Iron Transport in the Body —
The Role of Copper

How does iron reach the places where it is needed?

Iron is one of the best-known trace elements in the human body. It is a component of haemoglobin and enables oxygen transport in the blood. But iron alone is not enough — for it to travel from food into the cells, complex transport mechanisms are required, and other trace elements take part in them.

Iron transport describes the path of iron from absorption in the small intestine, through transfer into blood plasma, to distribution to target tissues such as bone marrow, liver, and muscle. Along this path, iron must repeatedly change its oxidation state — from the divalent (Fe²⁺) to the trivalent form (Fe³⁺) and back. These conversions require enzymes that depend on certain minerals as cofactors.

The European Food Safety Authority (EFSA) has produced scientific opinions on the contribution of copper to iron transport. On this basis, the EU Commission has published an authorised health claim.

Why iron transport matters to the organism

Iron is involved in a wide range of physiological processes. Without functioning transport, supplying the tissues with this trace element would not be possible. In detail, this concerns:

• Oxygen supply: Haemoglobin in erythrocytes binds oxygen in the lungs and releases it again in the tissues. This cycle requires a steady supply of iron.
• Energy metabolism: Iron is a component of the cytochromes in the mitochondrial respiratory chain, which is responsible for ATP production.
• Myoglobin: In muscle, myoglobin serves as an oxygen store and likewise contains an iron centre.
• Immune defence: Certain immune cells require iron for their proliferation and antimicrobial activity.
• DNA synthesis: The enzyme ribonucleotide reductase, which takes part in DNA synthesis, is an iron-dependent enzyme.

As the body has no active excretion mechanism for iron, iron homeostasis is controlled mainly through the regulation of uptake and intracellular transport. Daily iron losses via the skin, intestinal epithelium, and minor bleeding amount to roughly 1–2 mg and must be replaced through the diet.

The role of copper: ceruloplasmin and hephaestin

Copper fulfils its function in iron transport via two key enzymes. Ceruloplasmin, which circulates in blood plasma, is a multicopper ferroxidase that oxidises Fe²⁺ into Fe³⁺. Only in the trivalent form can iron bind to the plasma protein transferrin, which transports it to the target tissues.

Hephaestin, a membrane-bound homologue of ceruloplasmin, is located in the enterocytes of the small intestine. It catalyses the same oxidation reaction and thereby enables the export of iron from the intestinal cells into the blood. Both enzymes are copper-dependent — where copper intake is insufficient, their activity is limited.

Under EU regulation, the following authorised claim applies:

„Copper contributes to normal iron transport in the body“ — In accordance with Regulation (EU) No 432/2012

Copper in the diet

Copper is found in numerous foods. Particularly rich in copper are organ meats (especially liver), shellfish, nuts, seeds, legumes, and whole grain products. Dark chocolate and certain vegetables such as potatoes and mushrooms also provide notable amounts. The reference value for daily copper intake is 1 mg under EU Regulation 1169/2011.

The bioavailability of copper from food is usually between 30 % and 60 %. It is influenced, among other things, by the simultaneous consumption of zinc, vitamin C, and phytic acid, as these substances can compete with copper for absorption in the small intestine.