite. Doses of 50 mg or more, taken for weeks, can interfere with copper absorption. The NHS likewise says high doses of zinc reduce the amount of copper the body can absorb. The ODS adds that the zinc in food is rarely as high as 50 mg.

Zinc can come from more than one product

Because the upper limit counts zinc from food and supplements together, the total matters. Zinc can be found in multivitamin and mineral products as well as in products with zinc alone, so amounts from several products add up.

Who should talk to a doctor or pharmacist?

People who take regular medication

The ODS says zinc can interact with some medicines: some can reduce how much of both the medicine and the zinc is absorbed, and some can increase the zinc lost in urine. If you take medication regularly, ask a doctor or pharmacist before adding zinc.

Pregnant and breastfeeding women

If you are pregnant or breastfeeding, talk to a doctor or pharmacist before taking any dietary supplement, including zinc.

Dietary supplements are not intended to prevent, treat or cure any disease.