Iodine content in water and food is dependent upon the iodine content of the soil. In many countries, iodine has been added to table salt, at a 1 per 10,000 ratio with salt. In ancient times, goiter was treated by burnt sponge or seaweed, both rich in iodine. Children with debility or those who revealed slow development, failure to gain weight or retard growth showed subsequent steady improvement. Cretinism - a child is physically dwarfed, retarded, and has an enlarged abdomen.
Iodine supplements can reverse some of the affects.
Goiter - The thyroid gland enlarges and causes a swelling in the throat. It usually occurs where soil has been leached of iodine, usually tropical rains, glacial soils, or areas with very little soil iodine. It is a painless condition but continued growth can block the throat and require surgery. Iodine content in plants varies according to soil content, time of year and species of plant. Iodine content of plants is at a maximum in autumn and winter.