Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2002
Publication Date: 3/1/2003
Citation: HOUSE, W.A., HART, J.J., NORVELL, W.A., WELCH, R.M. CADMIUM ABSORPTION AND RETENTION BY RATS FED DURUM WHEAT GRAIN. BRITISH JOURNAL OF NUTRITION. 2003. v. 89. p. 499-508. Interpretive Summary: Excessive intake of cadmium, a non-essential element, may cause health problems in humans under some conditions. Grain and cereal products, including durum wheat, are sources of dietary cadmium, and this class of foods may account for about 20% of the daily intake of cadmium by the adult population. An international organization has proposed the establishment of fan upper limit to the amount of cadmium that can occur in wheat and still be used as a source of food by people. However, the proposed limit is based on the assumption that 5% of the cadmium in wheat will be absorbed. The present study was conducted with rats to assess the bioavailability of cadmium in durum wheat. Two dietary factors, increased intake of zinc and increased intake of moderate amounts of phytate, a phosphorus-containing compound that occurs in seeds, depressed the bioavailability to rats of Cd that occurred naturally in whole grain durum wheat. In nutritionally replete animals, only about 2.5% of the cadmium in whole grain wheat was absorbed and considerably lowered amounts were retained in the body. Dietary factors that affect mineral bioavailability to rats are likely to have the same effect on mineral bioavailability in human subjects. Moreover, people usually absorb lower amounts of dietary minerals than do animals. Consequently, the amount of cadmium that occurs in durum wheat is not likely to cause health problems in normal people because they probably do not absorb or retain very much cadmium from durum wheat.
Technical Abstract: A whole-body radioassay procedure was used to assess the retention and apparent absorption by rats of cadmium (Cd) in kernels of durum wheat (Triticum turgidum L. var durum) harvested from plants grown hydroponically in 109Cd-labeled nutrient solution. Whole grain wheat labeled intrinsically with 109Cd was incorporated into test meals fed to rats that had been maintained on diets containing either 8, 28 or 101 mg Zn/kg diet and either 0 or 50 g durum wheat/kg diet. The concentration of Cd in the 109Cd-labeled grain was 0.56 mg/kg dry weight and, regardless of diet, all rats consumed about 99% of the test meal offered. In rats fed diets without wheat, Cd absorption averaged 7.7, 4.6 and 2.4% of the dose when the diet contained 8, 28 and 101 mg Zn/kg diet, respectively. When fed diets, containing wheat, Cd absorption averaged 3.8 and 2.6 % of the dose when the Zn concentration was 8 and 28 mg/kg diet, respectively. The amount of Cd retained in the body 15 d postprandial was less than 2% of the dose in all rats, and about 30 to 44 % of the Cd retained in the body was located in the gastrointestinal tract (tissues and contents). In addition to verifying that increased intake of dietary zinc lowers Cd absorption and retention in rats, the study indicates that the bioavailability of Cd in whole grain durum wheat is depressed by whole grain wheat added to the diet.