This part of the offering brings together what you can look up: which proteins carry a copper atom, which food categories supply it and in what amounts, what the labeling value of one milligram means, and what an ordinary day of eating looks like once it is added up.
Unlike elements that take part in hundreds of reactions, the list of human copper proteins fits on a single page. They are few in number, well described, and each one sits in a specific location. The overview below lists the enzymes best documented in the scientific literature.
| Protein | Where it is located | What it is responsible for |
|---|---|---|
| Cytochrome c oxidase | inner mitochondrial membrane | transfers electrons to oxygen, forming water |
| Superoxide dismutase 1 | cytosol | converts superoxide into hydrogen peroxide and oxygen |
| Lysyl oxidase | intercellular space of connective tissue | forms the cross-links between collagen and elastin fibers |
| Dopamine-β-hydroxylase | storage vesicle of the nerve terminal | converts dopamine into norepinephrine |
| Ceruloplasmin | blood plasma | oxidizes ferrous iron to ferric iron |
| Tyrosinase | melanosome of the pigment cell | initiates the formation of the pigment melanin |
| Peptidylglycine monooxygenase | secretory vesicle of glandular cells | gives small peptide hormones their final form |
This classification follows standard biochemistry textbooks. Other proteins involving copper are known, but they are less well characterized.
A metal ion in a protein is not an add-on but a structural component. The amino acids surrounding the binding site must be arranged exactly so as to hold the ion in the right geometry. Binding pockets like these do not arise by chance; they are the result of long evolution. That is why copper enzymes are few — and why the ones that exist are not interchangeable in their function.
Two of the proteins listed above underlie claims covered in more detail on the home page: cytochrome c oxidase and lysyl oxidase. A third, dopamine-β-hydroxylase, belongs to nervous tissue.
On food and supplement packaging, a percentage often accompanies the copper content. It refers to 1.0 milligram per day — the nutrition labeling reference value set out in Regulation (EU) No 1169/2011. This number is used to compare products. It is neither a target for any individual nor an upper limit.
In addition, there are numbers from other contexts, which differ because they answer different questions:
All four numbers apply at the same time and do not contradict one another. The labeling value is a calculation figure intended for the label, the estimated value is a recommendation for the population, the adequate intake is an observational figure, and the tolerable upper intake level is a safety threshold.
Moreover, only part of what was on the plate is actually absorbed. This fraction ranges from about one-eighth to more than half and depends on the total amount ingested: when intake is low, the intestinal wall opens more transport pathways; when it is high, it opens fewer.
Lists of individual foods give a false impression of precision: the copper content of the same ingredient varies with the soil, the variety, the harvest year and processing. The food category is more telling. Within a category, values stay within the same order of magnitude, while between categories the differences reach a factor of a hundred or more.
| Category | Copper per 100 g | Examples from the category |
|---|---|---|
| Organ meats | 3.0–14.0 mg | Calf liver, beef kidney |
| Oilseeds | 1.2–4.5 mg | Sesame, poppy seeds, Brazil nuts |
| Crustaceans and shellfish | 1.0–4.5 mg | Oyster, lobster, mussel |
| Cocoa products | 1.0–4.0 mg | Cocoa powder, dark chocolate |
| Legumes, dried | 0.60–1.00 mg | Chickpeas, soybeans, white beans |
| Whole grains | 0.25–0.55 mg | Buckwheat, cracked rye, pearl barley |
| Mushrooms and vegetables | 0.05–0.50 mg | White button mushroom, kale, beet |
| Fresh fruit | 0.02–0.15 mg | Avocado, blackberry, apricot |
| Dairy products | 0.01–0.05 mg | Drinking milk, plain yogurt, semi-hard cheese |
Ranges from published food composition tables, rounded. Some products may fall above or below their category.
Two observations stand out. First, plant-based categories provide most of the usual intake, even though the highest individual values come from animal sources — simply because oilseeds, legumes and whole grains appear on the plate more regularly than liver. Second, dairy products contribute practically nothing to this calculation; that is why copper supply in infants is examined separately.
The categories only turn into a meaningful number once a concrete day is added up. The overview below is neither a meal plan nor a recommendation, but a calculation exercise: five ordinary items, valued at the average figures of their respective categories.
| Time | Item | Amount | Copper |
|---|---|---|---|
| morning | Buckwheat porridge, dry weight | 60 g | 0.31 mg |
| morning | Toasted sesame, sprinkled on top | 15 g | 0.62 mg |
| noon | Chickpea stew, dry weight | 70 g | 0.60 mg |
| afternoon | Dark chocolate, 70 % cocoa | 20 g | 0.24 mg |
| evening | White button mushrooms, pan-fried | 150 g | 0.53 mg |
| Daily total | 2.30 mg | ||
Rounded averages. Only a fraction of this is absorbed; see the section on reference values.
2.30 milligrams is well above the labeling value of 1.0 milligram, as well as the estimated value from professional societies. At the same time, it remains far below the tolerable upper intake level of 5 milligrams. So the day is neither borderline nor remarkably high — above all, it shows how quickly two or three copper-rich items add up to several times the label value.
If you recalculate the same day without the sesame and without the chocolate, 1.44 milligrams remain. This is precisely what shows why no statement about a particular person's intake can be derived from tables alone: here, two small items account for nearly forty percent of the daily value.
The three claims covered on this page, unchanged and without additions. Any rewording is prohibited, even if the meaning is equivalent.
The list of authorized claims contains more entries for copper than the three cited here. Only what relates to the subject of this page is reproduced: the proteins in which the metal is incorporated. The claims not covered here are no less valid — they simply fall outside this subject.
From the origin of the sample and the measurement method. A grain grown in mineral-poor sandy soil contains less than the same grain grown in heavy clay soil. Added to this are differences between varieties, storage time and whether the measurement was taken raw or cooked. That is why the table on this page works with ranges rather than single decimal values.
That does happen, and this copper is not included in the table values, because it depends on the household plumbing and cookware, not on the food. The regulations on water intended for human consumption set a limit of 2 milligrams per liter in this regard. Anyone who wants to know precisely can obtain the local value from their water utility.
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Yes, especially in depth on the supporting evidence: for each table row, the source and the year of the survey, the full calculation behind the sample day, as well as explanations of the reference values. It contains no new or expanded health claims — it sticks to the three statements reproduced above.
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