Trace element 29 · 2026 text edition
Chromitpfad follows a single iron atom from the membrane that lets it out to the pocket that receives it — and sets alongside it the one sentence the European Union has authorised for copper on the subject.
To the guidanceIn the register of health claims authorised in the European Union stands a wording that puzzles on first reading: it is assigned to the element copper but speaks of iron. The reason lies not in the language of the legal text but in the chemistry of a single reaction step.
Iron does not move through the body as a free particle. It is passed from protein to protein, and at one point in this chain its oxidation state changes. This transition is handled by an enzyme whose active site carries copper atoms. If the step were absent, the metal would lie where it had just left the cell.
Chromitpfad describes this section in the language of biochemistry and, separately from it, carries the sentence the European Commission has authorised for copper. The two levels are kept apart in this text: one part is reported specialist literature, the other an official assessment, and neither of them supports the other.
A few nanometres lie between the interior of a cell and the blood plasma. Over this short stretch something happens to the iron that can be described neither as transport nor as storage: it gives up an electron. Only afterwards does it fit into the binding site that carries it onward.
On the blood-facing side of the gut cell sits a membrane protein listed in the specialist literature as the only known exit for iron from a mammalian cell. It moves the metal outward in the divalent form, that is, as it was present inside the cell. The same design is found in the phagocytes of the spleen and liver, which move far larger amounts than the intestinal wall.
What arrives on the outside is therefore chemically incompatible. The protein that passes iron along in the plasma accepts only the trivalent form. Between exit and uptake there is thus a step bridged not by movement but by a reaction.
The enzymes that carry out this step belong to the group of multicopper oxidases. Their construction follows a recurring pattern: a single, standalone copper atom that gives the purified protein its blue colour in concentrated solution, and alongside it a cluster of three further copper atoms. The single atom receives one electron at a time from the iron and passes it on within the protein; the trio collects four such electrons and hands them to an oxygen molecule, from which two water molecules then emerge.
Two versions of this design are described in humans: one dissolved in blood plasma, one anchored in the cell membrane. Both perform the same conversion at different locations, and both lose their activity as soon as the metal is removed — a finding from experiments on isolated protein, not on living tissue.
Looked at in figures, food is not the main source. An adult takes in about one to two milligrams of iron a day through the gut; at the same time phagocytes break down so many aged red blood cells that twenty to twenty-five milligrams are released from them and handed back to the circulation. The charge step therefore concerns not primarily the route from plate to blood but an internal circulation that continues without any input from outside.
It is precisely at this that the only line the European register carries for this element and this process is aimed. It is tied to copper and cannot be reworded without leaving its scope. Its wording:
„Copper contributes to normal iron transport in the body“ — Under Regulation (EU) No 432/2012
Presentation per cell biology and biochemistry literature. The turnover figures describe orders of magnitude and make no statement about the condition of any individual person.
Four cards, each with a subject of its own. Only the first carries an authorised claim; the other three are descriptive text with no health-related content.
An adult carries a total of about 70 to 120 milligrams of copper, distributed across liver, brain, musculature and blood. Freely dissolved, the metal is practically absent: it sits in binding proteins or in the active sites of enzymes. One of these enzymes ensures that iron, after leaving a cell, passes into the form the blood's transport protein accepts.
Under Regulation (EU) No 432/2012
As far as is described, iron leaves a body cell through a single membrane protein by the name of ferroportin. It occurs in the intestinal wall just as it does in the phagocytes of spleen and liver. Both cell types release the metal in the same divalent form in which it is present inside — regardless of whether it comes from a meal or from the breakdown of red blood cells.
A description of a transport route. There is no authorised EU claim for this individual step.
Transferrin, which passes iron along in the plasma, takes up two atoms per molecule. Each of the two pockets binds the metal in trivalent form and always together with a carbonate ion, which alone closes the binding. No room is provided there for the divalent form; it would not let the pocket close in the first place.
Structural detail per protein chemistry literature, with no reference to a state of health.
The line quoted concerns copper alone, even though a second element appears in its wording. It describes a process, not a finding. What it says about diseases is nothing: neither about their onset nor about their course, and no such statement can be wrung from it. It may moreover be used only for products containing an amount of the element that is significant within the meaning of nutrition labelling.
The written-out version follows the same iron atom three stations further: to the receptor of the target cell, to the return of the unloaded transport protein, and to the methods by which the activity of the copper-containing oxidase in plasma can be quantified. Added to that are the content tables at full width, the register extract in its official wording and, for each section, a source line with year and reference.
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