Copper is a heavy metal that is toxic in the unbound form. Almost all of the copper in the body is bound to proteins, thereby reducing the concentration of unbound copper ions to almost zero. Most diets contain enough copper (2-5mg) to prevent a deficiency and not enough to cause toxicity. The World Health Organization (WHO) suggests that 10-12mg per day may be the upper safe limit for consumption. If as little as 2gms of a copper salt are ingested, usually with suicidal intent, the resulting copper-induced hemolytic anemia and kidney damage are generally fatal.
Copper toxicity is usually due to:
- excessive supplementation
- the increasingly common problem of low levels of zinc in the diet
- contaminated food and drinking water due to contact with metallic copper
- external exposures such as a copper IUD or accidental agricultural overspray
- elevated levels of estrogens.
Since copper and zinc compete with each other for absorption in the gut, copper toxicity has been the subject of greater concern in recent years. This is primarily due to reduced zinc in the diet and the switch from galvanized to copper water pipes. Acidic water such as rain water, left standing in copper plumbing pipes, can be a source of toxicity when consumed. In prolonged contact with copper cooking utensils, an acidic food or beverage can dissolve milligram quantities of copper, sufficient to cause acute toxicity symptoms such as self-limited nausea, vomiting and diarrhea. High copper levels, especially when associated with low zinc levels, have been linked to a variety of symptoms and conditions.
The best means of testing for copper toxicity are 24-hour urine copper or serum ceruloplasmin level tests.