Mineral status of female rats affects the absorption and organ distribution of dietary cadmium derived from edible sunflower kernels (Helianthus annuus L.)

The intake of food cadmium (Cd) in microg/day over time can increase the body burden of this element. Some human populations that consume subsistence rice-based diets low in calcium (Ca), iron (Fe), and zinc (Zn) are more susceptible to Cd poisoning than populations that consume more nutritious diets. This study determined the effects of marginal deficiencies of these essential elements on the absorption and organ retention of Cd from a natural food that contains Cd, edible sunflower kernels (Helianthus annuus L.; SFK). Weanling female rats were fed diets containing 20% SFK in a 2x2x2 factorial design with marginal and adequate amounts of Ca, Zn, and Fe. Marginal Zn (11 mg/kg) and Fe (13 mg/kg), and Cd (0.18 mg/kg) were derived solely from 20% SFK. These amounts of Fe and Zn represented 39 and 90% of the NRC requirement for the rat, respectively. The marginal dietary Ca concentration (2.5 g/kg) was one-half the NRC requirement. After 5 weeks on the experiment, rats were fed 1 g of their respective diets containing SFK extrinsically labeled with 37 kBq 109Cd, and absorption was determined by whole-body counting techniques. Rats were then killed and organs collected for 109Cd assays. No effect of treatment on weight gain was observed; however, when dietary Zn was low, feeding marginal Ca elevated Cd absorption by 50% (P<0.05) over those fed adequate Ca and Zn. Feeding marginal Fe elevated Cd absorption >2.5-fold (P<0.001) over those fed adequate Fe. In contrast, the naturally occurring Zn in SFK that provided 90% of the rat's requirement was enough to deter excessive absorption of Cd and enough to alone prevent significant elevation of organ Cd. Organ content of 109Cd and Cd followed the same general pattern as whole-body absorption. These data show that marginal nutritional deficiencies of Ca and Fe can readily enhance the body burden of Cd that comes from the diet. Also, some natural competitors of Cd, such as Zn, contained in foods can independently minimize Cd absorption.