Oral calcium supplements to reduce the bioaccessibility and bioavailability of arsenic and lead in contaminated soil

While increasing dietary calcium (Ca) intake can reduce the oral bioavailability of heavy metal(loid)s, it remains unclear whether a series of Ca compounds can simultaneously reduce the oral bioavailability of As and Pb from soil. The influence of eight Ca compounds on As and Pb bioaccessibility in soils was determined using an in vitro gastrointestinal model, following which an in vivo bioassay was used to determine the most effective Ca compounds on As and Pb bioavailability. The results showed that, while CaHPO₄ was the most effective in reducing Pb bioaccessibility in gastric (from 19.0 to 92.3% to 14.3‒66.4%) and intestinal (from 0.18 to 17.5% to 0.00‒3.53%) phases, it conversely exhibited the strongest capacity to enhance As bioaccessibility. However, the addition of Ca acetate reduced the Pb bioaccessibility in the gastric phase and As bioaccessibility in the intestinal phase. More importantly, the Ca acetate (~ 200 mg Ca kg^-1) was the most effective in reducing relative bioavailability of As and Pb based on mouse bioassay. Our finding verify the efficacy of Ca acetate in mitigating the oral bioavailability of As and Pb. This study lays a theoretical foundation for the targeted use of optimal Ca compounds to mitigate human exposure risks to environmental As and Pb.