Different Cadmium Bioavailability from Wheat and Rice Dictates Toxicity via Distinct Intestinal Pathways in Mice

Cadmium (Cd)-contaminated rice and wheat cause significant harm to public health. However, mechanistic differences in Cd bioavailability and toxicity between the staple foods through intestinal transport and gut microbiota remain insufficient. In this study, Cd-containing whole wheat and polished rice were fed to mice, showing over 2-fold lower Cd accumulation in the liver and kidneys of wheat-fed mice compared to rice-fed mice. One contributor was higher iron, calcium, and zinc contents in wheat than in rice, leading to a lower expression of iron, calcium, and zinc transporters in the duodenum of wheat-fed mice. Additionally, fiber-rich wheat caused higher relative abundance of Lactobacillus reuteri, strengthening intestinal integrity and tight junction expression, promoting fecal Cd excretion, and upregulating bile acid metabolism in the gut. The transporter downregulation and gut health improvements collectively contributed to lower wheat-Cd bioavailability. Findings indicate that Cd-containing wheat may pose remarkably lower health risk to humans compared to rice.