The effect of wheat bran on the absorption and accumulation of cadmium in rats

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Abstract
1. The major purpose of the present study was to determine whether the addition of wheat bran to endosperm crisp bread in a composite diet given to rats for 6 weeks causes an increase in the accumulation of cadmium in the rats due to the Cd content in the bran, or whether binding factors in the bran, such as dietary fibre and phytic acid, reduce or prevent the accumulation of this Cd. A second purpose was to determine whether the accumulation of Cd can be estimated by measuring the absorption of 199Cd given in a single meal of the diet.2. Three groups of eight rats were fed on one of three diets. Half of each diet consisted of a basal mixture of starch, protein, oil, minerals and vitamins. The remainder consisted of crisp breads based on refined wheat flour (endosperm group), wheat flour + bran in equal amounts (bran group) and wheat flour + Cd to give a Cd content similar to that of the bran group (endosperm + Cd group). After 41 d on the diets, the rats were deprived of food but not water for 12 h and then given a 5 g test meal of their respective diets with 109Cd added. After 3 h the remaining 109Cd-labelled diets were replaced with the unlabelled diets for 3 h before the rats were killed.3. The total Cd contents in the wall of the proximal small intestine, including mucus, and in the liver and kidneys were highest in the endosperm + Cd group and lowest in the endosperm group. The amounts of Cd in the intestinal wall, including mucus, and in the liver and kidneys which derived from the test meal (calculated from 109Cd accumulation) were significantly higher in the endosperm + Cd group than in either of the other two groups. The concentration of Cd in the organs of the bran group which derived from the test meal was not significantly greater than that in the endosperm group.4. The individual variation in Cd content in the liver and kidneys make it very difficult to demonstrate differences in Cd accumulation from the relatively low, naturally occurring Cd concentrations in the diets. Differences in the absorption of 109Cd from test meals indicate that very little of the Cd in bran is available for absorption.