The data available to set an EAR are limited for men and women, as is the number of levels of dietary copper in the depletion/repletion studies. Thus, a CV of 15 percent is used because information is not available on the standard deviation of the requirement for lactating women. The RDA is defined as equal to the EAR plus twice the CV to cover the needs of 97 to 98 percent of individuals in the group (therefore, for copper the RDA is 130 percent of the EAR). The calculated RDA is rounded to the nearest 100 μg.

Copper is widely distributed in foods. The accumulation of copper in plants is not affected by the copper content of the soil in which they grow. Organ meats, seafood, nuts, and seeds are major contributors of dietary copper (Pennington et al., 1995). Wheat bran cereals and whole grain products are also sources of copper. Foods that contribute substantial amounts of copper to the U.S. diet include those high in copper, such as organ meats, grains, and cocoa products, and those relatively low in copper that are consumed in substantial amounts, such as tea, potatoes, milk, and chicken.

Data from nationally representative U.S. surveys are available to estimate copper intakes (Appendix Tables C-15, C-16, D-2, E-3). The median intake of copper for women is approximately 1.0 to 1.1 mg/day, whereas the median intake for men ranges from 1.2 to 1.6 mg/day (Appendix Tables C-15 and D-2).