Influence of dietary zinc and iron on zinc retention in pregnant rhesus monkeys and their infants

To test the idea that zinc uptake may be enhanced in conditions of zinc deficiency, we fed rhesus monkeys diets containing either 4 μg zinc (low-zinc group) or 100 μg zinc (controls) throughout pregnancy and lactation. Each group was divided into two subgroups, one of which received an iron supplement (4 mg ferrous sulfate/kg/day). We investigated iron supplements because excess dietary iron has been suggested to inhibit zinc absorption. ⁶⁵Zn retention from labeled meals was studied in the dams during pregnancy and lactation and in their 10-day-old infants. In both the mothers and the infants, zinc absorption/retention, as measured by whole-body counting, was more than 25% higher in the low-zinc group than in the controls. Iron supplementation had no effect on initial dietary zinc retention, but resulted in a reduction in whole-body ⁶⁵Zn turnover. Thus, changes in zinc status and dietary factors such as iron can affect net retention and turnover of zinc in pregnant and lactating primates fed low-zinc diets.