Zinc

What does zinc do in the body?

Zinc is a trace element: a mineral needed in very small quantities, just a few milligrams a day, but it is essential. It is involved in the structure or activation of several hundred enzymes and proteins, including "zinc finger" transcription factors that play a role in DNA reading. The body does not store mobilizable reserves: intake must be regular.

It is one of the micronutrients with the most authorized health claims at the European level, with wording regulated to the letter. The most relevant for this category are:

• "Zinc contributes to the normal function of the immune system."
• "Zinc contributes to normal protein synthesis."
• "Zinc contributes to the maintenance of normal skin."
• "Zinc contributes to the maintenance of normal hair."
• "Zinc contributes to the maintenance of normal nails."
• "Zinc contributes to the maintenance of normal testosterone levels in the blood."
• "Zinc contributes to the protection of cells from oxidative stress."
• "Zinc contributes to normal acid-base metabolism."
• "Zinc has a role in the process of cell division."

All of these claims require the same condition: that the product be at least a "source of zinc," which is 15% of the nutrient reference value. With the NRV being 10 mg, this means 1.5 mg per serving. Pay close attention to what these phrases say: maintenance, normal function, contribution. Zinc does not enhance anything beyond normal, and "maintenance of normal testosterone levels" does not mean it increases it in someone whose levels are already normal.

Bisglycinate, picolinate, citrate, gluconate or oxide: what difference does the form make?

Zinc is never sold pure: it is bound to another molecule, and this partner determines the amount actually absorbed and digestive tolerance. A third point, often overlooked: the elemental zinc content of the salt, which must appear on the label instead of the salt's weight.

Bisglycinate is a chelate: zinc is bound to two glycine molecules. It partly uses peptide absorption pathways, which makes it less sensitive to phytates in whole grains and legumes, and it is among the best tolerated on an empty stomach, with an elemental content of around 20%. This is the form we highlight. Picolinate, bound to picolinic acid, is also well absorbed, at about 21% elemental zinc; citrate offers a good compromise between content - around 31% - and absorption, with a more neutral taste in powder form.

Gluconate is very common, correctly absorbed, but not very concentrated: approximately 14% elemental zinc, which requires larger capsules. Oxide, finally, is the exact opposite: about 80% elemental zinc, a very low price, but poor solubility in the digestive tract, and therefore lower absorption. It is mainly found in entry-level multivitamins, where it inflates the displayed NRV percentage at little cost.

Which foods provide the most zinc?

The ANSES Ciqual table clearly places oysters at the top, providing around 20 mg per 100 g, which is several times the daily reference intake. This is followed by wheat germ at around 12 mg, liver at around 8 mg, pumpkin seeds at around 7 mg, cooked beef between 5 and 6 mg, and Emmental cheese at around 4 mg. Cooked lentils reach about 1.3 mg.

This raw classification hides the essential: bioavailability is as important as content. Zinc in plants is trapped by phytates, present in whole grains, legumes, and oilseeds, which make it partially unabsorbable. This is why ANSES raises its recommended intake when the diet is rich in phytates. Soaking, germination, and fermentation degrade some of these phytates and improve absorption. A vegan diet therefore combines lower content and reduced absorption: a point to be aware of if you rely on plant proteins or spirulina.

Why should copper be monitored with prolonged supplementation?

This is the most important point on this page, and one of the least written about. Zinc and copper share the same intestinal absorption pathways. A high intake of zinc induces the synthesis of a protein, metallothionein, in intestinal cells, which binds very strongly to copper and retains it; the cell is then eliminated with the renewal of the epithelium. The higher and more prolonged the zinc intake, the less dietary copper is absorbed.

The mechanism is so well established that it is used in medicine for copper overload disease. It also explains why high-dose zinc supplementation continued for months can deplete copper status - a mineral that has its own claims, including "Copper contributes to normal iron transport in the body," from 0.15 mg per serving.

In practice: a few weeks of treatment at usual doses does not pose this problem, but prolonged daily intake at high doses does. Some formulas already combine a little copper for this reason. Long-term use should be discussed with your doctor - the NRV for copper is 1 mg, its European safety limit is 5 mg per day: it does not accumulate either.

Is zinc of interest to athletes?

Two arguments are circulated, one solid, the other overinterpreted.

The solid one: zinc is lost through sweat, and a high volume of training in a hot climate increases these losses. In addition, diets often focus on protein powders and carbohydrates, which are less rich in zinc than a varied plate.

The overinterpreted one: the testosterone claim, which refers to the maintenance of normal levels. There is no evidence to suggest that additional intake increases testosterone in men whose zinc status is already adequate—yet this is the central argument of most ZMA formulas, which combine zinc, magnesium, and vitamin B6. These formulas are consistent, but their benefit lies in covering intake, not in a hormonal action. Our sports nutrition guide explains each category, and mineral losses during exercise primarily involve electrolytes.

What is the dose, and when does it become excessive?

ANSES sets a nutritional reference intake of around 11 mg per day for men and 7.5 mg for women, with higher values when the diet is rich in phytates. The European labeling NRV, on the other hand, is set at 10 mg.

The ceiling is clear: the European upper safety limit is 25 mg per day for adults, from all sources combined — food, supplement, multivitamin, ZMA. This is a limit, not a goal. Many supplements contain between 10 and 15 mg per dose, which is sufficient; products with 50 mg have no justification for over-the-counter use.

