Bioaccessibility and risk assessment of Pb, Se, Cd and Zn from seaweed

Plant-based protein sources such as seaweed can contain trace elements (TEs) having nutritional value like Zn and Se, and toxic ones like Pb and Cd. For the first time, the bioaccessible fractions of these TEs in artificial saliva, gastric juice and intestinal fluid were determined in edible seaweed certified reference material GSEA-1, using a continuous on-line leaching method (COLM) coupled to inductively coupled plasma mass spectrometry. Bioaccessible concentrations from the COLM and a conventional batch method were the same according to a Student’s t test at the 95% confidence level, except for Cd, which exhibited a significantly lower bioaccessibility with the COLM. With both methods, less than 25% of total Pb, Zn, Cd and Se was bioaccessible. The COLM released Cd, Pb and Zn from seaweed in each of the three gastrointestinal phases, unlike the batch method. Based on risk calculations incorporating the highest measured bioaccessibility between the batch method and the COLM to assess the worst-case scenario, the hazard quotients (HQs) for Zn and Se were below 0.2, indicating negligible risk, while Pb and Cd HQs exceeded 1 in some cases, indicating that some moderation may be prudent when consuming protein shakes prepared with seaweed powder as protein supplement. • The bioaccessibility of Zn, Se, Cd and Pb was measured in seaweed reference material • A continuous online leaching method and a batch method mostly gave similar results • The bioaccessible and certified concentrations were used in a human risk assessment • Zn and Se pose negligible to minimal health risk and are beneficial nutrients • Pb and Cd present a minimal to elevated health risk upon daily seaweed consumption