Iodized salt was first introduced in the United States in the area surrounding the
Great Lakes in 1924 in an attempt to increase iodine intake to reduce incidences of
goiter . Within 25 years, goiter was virtually eliminated in that region. In subsequent years, research has also shown that use of iodized salt also reduces the rates of
mental retardation and
cretinism.
The potential toxicity to the thyroid of excess iodine in the diet was the chief objection raised against iodized salt when the concept was initially proposed. Subsequent studies showed this not to be a serious problem. One quarter teaspoon of iodized salt will provide about 95 micrograms of iodine; the recommended daily intake (RDI) for adults is 150 micrograms. The maxiumum daily intake level (UL) is 1100 micrograms, which you'd get after consuming the salt involved in about 70 tequila shooters (after which your thyroid would be the least of your concerns).
Iodine deficiency is still a major problem in many third world countries, according to the WHO and UNICEF. This is doubly tragic because the salt iodization process is now both inexpensive and relatively simple. Organizations such as Kiwanis International are sponsoring efforts to combat iodine deficiency disorders (IDDs), and some governments are moving to increase availability of iodized salt amongst the population.
Countries such as India have attempted to ban non-iodized salt in an attempt to prevent IDD, but have faced stiff opposition from traditional salt producers.
In the US, salt that has been iodized with either cuprous iodide or potassium iodide and is destined for "human food use" must be labeled with the statement "This salt supplies
iodide, a necessary nutrient." Salt that has not been iodized must be labeled "This salt does not supply iodide,
a necessary nutrient." The truly paranoid may wish to subject their salt to a starch test to verify that it is, in fact, full of iodized goodness.
Sources:
- FDA 21CFR100.155
- http://www.saltinstitute.org/
- Medline Plus