Acute excess causes nausea and digestive problems; chronic excess mainly acts through the copper mechanism described above. Medical advice is essential before any supplementation during pregnancy or breastfeeding, in children and adolescents, in cases of kidney failure, when undergoing long-term treatment — zinc reduces the absorption of certain antibiotics, so they should be taken several hours apart — and in cases of chronic pathology. A deficiency is diagnosed by consultation, not on a web page.

Frequently Asked Questions

What is zinc?

A trace element: a mineral that the body needs in very small quantities, around 10 mg per day, but which it cannot produce or store in a readily mobilizable form. It participates in the activity of several hundred enzymes, DNA reading, cell division, and the functioning of the immune system. In a supplement, it is always bound to another molecule — bisglycinate, picolinate, citrate, gluconate, or oxide — and this partner determines the amount actually absorbed.

What are the benefits of zinc?

The only effects a seller is allowed to claim are the European-approved claims listed above: contribution to the normal function of the immune system, normal protein synthesis, maintenance of normal skin, hair, and nails, maintenance of normal testosterone levels, protection of cells from oxidative stress, and a role in cell division. All of these refer to maintenance and normal function: zinc meets a need, it does not push any function beyond normal.

How much zinc per day?

ANSES recommends about 11 mg per day for men and 7.5 mg for women, more when the diet is rich in phytates; the European labeling NRV is 10 mg. The upper safety limit is 25 mg per day for adults, from all sources combined. Most supplements contain between 10 and 15 mg per dose, which is more than enough.

When should I take zinc, morning or evening?

The time of day matters little; the distance from certain foods does. Zinc is better absorbed away from a meal rich in whole grains or legumes, and should not be taken at the same time as a significant source of calcium or iron, which compete with it. On an empty stomach, it causes nausea in some people: bisglycinate is the best-tolerated form. In the evening, away from dinner, works well — which explains the format of ZMA formulas.

Why take zinc?

To ensure adequate intake when the diet provides little: little meat, little seafood, a vegan diet, or a diet very rich in whole grains. Outside of these situations, a varied diet covers the need, and a supplement will not provide anything measurable.

How long should a zinc course last?

One to three months is the usual duration, precisely to avoid the problem of interaction with copper. Beyond that, and especially at high doses, continuous intake should be discussed with a doctor rather than self-renewed.

What are the symptoms of zinc deficiency?

An established deficiency can manifest as more frequent infections, slow wound healing, weakened skin and nails, loss of appetite, or altered taste. These signs are non-specific and found in many other situations: they are not sufficient to draw conclusions. The most exposed profiles are vegan diets, diets very rich in whole grains, and digestive disorders that reduce absorption. A deficiency is confirmed by a medical examination, not by a list of symptoms read online.

Is it dangerous to take zinc?

At usual doses, no. The risk comes from exceeding the 25 mg per day limit from all sources combined. A one-time excess causes nausea, a metallic taste, and digestive problems; prolonged excess depletes copper status, as the two minerals use the same absorption pathways. This is why 50 mg dosages are not justified for over-the-counter use, and daily long-term intake should be discussed with a doctor. Zinc also reduces the absorption of certain antibiotics: space out doses by several hours.

Does zinc affect skin, hair, and nails?

There are three claims—"maintenance of normal skin," "maintenance of normal hair," "maintenance of normal nails"—and they mean exactly what they say: zinc contributes to normal functions. They do not allow for claims of timeliness, improvement, or effect on a skin condition. Skin or hair loss that concerns you should be addressed by a doctor or dermatologist.

What foods contain zinc?

According to the ANSES Ciqual table, oysters are far ahead, at around 20 mg per 100 g, followed by wheat germ at around 12 mg, liver at around 8 mg, pumpkin seeds at around 7 mg, cooked beef between 5 and 6 mg, and Emmental cheese at around 4 mg. Green vegetables provide very little. On the plant side, seeds, oilseeds, legumes, and wheat germ provide most of it – with the caveat of phytates, which retain some of it.

Can zinc and vitamin C be combined?

Yes: no problematic interaction is documented, and both carry the claim "contributes to the normal function of the immune system." This is the logic of formulas that combine them. Just check that you are not accumulating two sources of zinc between a multivitamin, a ZMA, and a dedicated product; our vitamin C section details the available forms.

What is the best zinc?

There is no absolute best zinc, but a simple label guide: the chemical form and the elemental zinc dose per serving must be indicated. "50 mg of zinc gluconate" without zinc content remains ambiguous. For daily intake, chelated forms—bisglycinate in particular—are the best tolerated and least sensitive to phytates; oxide is the cheapest and least well absorbed. Raw materials identified by a brand name also allow you to know what process was used.

What brands can be found in this section?

Our selection is deliberately focused on chelated forms. Nutriting offers a bisglycinate whose raw material is identified by its brand name; IO.Genix covers bisglycinate alone, with the ingredient's origin specified, and two ZMA formulas, one of which is combined with melatonin for evening use; Sinob offers a simple bisglycinate, and Now Foods offers a chelated glycinate. The rest of our micronutrition products are in the magnesium, vitamin D, vitamin B and omega 3 sections, and the complete catalog is under sports nutrition.

Advice in a store near Montpellier?

In our store in Vendargues, about ten minutes from Montpellier, zinc can be compared in thirty seconds: chemical form, elemental dose per capsule, presence or absence of copper. It's also an opportunity to check what your other products already contain, as accumulation is the only real mistake here. We ship everywhere in France and Europe. We will explain what a product does and how to take it; we will not tell you if you are deficient, as that question belongs to your doctor.

Sources: ANSES for nutritional references, Ciqual for food content, EFSA for authorized claims and the upper safety limit.