In Vivo Bioavailability and In Vitro Bioaccessibility of Iodine in Edible Seaweeds: Method Development and Health Implications

Both iodine (I) deficiency and I excess can adversely affect human health. Seaweed consumption is one of the most important natural sources for I. This study assessed I relative bioavailability (RBA) in seaweed using an in vivo mouse model and compared it with I bioaccessibility measured by three in vitro methods (Physiologically Based Extraction Test (PBET), the Solubility Bioaccessibility Research Consortium (SBRC), and the Unified Bioaccessibility Research Group of Europe Method (UBM)). Total I concentrations in 26 seaweed samples from four species ranged from 52.4 to 1322 mg/kg of dry weight. The I RBA varied from 18.5% to 89.0%, significantly influenced by inorganic I percentage (r = 0.50, p < 0.01) and total dietary fiber contents (r = −0.28, p < 0.05) in seaweeds. The I bioaccessibility varied among species and methods and were affected by the pH of gastric solution, as well as the structural changes in seaweed during in vitro extraction. Correlation analysis demonstrated that PBET was the best predictor for I RBA (R² = 0.64). These results developed an appropriate in vitro method for predicting I bioavailability in seaweeds, which is highly beneficial for the accurate assessment for I dietary intake.