The objective of this study was to determine fractional absorption of exogenous zinc and intestinal excretion of endogenous zinc in women of childbearing age whose habitual dietary zinc intake was marginal. The target population (L group) comprised residents of a remote farming village in northeast China and the control subjects (M group) were residents of Beijing. Mean (+/- SE) calculated dietary zinc intakes were 5.2 +/- 0.2 and 8.1 +/- 0.2 mg/d, respectively. The phytate-zinc molar ratio in the diet of both groups was approximate to 10:1. Zn-70 was administered intravenously before breakfast and Zn-67 orally with three main meals in 1 d. Subsequently, all feces were collected quantitatively until the second visible marker had been excreted and 12-h urine samples were collected on days 3-9. Fractional absorption was determined by measuring cumulative fecal excretion of nonabsorbed Zn-67 and endogenous fecal zinc by an isotope-dilution technique (Zn-70). Fractional absorption values for L and M groups, respectively, were 0.31 +/- 0.03 and 0.34 +/- 0.03 (P = 0.45). Corresponding figures for endogenous fecal zinc were 1.30 +/- 0.07 and 2.34 +/- 0.20 mg Zn/d (P < 0.001). Both the estimated total size of the pools of zinc that exchange with zinc in plasma within 2 d (r = 0.752, P < 0.001) and the excretion of endogenous zinc in the feces (r = 0.706, P < 0.0001) were positively correlated with calculated total daily zinc absorption. We conclude that fractional absorption of zinc does not differ between women consuming marginal and adequate quantities of zinc in their diets, but endogenous zinc is conserved effectively by the intestine in women whose habitual dietary zinc is marginal.