Marginal nutritional status of zinc, iron, and calcium increases cadmium retention in the duodenum and other organs of rats fed rice-based diets.

Abstract Dietary minerals Zn, Fe, and Ca are antagonistic to Cd absorption. We showed earlier that rats fed a rice-based diet with a marginal content of these nutrients absorbed more Cd than rats fed adequate Zn–Fe–Ca (Environ. Sci. Technol., 36 (2002) 2684–2692). The present experiment was designed to determine the effects of marginal dietary Zn, Fe, and Ca on the uptake and turnover of Cd in the gastrointestinal tract. Two groups of weanling female rats (six per treatment) were fed a diet containing 40% cooked, dried rice containing 0.6 mg Cd/kg. The diet of one group contained adequate Zn (35 mg/kg), Fe (30 mg/kg), and Ca (5000 mg/kg), while that of the other group contained marginal Zn (6 mg/kg), Fe (9 mg/kg), and Ca (2500 mg/kg). Rats were fed for 5 weeks and then orally dosed with 1 g of diet containing rice extrinsically labeled with 109 Cd. From 0.25 to 64 days after dosing, 109 Cd and total Cd concentrations were determined in intestinal segments. Shortly after dosing, 109 Cd, as a percentage of the dose, was about 4 times higher in the duodenum of marginally fed rats than in that of control rats (10% vs 40%, respectively). Sixty-four days after dosing, 109 Cd was 10 times higher in marginally fed rats than in controls; however, of the amount at day 1,