Copper is a naturally occurring metal that serves as a trace mineral essential for human health. The body requires copper to support numerous biological processes, but it cannot produce this element internally, making consistent dietary intake mandatory. While the total amount needed is small, finding concentrated food sources is important for meeting the daily requirement. This mineral acts as a co-factor for various enzymes, helping activate them to perform their jobs across the body.
Essential Functions of Copper in the Body
Copper plays a direct role in the body’s energy production system within the mitochondria of cells. It is a component of the enzyme cytochrome c oxidase, which is responsible for the final step of converting oxygen into water, a reaction that generates the majority of cellular energy in the form of Adenosine Triphosphate (ATP). This mineral is also involved in iron metabolism, facilitating the proper utilization of iron throughout the body. Copper-dependent enzymes, such as ceruloplasmin, oxidize iron to allow it to bind to its transport protein, transferrin, enabling iron to be moved for red blood cell formation.
The mineral helps protect cells from damage by contributing to the body’s antioxidant defense system. Copper is a component of superoxide dismutase, an enzyme that disarms harmful free radicals that are byproducts of cellular metabolism. Copper is also required for the formation of connective tissues like collagen and elastin. The enzyme lysyl oxidase, which depends on copper, cross-links these fibers to provide strength and flexibility to the skin, bones, and blood vessels.
The Absolute Best Dietary Sources of Copper
The most concentrated sources of copper come from animal products, particularly organ meats and certain shellfish. Beef liver is the richest source, with a standard three-ounce serving of pan-fried liver containing 12,400 micrograms (mcg) of copper, significantly more than the daily requirement. A three-ounce serving of cooked Eastern oysters provides approximately 4,850 mcg of copper, establishing shellfish as another primary source.
A second category of excellent sources includes nuts, seeds, and dark chocolate. One ounce of dry-roasted cashews provides about 629 mcg of copper, while the same serving size of sunflower seeds contains around 519 mcg. Dark chocolate is a potent source, with a 3.5-ounce bar containing 70–85% cocoa solids delivering up to 1,770 mcg of copper.
Third-tier sources offer good amounts of copper and are more commonly consumed in a typical diet. Whole grains and legumes contribute notable amounts, with products like wheat-bran cereals and lentils being reliable choices. Certain vegetables also contain copper, such as potatoes, where one medium cooked potato with the skin on offers about 675 mcg. Cooked shiitake mushrooms are another excellent plant-based source, providing around 650 mcg per half-cup serving.
Balancing Intake: Deficiency, Requirements, and Toxicity
The Recommended Dietary Allowance (RDA) for copper in adults, age 19 and older, is 900 mcg per day. This amount is generally sufficient to prevent deficiency and support normal bodily functions. Average dietary intake in the United States often meets or exceeds this level for most adults.
Copper deficiency is uncommon in healthy individuals who consume a varied diet, but it can occur due to specific circumstances. Conditions that cause nutrient malabsorption, such as celiac disease or a history of gastric bypass surgery, can impair copper uptake. Excessive intake of zinc supplements is another cause, as high doses of zinc interfere with the absorption of copper in the small intestine. Signs of deficiency can include anemia that is unresponsive to iron supplementation, fatigue, increased risk of infection, and neurological problems like numbness or tingling.
Toxicity is rare from food sources alone, but it is possible with excessive supplementation or in the presence of certain genetic disorders. The Tolerable Upper Intake Level (UL) for copper in adults is set at 10,000 mcg (10 milligrams) per day from all sources. Consuming amounts above this level consistently is a risk factor for liver damage. A genetic condition called Wilson’s disease prevents the body from properly excreting excess copper, leading to accumulation in organs like the liver and brain. Acute toxicity symptoms include severe abdominal pain, nausea, and vomiting.