have been reported to result from zinc supplementation of pregnant African-American women whose baseline dietary zinc intake was calculated to be 13 mg/day (Goldenberg et al., 1995). This calculated dietary zinc intake is notably high in comparison with other data for African-American women (Mares-Perlman et al., 1995). Without additional supporting documentation, it is difficult to reconcile the implications of the results of this study (with respect to dietary zinc requirements during pregnancy) with the EARs derived from a factorial approach. Nor is it easy to reconcile these findings with the results of other intervention studies. For example, no effect of zinc supplements on birth size was observed in a recent large-scale study of Peruvian women whose dietary zinc intake was estimated to be 7 mg/day (Caulfield et al., 1999b). There was, however, evidence of improved fetal neurobehavioral development (Merialdi et al., 1998).

A report that zinc intakes of less than 7.5 mg/day during the third trimester are associated with lower zinc concentrations in human milk is consistent with the EAR (Ortega et al., 1997).

The RDA for zinc is set by using a CV of 10 percent (see Chapter 1) because information is not available on the standard deviation of the requirement. The RDA is defined as equal to the EAR plus twice the CV to cover the needs of 97 to 98 percent of the individuals in the group (therefore, for zinc the RDA is 120 percent of the EAR). The calculated RDA is rounded to the nearest 1 mg.

Losses in Human Milk. Average concentrations of zinc in human milk decline physiologically from approximately 4 mg/L at 2 weeks