This page summarises what is documented about copper in nutritional science — from absorption in the duodenum to the four claims that the European Commission has authorised for this trace element. The figures come from the reference values of the EU Food Information Regulation and from the nutrition tables of the professional bodies.
Copper reaches the body exclusively through food. Unlike vitamin D, there is no synthesis pathway in the organism, and unlike iron, there is no large depot from which the body could draw for months. Daily intake and excretion via the bile are therefore closely related.
Most dietary copper is absorbed in the duodenum and upper jejunum. The membrane protein CTR1 is mainly responsible, transporting monovalent copper ions into the intestinal cell. Divalent copper must first be converted into the monovalent form by a reductase at the cell surface.
Inside the cell, chaperones take over onward delivery: ATOX1 brings copper to the ATPase ATP7A in the Golgi membrane, CCS supplies superoxide dismutase, and COX17 the mitochondria. This division of labour ensures that hardly any copper ion is present unbound in the cytoplasm.
The proportion of copper actually absorbed varies considerably with the amount supplied. At low intakes the intestine absorbs up to 50 percent; at very high intakes the proportion falls below 15 percent. This adjustment is the most important mechanism by which the body keeps its copper content in balance.
Particularly rich in copper are offal, shellfish, nuts, seeds, pulses and cocoa products. The following values are averages and vary with origin, variety and preparation:
| Food | Copper per 100 g |
|---|---|
| Calf liver | approx. 5.5 mg |
| Oyster | approx. 3.6 mg |
| Cocoa powder, highly defatted | approx. 3.8 mg |
| Cashew nuts | approx. 2.2 mg |
| Sunflower seeds | approx. 1.8 mg |
| Lentils, dried | approx. 0.7 mg |
| Rolled oats | approx. 0.5 mg |
| Wholegrain bread | approx. 0.3 mg |
Sources: nutrition tables of the German-language nutrition societies, as of 2025.
Several components of food influence how much copper passes from the intestine into the blood. Phytic acid from wholegrain cereals and pulses binds copper ions and reduces their availability; soaking, sprouting and sourdough fermentation lower the phytate content noticeably.
A permanently very high zinc intake works in the same direction, because it increases the formation of metallothionein in the intestinal cells. This protein binds copper more tightly than zinc, so that a larger share is excreted again with the shed intestinal mucosa. With a normal mixed diet this effect is irrelevant.
Organic acids from fruit and vegetables, on the other hand, have a favourable effect on availability, as does animal protein, whose amino acids histidine and cysteine serve as binding partners for copper.
Anyone who studies iron sooner or later comes across copper. The reason is a single protein: ceruloplasmin, formed in the liver, coloured blue by its six bound copper atoms and the source of the old name “blue protein of the plasma”.
In food and in the body's stores, iron is predominantly divalent. The transport protein transferrin, however, binds only trivalent iron. Ceruloplasmin closes this gap: as a ferroxidase it transfers electrons from iron to oxygen and thereby converts it into the transportable form.
A second, membrane-bound enzyme with the same task is hephaestin. It sits in the basolateral membrane of the intestinal cells and works directly at the point where iron leaves the cell via the exporter ferroportin. Both enzymes belong to the family of multicopper oxidases.
Under Regulation (EU) No 432/2012
It should be noted that ceruloplasmin in the blood also rises as an acute-phase protein. An elevated measurement alone therefore says little about copper supply — interpreting it belongs in medical hands.
The brain is among the tissues with the highest copper concentration. Two circumstances explain this: the extraordinary energy turnover of nerve cells and a series of enzymes that cannot carry out their reaction without copper in the active centre.
Dopamine β-hydroxylase sits in the storage vesicles of sympathetic nerve endings. It attaches a hydroxyl group to the dopamine molecule and turns it into noradrenaline. For this step it needs two copper atoms per subunit as well as ascorbate as an electron donor.
