Iodine is an essential element in healthy human life enabling the function of our thyroid gland, “the master gland of metabolism.” Too little iodine can produce a thyroid enlargement known as a goiter; more significantly, iodine deficiency impairs fetal brain development and imposes on a newborn infant a lifetime intellectual deficit of 10 – 15 IQ points. Too much iodine is also a problem, though less common.
We ingest iodine with our foods. When we eat seafood, plants grown where soil contains iodine and the meat of animals whose forage grows in such soils, our bodies usually take in enough iodine. But glacial action and natural weathering can leach iodine from the soil leaving it deficient. Plants and animals raised in areas with iodine-deficient soil will be poor sources of iodine in the human diet and the animals themselves will be less healthy and productive.
Scientists identified iodine as an element in the early 19th century and only 20 years later, French scientist J-B. Boussingault reported his conclusion that iodized salt would be an effective prophylaxis for goiter, stating "I am convinced that goitre would disappear...if the authorities made available in every district town...a depot of salt containing iodine." Yet it took another century for "authorities in the U.S. and Switzerland to effectuate Boussingault's insight.
David Marine (1880-1976) is the "father" of iodized salt in the United States. As the result of research on endemic goiter and iodine deficiency by Marine and co-workers research, the Michigan State Medical Society, in 1924, launched a goiter prevention program using iodized salt, making iodized salt the first of what we now term “functional foods.”
Medical science since has identified a far more serious threat than the cosmetic problem of goiter -- mental retardation. In October 2007, the American Thyroid Association hosted a symposium with valuable current information and capturing the excitement of the progress; it was entitled "A public health triumph in the making." UNICEF Deputy Executive Director Kul Gautam delivered a stirring charge to delegates that captured not only the moral imperative of universal salt iodization, but included an outstanding historical review of the entire issue. Gautam told delegates:
"IDD is the single greatest cause of preventable mental retardation. Severe deficiencies cause cretinism, stillbirth and miscarriage. But even mild deficiency can significantly affect the learning ability of populations. Scientific evidence shows alarming effects of IDD. Even a moderate deficiency, especially in pregnant women and infants, lowers their intelligence by 10 to 15 IQ points, with incalculable damage to social and economic development of nations and communities. Today over 1 billion people in the world suffer from iodine deficiency, and 38 million babies born every year are not protected from brain damage due to IDD. These 38 millions, or nearly 30 percent of the world’s newborns, come from families that are the least educated, most isolated and economically disadvantaged. The mark of a civilized society is how well it takes care of its most vulnerable and deprived communities. If we continue to fail to reach these newborns, we will be consigning them to an inter-generational cycle of poverty and injustice."
In the United States, salt producers cooperated with public health authorities and made both iodized and plain salt available to consumers at the same cost. Newspapers urged people to use iodized salt for the prevention of iodine deficiency. The Michigan program was highly successful and iodized salt use quickly spread throughout the country. Ultimately, household use of iodized salt eliminated iodine deficiency in the North America. In 1955, researchers reported that 75.8% of U.S. households used only iodized salt. The Salt Institute estimates that nearly 70% of the table salt sold in the United States is iodized. Virtually none of the salt used in processed foods is iodized, however, so the transformation of eating practices in the U.S. and many other countries, substituting meals prepared outside the homes using plain salt for home-cooked foods containing iodized salt, has led to an erosion of iodine in the U.S. diet. Canada, Australia/New Zealand and much of western Europe long ago addressed the need to ensure availability of iodized salt.
Around the world, however, iodine deficiency remains a major health problem. The Salt Institute has been deeply involved in the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) and, after the salt industry’s Salt2000 Eighth International Symposium on Salt, helped found and continues to provide leadership to The Network for the Sustained Elimination of Iodine Deficiency. Other Network members include ICCIDD, UNICEF, the World Health Organization, Kiwanis International and the Centers for disease control as well as the global salt industry. These groups and national counterparts have made remarkable progress, but even today fully 30% of the households around the world lack access to iodized salt despite the strong, vocal consensus and extremely modest cost.
Salt is hygroscopic; it attracts moisture. Fine grained salt, like table salt, popcorn salt, etc. would fuse together in highly humid conditions, so salt producers in modern salt refineries add any of a number of free-flowing agents to salt. All are, of course, approved food additives by national food safety regulatory agencies (e.g. FDA, in the US). FDA, for example, has approved 18 different additives for salt .