Arsenic bioaccessibility in rice grains via modified physiologically-based extraction test (MPBET): Correlation with mineral elements and comparison with As relative bioavailability.

Rice consumption is a major dietary source of human exposure to arsenic (As), with As bioavailability being an important factor influencing its health risk. In this study, the As bioaccessibility was measured in 11 rice grains (140-335 μg As kg), which were compared to As relative bioavailability previously measured based on a mouse bioassay (Li et al., 2017). Using modified physiologically-based extraction test for rice (MPBET), As bioaccessibility in raw rice samples (44-88% in the gastric phase and 47-102% in the intestinal phase) was similar to those in cooked rice (42-73% and 43-99%). Arsenic bioaccessibility in rice was generally higher in the intestinal phase than in the gastric phase, with Fe and Ca concentrations in rice being negatively correlated with As bioaccessibility in the gastric phase (R = 0.47-0.49). In addition, for cooked rice, strong positive correlation was observed between bioaccessible As and inorganic As (R = 0.63-0.72), suggesting inorganic As in rice was easier to dissolve than organic As in gastrointestinal digestive fluids. Due to limited variation in As bioaccessibility and As bioavailability among the 11 samples, a weak correlation was observed between them (R = 0.01-0.03); however, As bioaccessibility values measured by the gastric phase (GP) of the MPBET agreed with As bioavailability values based on a mouse bioassay, suggesting the potential of the MPBET to predict As bioavailability in rice. Future work is needed to ascertain the robustness of the MPBET in predicting As bioavailability in rice using additional samples.