Getting enough iodine in our diets isn’t something that most of us think about. Thanks to a simple yet miraculous public health innovation a century ago, the often devastating symptoms of iodine deficiency have become a thing of the past—in the United States, at least.
Just over 100 years ago, iodine deficiency was such a significant problem in many northern U.S. states that the region became known as the “goiter belt.” Though uncommon today, goiters (visibly swollen thyroid glands that appeared as huge bulges in the neck) were a telltale sign of iodine deficiency. A less visible yet far more tragic symptom was the prevalence of permanent neurological impairments and low IQs among children whose mothers had lacked iodine in their diets during pregnancy and lactation.
With very limited supplies of iodine in the soil and water from the Great Lakes, Michigan was one of the worst-affected states. During World War I, the scale of the problem became impossible to ignore. In one Michigan county, more than 30% of young men registered for the wartime draft were observed to have goiters, which tended to disqualify them from military service. Shortly after, a general population survey found that some Michigan locales had an even higher incidence of goiters.
In 1922, Dr. David M. Cowie, a University of Michigan professor of pediatrics, recommended adding iodine to table salt to supply the mineral to the entire population. He had become acquainted with this practice while studying in Germany and was convinced that it would benefit Michigan's iodine-deficient residents. A 1917-1919 study of Ohio schoolgirls further underlined the importance of iodine supplements, which significantly reduced the rate of goiters among them.
Rather than mandating the iodization of all salt, Cowie and his colleagues at the Michigan State Medical Society launched a successful public health education initiative about the importance of iodine. The Michigan Salt Producers Association was easily brought on board, given that adding iodine to salt was likely to increase their profits along with serving the public good. By May 1924, Michigan grocery stores were selling table salt containing .01% sodium iodide, a clinically significant amount that did not affect the product’s color or taste. By the fall of that year, iodized salt had become commercially available in many other states, with overwhelmingly positive results. It soon became the norm throughout the country, and the incidence of goiters and other iodine deficiency symptoms fell dramatically.
A public health victory, but not for all:
- In 1935, a survey found that the incidence of goiters in Michigan had decreased by up to 90% in many parts of the state.
- The efforts of Dr. Cowie and the Iodized Salt Committee were such a success that today, surprisingly few people, even in Michigan, are aware of this widespread health issue that plagued earlier generations.
- Tragically, iodine deficiency is still a problem in many parts of the world, despite the affordability of the solution. It costs just a few pennies a year to provide an individual’s recommended amount of dietary iodine. However, iodine deficiency is estimated to affect around 50 million people worldwide and is the leading cause of preventable intellectual impairment.
