Dietary Sources of Copper

Aside from a few select sources, most foods contain between 2 and 6 mg Cu kg^-1 dry mass (120). Of the 218 core foods tested, 26 provided 65% of the required copper intake (121). This list included high copper-containing foods such as beef liver and oysters that are consumed infrequently and low copper-containing foods such as tea, potatoes, whole milk, and chicken, which are consumed frequently enough to be considered substantial dietary sources of copper (121). Whole fruits and vegetables contain 20 to 370 mg Cu kg^-1; dairy products, including whole milk, contain 3 to 220 mg Cu kg^-1; beef, lamb, pork, and veal contain 12 to 9310 mg Cu kg^-1; poultry contains 11 to 114 mg Cu kg^-1; and seafood and shellfish contain 11 to 79,300 mg Cu kg^-1, with cooked oysters having the maximum value (121). Although dietary copper varies regionally, geographically, and culturally, a balanced diet appears to provide an adequate intake of copper for most people. In some areas, additional daily intake of copper can be obtained from drinking water transmitted through copper pipes. In the United States, the current EPA limit for copper in drinking water is 1.3 mg L^-1 (122). In developed and developing countries, adults, young children, and adolescents, who consume diets of grain, millet, tuber, or rice, along with legumes (beans), small amounts of fish or meat, some fruits and vegetables, and some vegetable oil, are likely to obtain enough copper if their total food consumption is adequate in calories. In developed countries where consumption of red meat is high, copper intake is also likely to be adequate (120).

Forage material containing 7 to 12 mg Cu kg^-1 dry weight is considered a desirable range for most grazing ruminant animals (123). The copper content of Chinese leymus (Leymus chinesis Tzvelev), needlegrass (Stipa grandis P. Smirnow), and fringed sage (Artemisia frigida Willd.) on grasslands of Inner Mongolia ranged from 0.8 to 2.3 mg kg^-1 dry matter, and this content was concluded to be severely deficient in copper for ruminant animals (124). The majority of mountain pasture plants examined in central southern Norway were unable to provide enough copper (28). Neonatal ataxia or ‘swayback’ is typical of copper deficiency in young lambs, and ‘steely’ or ‘stringy’ wool is a deficiency symptom in adult sheep (124).