Iodine is added to salt as a mineral supplement. This practice began in the early 20th century to prevent goiter, a swelling of the thyroid gland that occurs from a deficiency of iodine. Goiter was common in some areas of the United States where the soil was lacking in iodine, which meant that the diet of local populations was iodine-deficient.
Discovery of Iodine
The French chemist Barnard Courtois first extracted iodine from seaweed in 1811. Seaweed has been effective as a treatment for goiter since ancient times, but it was not until 1915 that iodine was isolated from proteins produced by the thyroid gland. David Marine and O.P. Kimball of Cleveland, Ohio, then proved that endemic goiter was caused by iodine deficiency. Subsequently, health officials realized that adding iodine to salt would be a convenient way of supplementing local diets with the mineral.
History Dietary Sources
Dr. David Murray Cowie of the University of Michigan and the Michigan State Medical Society persuaded Diamond Crystal Salt and Morton Salt to produce iodized salt. By the 1930s, more than 90 percent of the salt Americans consumed was iodized. The incidence of goiter fell dramatically in the United States, and many other countries subsequently began iodizing their salt. Iodine is mostly found in seafood, seaweed and ocean fish, all of which can accumulate the iodine present in sea water.
Dietary Iodine
Iodine also occurs in the soil of coastal areas. Examples of other foods that contain iodine include dairy foods, eggs and beans. The amount of iodine present in foods can vary quite a bit, however. Although people living in less-developed areas in the world may still require iodine supplementation in salt, this may no longer be necessary in the United States. Americans today eat a much more varied diet that includes foods from many areas, so you are much less likely to lack iodine in your diet.
Iodine Requirements
Your daily needs for iodine change from childhood to adulthood, increasing from about 90 mcg to150 mcg, Pregnant and lactating women need about 200 mcg. Your thyroid gland needs iodine to make thyroid hormones, which regulate your metabolism. Iodine deficiency leads to the underproduction of these hormones, various thyroid diseases and growth problems in children. The thyroid gland stores the hormones and releases them into the blood as necessary.
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