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How can high doses of iron or copper become toxic?

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USDA MyPlate dietary guidelines — human nutrition MyPlate, a revised set of dietary guidelines introduced by the U.S. Department of Agriculture (USDA) in 2011, divides the four basic food groups (fruits, grains, protein, and vegetables) into sections on a plate, the size of each section representing the relative dietary proportions of each food group. The small blue circle shown at the upper right illustrates the inclusion and recommended proportion of dairy products in the diet.

In the context of human physiology, toxicity from iron and copper typically arises not from standard dietary intake, but from specific metabolic disorders or excessive supplementation.1

Iron Toxicity

The body has a limited capacity to excrete iron, making it susceptible to accumulation. Toxicity generally occurs in two ways:2
* Genetic and Medical Factors: Individuals with hereditary hemochromatosis possess a metabolic defect that causes the body to overabsorb iron. Similarly, patients receiving repeated blood transfusions may experience dangerous iron buildup. This excess iron deposits in tissues, leading to severe damage in organs such as the liver and heart.13
* Supplementation: High-dose iron supplements pose a significant poisoning risk, particularly to young children. While a daily intake of up to 45 mg is generally considered low risk, exceeding this through supplements can cause gastrointestinal distress and acute toxicity.14

Copper Toxicity

Copper toxicity is rare and unlikely to result from diet alone. It is primarily associated with Wilson disease, a rare hereditary disorder where a defective gene (ATP7B) prevents the proper transport and excretion of copper. This causes copper to accumulate in the liver and brain, leading to progressive tissue damage and neurological symptoms.15