Mercury and selenium in fish and shellfish: Occurrence, bioaccessibility and uptake by Caco-2 cells

This study evaluates Hg and Se concentrations and bioaccessibility (element solubilised after simulated gastrointestinal digestion) in 16 raw seafood species consumed in Spain. The concentrations varied greatly (Hg, 3.8–1621 ng/g wet weight, ww; Se, 84–1817 ng/g ww). Only one sample of swordfish exceeded the Hg limit permitted in Spain (1 mg/kg), and for this sample the Hg/Se molar ratio and Se Health Benefit Value food safety criteria also indicated the presence of a risk. Bioaccessibility of Hg (35–106%) and Se (17–125%) was very variable and the Hg/Se molar ratio in the bioaccessible fraction was less than one for all samples. Transport by Caco-2 cells, an intestinal epithelium model, was also evaluated from the swordfish bioaccessible fraction. Hg and Se transport from the food was less than 14%, and cell retention was much greater for Hg (49–69%) than Se (8–12%).