endogenous losses was used to estimate obligatory losses in healthy people (Turnlund et al., 1997, 1998). When copper intake was 380 μg/day, copper status declined significantly. Endogenous fecal losses were calculated to be 240 μg/day, slightly higher than the estimate from TPN data (Shike et al., 1981), and urinary losses were less than 20 μg/day. A careful study of surface copper losses in men reported that these averaged 42 μg/day (Milne et al., 1991). Other losses, such as hair, nails, semen, or menstrual, have not been measured, and it is assumed they are similar to surface losses. Therefore the amount of absorbed copper needed to replace obligatory losses is 344 μg/day (240 + 20 + 42 + 42). Copper absorption at this level of intake is approximately 75 percent. Therefore, 460 μg/day of dietary copper would be the minimum amount required to replace obligatory losses. Endogenous fecal copper was 50 μg/day higher at 380 μg/day than at 460 μg/day, and so 50 μg/day was added to endogenous fecal losses to account for the increase that occurs between 380 and 460 μg/day. Thus 510 μg/day (460 + 50) of dietary copper is required to replace copper losses from all sources and to achieve zero balance. Estimation of the average requirement based on indicators of copper status is similar to, but slightly higher than, the average requirement determined by the factorial approach. The EAR is based on biochemical indicators of copper status of men and women, and there was no basis for a difference in requirement based on gender. There are no data on which to base an EAR for older adults, and no evidence to suggest that the requirements would be different.

The data available to set an EAR are limited for men and women, as well as the number of levels of dietary copper in depletion/repletion studies. Thus, a CV of 15 percent is used. The RDA is defined as equal to the EAR plus twice the CV to cover the needs of 97 to 98