Before iodized salt was developed, some people experienced a number of developmental difficulties, including problems with thyroid gland function and mental retardation. In the 1920s, we learned that these conditions could usually be treated easily with the addition of iodide anion to the diet. One easy way to increase iodide intake was to add the anion to table salt. This simple step greatly enhanced health and development. Large amounts of iodide ion are also found in seaweed such as kelp (see picture above) and saltwater fish.
Context: People in the coastal area naturally get more iodide from food items because the soil has more iodized salt. But farther we go inland, the soil lacks necessary iodine. As a result, inland population do not get enough iodine naturally.
Question: Would people in coastal area risk tyroid gland problems less or more than the inland people if they only use home grown foods?