Meta-analysis of Feeding Trials Investigating Cadmium Accumulation in the Liver and Kidney of Sheep

Human cadmium intake derives mainly from food sources, and cadmium can be present in high concentrations in some offal. A meta-analysis using random effects modeling was carried out to integrate the results of 21 controlled randomized trials in which sheep were fed diets with elevated cadmium levels and cadmium concentrations in their livers and kidneys were recorded after slaughter. Resulting predictions of cadmium accumulation in sheep are applicable to a broad set of exposure situations allowing the critical examination of cadmium in the human food chain. The product of the cadmium concentration in the feed and the duration of exposure to that feed were significant predictors of the cadmium concentration in livers and kidneys. The predominantly organic rather than inorganic form of cadmium in the feed further increased accumulation. Other variables (dry matter intake, the vehicle of the elevated cadmium in the diet, animal age, weight, and sex) were not significant. As a result, the prime measure to decrease the risk of cadmium from animal origin adversely affecting human health should be restricting the animals’ cumulative cadmium intake. It is suggested that this might be achieved by preventing the livers and kidneys of older animals from entering the human food chain.