Nutrient glossary
What is copper?
Copper works alongside iron to form red blood cells and keeps nerves, immunity and connective tissue in order.
Reviewed 20 July 2026. General information, not medical advice.
The short version
Copper is needed in tiny amounts but for central jobs: loading iron into red blood cells, insulating nerves, building collagen and mopping up free radicals. Deficiency is rare from food alone, though very high zinc supplementation can induce it.
Liver, oysters, nuts, seeds, dark chocolate and mushrooms are the reliable sources; most balanced diets land on target without effort.
Daily reference
1.2 mg a day
The adult reference is 1.2 mg a day.
This is the fixed adult reference used across these pages. In the app, your amount adjusts to your body and way of eating.
Best food sources of copper
Full ranking| Food | Per serving | Per 100g |
|---|---|---|
| Beef Liver | 12.16 mg | 14.3 mg |
| Oysters | 4.85 mg | 5.71 mg |
| Squid (Calamari) | 1.61 mg | 1.89 mg |
| Lobster | 1.55 mg | 1.55 mg |
| Crab | 1.18 mg | 1.18 mg |
| Red Lentils | 0.78 mg | 1.3 mg |
| Sesame Seeds | 0.73 mg | 4.08 mg |
| Cashews | 0.62 mg | 2.2 mg |
Common questions
- Can you get too much copper?
- From food it is very unlikely. Supplements above 5 mg a day long-term are where caution starts.
- Why does high-dose zinc affect copper?
- Zinc and copper share an absorption pathway, so months of high-dose zinc can crowd copper out and cause deficiency.