A related reaction is catalysed by peptidylglycine α-amidating monooxygenase, which converts numerous neuropeptides into their biologically active form in the first place. The formation of the myelin sheaths, the insulating layer around the nerve fibres, is also accompanied by copper-dependent reaction steps.
Under Regulation (EU) No 432/2012
Every cell that consumes oxygen produces superoxide radicals in the process. They arise as a by-product at the respiratory chain and react with almost anything they reach. The organism keeps them in check with an enzyme system whose first step is copper-dependent.
The cytosolic superoxide dismutase, SOD1 for short, carries one copper and one zinc atom per subunit. The copper ion performs the actual catalysis: it switches between the monovalent and divalent state and in doing so converts two superoxide molecules into oxygen and hydrogen peroxide. The zinc atom stabilises the structure of the enzyme.
The hydrogen peroxide that forms is then broken down further by catalase and glutathione peroxidase. Copper thus stands at the beginning of a chain that ends in water and oxygen. A second variant of the enzyme, the extracellular SOD3, also carries copper and acts in connective tissue and in the vessel wall.
Under Regulation (EU) No 432/2012
The last complex of the respiratory chain, cytochrome c oxidase, is at the same time the largest copper-containing enzyme complex in the human body. It receives electrons from cytochrome c and transfers them to molecular oxygen, which is reduced to water in the process.
The enzyme has two copper-containing centres, designated Cu₀ and Cuᷟ. Cu₀ takes up the electrons; Cuᷟ, together with a heme iron, passes them to oxygen. The energy released in the process drives protons across the inner mitochondrial membrane and builds up the gradient from which ATP synthase obtains adenosine triphosphate.
Around 90 percent of the cell's energy requirement is met by this route. Heart muscle, skeletal muscle and brain accordingly contain many mitochondria and therefore a great deal of cytochrome c oxidase.
Under Regulation (EU) No 432/2012
For labelling purposes, the Nutrient Reference Value is decisive in the EU. Alongside it, the professional bodies and EFSA give their own estimated or guideline values:
| Reference figure | Value per day | Note |
|---|---|---|
| NRV, Regulation (EU) No 1169/2011 | 1.0 mg | Basis of the percentage on labels |
| Estimated value, adults (D-A-CH) | 1.0–1.5 mg | Range for an adequate intake |
| EFSA, adequate intake, women | 1.3 mg | Adequate Intake, 2015 opinion |
| EFSA, adequate intake, men | 1.6 mg | Adequate Intake, 2015 opinion |
| Tolerable upper level, adults | 5.0 mg | Upper level for total intake |
The values apply to healthy adults. Children, pregnant women and breastfeeding women have different reference figures.
Because 1.0 mg is the reference value for nutrition labelling laid down in Regulation (EU) No 1169/2011. A dose of this size gives a neat 100 percent of the reference value on the label. The figure is a labelling quantity and not an individual recommendation.
In households with copper plumbing, tap water can contain measurable amounts, especially after the water has stood in the pipe for a long time. The German Drinking Water Ordinance limits the content to 2 mg per litre. Anyone who wants to know their own value can have a sample tested by an accredited laboratory.
Both compounds are listed in Annex II of Directive 2002/46/EC as permitted copper sources for food supplements, as are copper citrate, copper carbonate and copper lysine complex. They differ in the copper content per gram of substance and in solubility. The quantity stated on the pack always refers to the element contained, not to the salt.
Only the officially prescribed wording, or a formulation with the same meaning for the consumer, is permissible. The approved version reads: “Copper contributes to normal iron transport in the body” — Under Regulation (EU) No 432/2012. In addition, the mandatory notices on a balanced diet and a healthy lifestyle must appear on the packaging.
Because both trace elements partly use the same binding partners in the intestinal wall, and because they sit side by side in the enzyme SOD1. The authorised claims are unaffected by this: each claim belongs to exactly one mineral and rests on its own opinion. This page is about copper alone.
The complete guide goes deeper into every section of this page and adds worked examples for daily intake, an extended food table and the sources of the opinions cited.
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