Safety
Toxicity
Copper toxicity is rare in the general population. Acute copper poisoning has occurred by storing beverages in copper-containing containers, as well as from contaminated water supplies (171). Guideline values for copper in drinking water have been set by the US Environmental Protection Agency (1.3 mg/liter) and by the World Health Organization (2 mg/liter) (172). Symptoms of acute copper toxicity include abdominal pain, nausea, vomiting, and diarrhea; such symptoms help prevent additional ingestion and absorption of copper. More serious signs of acute copper toxicity include severe liver damage, kidney failure, coma, and death.
Of more concern from a nutritional standpoint is the possibility of liver damage resulting from long-term exposure to lower doses of copper. In generally healthy individuals, daily doses of up to 10,000 μg (10 mg) have not resulted in liver damage. The US Food and Nutrition Board has thus set the tolerable upper intake level (UL) in adults at 10 mg/day of copper from food and supplements combined (Table 3) (24). It should be noted that individuals with genetic disorders affecting copper metabolism (e.g., Wilson disease, Indian childhood cirrhosis, and idiopathic copper toxicosis) may be at risk for adverse effects of chronic copper toxicity at significantly lower intake levels. There is some concern that the UL of 10 mg/day might be too high. For example, one study in adult men who consumed 7.8 mg/day of copper for 147 days showed that they loaded excess copper during that time, and some indices of immune function and antioxidant status suggested that these functions were adversely affected by the high intakes of copper (173, 174). However, another study did not report any adverse effects in individuals supplemented with 8 mg/day of copper for six months (150).
| Life Stage (age range) | UL (μg/day) |
|---|---|
| Infants (0-12 months)* | Not established |
| Children (1-3 years) | 1,000 |
| Children (4-8 years) | 3,000 |
| Children (9-13 years) | 5,000 |
| Adolescents (14-18 years) | 8,000 |
| Adults (≥19 years) | 10,000 |
| *Source of intake should be from food and formula only. | |
Drug interactions
Relatively little is known about the interaction of copper with drugs. Penicillamine is used to bind copper and enhance its elimination in Wilson disease, a genetic disorder resulting in hepatic copper overload. Because penicillamine dramatically increases the urinary excretion of copper, individuals taking the medication for reasons other than copper overload may have an increased dietary copper requirement. Additionally, antacids may interfere with copper absorption when used in very high amounts (2). Also, the anti-tuberculosis drug ethambutol may chelate copper in mitochondria and reduce cytochrome c oxidase activity specifically in optic nerve axons, possibly contributing to optic neuropathy which is a documented side-effect of this drug (175).
Linus Pauling Institute Recommendation
The RDA for copper (900 μg/day for adults) is sufficient to prevent deficiency, but the lack of clear biomarkers of copper nutritional status in humans makes it difficult to determine the level of copper intake most likely to promote optimum health or prevent chronic disease. A varied diet should provide enough copper for most people. For those who are concerned that their diet may not provide adequate copper, a multivitamin/mineral supplement will generally provide at least the RDA for copper.
Older adults (>50 years)
Because aging has not been associated with significant changes in the requirement for copper, our recommendation for older adults is the same as that for adults 50 and younger (176).
