<i>In Vivo</i> Bioavailability and <i>In Vitro</i> 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 <i>in vivo</i> mouse model and compared it with I bioaccessibility measured by three <i>in vitro</i> 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 (<i>r</i> = 0.50, <i>p</i> < 0.01) and total dietary fiber contents (<i>r</i> = -0.28, <i>p</i> < 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 <i>in vitro</i> extraction. Correlation analysis demonstrated that PBET was the best predictor for I RBA (<i>R</i>² = 0.64). These results developed an appropriate <i>in vitro</i> method for predicting I bioavailability in seaweeds, which is highly beneficial for the accurate assessment for I dietary intake.