Accumulation of Dietary Cadmium (Cd) in Rabbit Tissues and Excretions: A Comparison of Lettuce Amended with Soluble Cd Salt and Lettuce with Plant-Incorporated Cd

Abstract

Quantifying the transfer of Cd from foods to mammalian target organs is key to estimating the health risk from this exposure; however, the bioaccumulation of Cd from foods is modified by many dietary components. Studies of dietary Cd absorption would be simpler if it were known that Cd added to foods as a soluble salt was as bioavailable as Cd incorporated during growth of the food species. Rabbits were fed, for 16 d, fresh lettuce containing cadmium incorporated into the lettuce during growth or added to the lettuce before feeding, or lettuce with no Cd but soluble Cd administered to the animals by gavage. There was a marked positive relationship between increased Cd dose and its accumulation in kidney; the slopes for the gavage and added treatments were not clearly different from the incorporated treatment; liver data were highly variable. In a 10-wk study of Cd-incorporated and -amended lettuce diets, for the incorporated and control diets there was less Cd accumulation in the kidneys, but not liver, per unit cumulative dose, than for the amended diet. Cd accumulation in the small intestine and Cd concentration in feces, both per unit daily dose, were smaller for the incorporated than for the control and amended diets; Cd concentrations in bile, urine, and serum, per unit daily dose, were higher in the control diet than values in the amended diet, which were higher than the incorporated diet. These differences could not be accounted for by variation in Fe or Zn contents of the diets. Thus, data suggest that Cd-amended diets overestimate bioaccumulation in kidney, an important target organ, by up to one-third, and that studies of short duration are not adequate to evaluate Cd bioavailability from food.

The authors acknowledge the support of the Canadian Network of Toxicology Centres (CNTC) as well as the Collaborative Health Research Projects (CHRP) program of the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canadian Institutes of Health Research (CIHR).