Copper

What it does and why you need it

Copper sits at the active site of several enzymes including cytochrome c oxidase (in mitochondria, for energy), ceruloplasmin (for iron transport), and superoxide dismutase (for antioxidant defence). Deficiency is uncommon in healthy adults, but the zinc interaction is well documented and is the most relevant practical point in UK supplement use.

Best food sources

Values per 100g from USDA SR Legacy and McCance and Widdowson 7th edition; the site's food entries currently store macros only.

Copper in common UK foods, ranked by amount per typical portion. Per-100g values from USDA / M&W. Percentages against the 1.2mg adult RNI.
FoodTypical UK portionCopper per portion% adult RNI
Oysters, cooked100garound 4mg or moreover 300%
Cashew nuts30garound 0.7mg58%
Dark chocolate, 70%+ cocoa
(not currently in the site's food encyclopedia)		20g (two small squares)around 0.35mg29%
Tahini15g (one tablespoon)around 0.25mg21%
Mushrooms, cooked80garound 0.4mg33%
Lentils, cooked150garound 0.4mg33%

UK reference intake by age and sex

UK Reference Nutrient Intake (RNI) for copper is set by SACN (1991).

UK copper RNI by age and life stage (SACN, 1991)
GroupDaily copper (mg)
Babies, 0 to 12 months0.3
Children, 1 to 3 years0.4
Children, 4 to 6 years0.6
Children, 7 to 10 years0.7
Children, 11 to 14 years0.8
Adolescents, 15 to 18 years1.0
Adults, 19 years and over1.2
PregnancyNo increment
Breastfeeding1.5 (an increment of 0.3)

Deficiency signs and who is at risk

Copper deficiency from diet alone is uncommon. It is mostly seen as a result of:

  • Long-term high-dose zinc supplementation (over about 50mg per day for months).
  • Malabsorption conditions (coeliac disease, Crohn's, ulcerative colitis, after bariatric surgery).
  • Long-term proton pump inhibitor use.
  • Rare inherited conditions (Menkes disease).

Signs include anaemia (that does not respond to iron, because copper is needed to use iron properly), low white cell count, bone changes, and in long-running cases nerve damage.

Too much: safe upper limit

Copper from food is not a concern. NHS supplement guidance: 10mg or less of copper a day from supplements is unlikely to cause any harm.

Very high copper intake (rare from food, sometimes from contaminated water pipes or supplement overuse) can cause stomach pain, nausea, vomiting, and liver damage. Wilson's disease, a rare inherited copper-handling disorder, requires copper avoidance under specialist care.

Supplements and UK guidance

Routine copper supplementation is not needed for healthy UK adults. The food supply covers requirements.

If you are taking a long-term high-dose zinc supplement (over about 25 to 50mg per day), check whether a small amount of copper (around 1 to 2mg) is included; many balanced products do this to prevent copper deficiency. Discuss with a GP or pharmacist if uncertain.

Related

  • The zinc-copper balance: Zinc. High-dose zinc reduces copper absorption.
  • Iron handling: Iron. Copper is part of the iron transport machinery; copper deficiency can cause an iron-resistant anaemia.
  • Best food sources: Oyster, Cashew nuts, Mushrooms, Lentils.

Sources and references

  • NHS. Vitamins and minerals: Others. nhs.uk/conditions/vitamins-and-minerals/others.
  • SACN. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Department of Health Report 41 (1991).
  • Public Health England. McCance and Widdowson's The Composition of Foods, 7th summary edition (2015).

This page is reference information for UK shoppers. It is not medical advice.