Variations in cadmium and lead bioaccessibility and human health risk assessment from ingestion of leafy vegetables: Focus on the involvement of gut microbiota

Abstract

Research on the influence of gut microbiota on cadmium (Cd) and lead (Pb) bioaccessibility in leafy vegetables and the associated health risk is limited. This study applied in vitro-simulated digestion coupled with a human colon microbiota culture model to determine the bioaccessibility of Cd and Pb in leafy vegetables across different digestion phases. Compared with those of the gastric phase, the bioaccessibility values for the small intestinal phase varied, either decreased by 1.2–2.8-fold for Cd or increased by 1.0–3.6-fold for Pb. Notably, substantial reductions in the bioaccessibility of Cd and Pb were observed during colon incubation with gut microbiota, likely due to the immobilization of these elements by gut microbiota through adsorption, complexation and precipitation. Furthermore, the health risk assessment (HRA) showed that estimating the health risk of Cd and Pb based solely on their total concentrations in leafy vegetables could lead to overestimation. In contrast, a bioaccessibility-corrected HRA, which incorporates the bioaccessibility of Cd and Pb after ingestion, provided a more accurate risk assessment for leafy vegetable consumption. Importantly, the bioaccessibility-corrected HRA for both the small intestinal and colon phases indicated no apparent health risk for either adults or children. Collectively, these findings highlight the crucial role of gut microbiota in modulating Cd and Pb bioaccessibility after oral exposure, potentially mitigating the associated health risk. Therefore, targeted interventions aimed at modulating gut microbiota may serve as a potential strategy to alleviate the health risk posed by metal-induced toxicity from Cd and Pb in humans.