Clinical Trial Summary
Iodine is an essential micronutrient for the production of thyroid hormones and its
deficiecny remains a global problem impairing health. The primary source of iodine is the
diet via consumption of foods, including cooked foods with iodized salt, dairy products, or
naturally abundant seafood. Currently, the recommendation of dietary iodine intake is 150 μg
per day in adults who are not pregnant or lactating. The ingestion of iodine or exposure
above this threshold is well-tolerated and nearly no health problems are observed. The diets
processed and cooked with iodized salt are generally important iodine sources, however, high
iodine intake is a result of routine consumption of several kinds of edible algae in coastal
regions, with varying contributions depending on the amount of seafood consumed.
Iodine absorption mainly depends on the iodine species in foods and possibly on the iodine
status of the individual. Further, there was little available data on iodine absorption or
bioavailability from different dietary sources, such as natutal kelp and fortified food with
potassium iodide. To our knowledge, inorganic iodide is thought to be absorbed almost
completely (over 90%). However, only about two-thirds of some forms of organically-bound
iodine are absorbed. The different sources of iodine absorption have not been accurately
quantified and compared in humans. Therefore, the purposes of this study were to quantify the
iodine absorption of natural kelp in male and female adults and compare with the
bioavailability from an iodine water solution (potassium iodide). This stduy will obtain the
actual iodine bioavailability and the difference for different source of foods.
This study is a randomized, cross-over design and aims to evaluate the iodine bioavailability
(measured using excretion in urine and fece) from different source and administered dose of
iodine, such as natural kelp and potassium iodide delivering a dialy iodine intake about 600
µg and 1200 µg. This study will compare and measure to the ingestion of natural kelp and
potassium iodide within one subject by three stages: (1) normal iodine intake stage (iodine
intake >150 µg/day); (2) intervention stage, a bowl of soup with an extrinsic iodine dose of
about 600 µg; or a bowl of natural kelp with a certain iodine content of about 1200 µg
potassium iodide.