How the arrival of iodized salt 100 years ago changed America
In the early 20th century, iodine deficiency was ravaging much of the northern United States. The region was widely known as the “goiter belt,” for the goiters - heavily swollen thyroid glands - that bulged from many residents’ necks.
The issue was more than cosmetic: Iodine deficiency during pregnancy and lactation often led to children with severely diminished IQ and other permanent neurological impairments.
And Michigan was at the epicenter of the crisis.
The soil there didn’t have much iodine. Nor did the freshwater Great Lakes. And so the inhabitants didn’t have much iodine, either.
The prevalence of iodine deficiency in the state became strikingly apparent after the outbreak of World War I. Simon Levin, the medical examiner for the draft board in Michigan’s Houghton County, observed that more than 30 percent of registrants had a demonstrably enlarged thyroid, which could disqualify them from military service. In fact, it was the leading cause of medical disqualification in northern Michigan.
Levin’s observations prompted a survey of the general population in several Michigan counties, which revealed that some parts of Michigan had an even higher rate of goiters than the heavily afflicted group of young men from Houghton County.
Meanwhile, a study in Ohio conducted from 1917 to 1919 found that schoolgirls provided with iodine supplements saw a hugely reduced rate of goiters compared with girls who did not receive the supplements.
These developments came to the attention of David M. Cowie, the first professor of pediatrics at the University of Michigan. Having studied in Germany, he was familiar with the Swiss practice of adding iodine to table salt.
At a 1922 symposium held by the Michigan State Medical Society, Cowie recommended the iodization of salt, a near-ubiquitous food product that would quickly reach a large percentage of the population.
Cowie and members of the new Iodized Salt Committee initially sought to propose a bill to the state legislature mandating that Michigan iodize all salt for human consumption. But a lawyer told Cowie that people might object to a state requirement that they consume a particular food product. The more effective option, he was persuaded, was to convince the public that iodized salt was in its best interest.
So the Michigan State Medical Society launched an initiative to educate locals on the need for iodine. Cowie, along with colleagues from the University of Michigan and state health department workers, began delivering iodine lectures across the state. Many thousands of receptive listeners came, at a time when the American public was beginning to show an interest in vitamins, minerals and other aspects of nutrition.
Cowie also presented the case for iodization to the Michigan Salt Producers Association. The salt producers, seeing the potential for profits from the new product - and perhaps wanting to do a public service - were easy converts. They agreed to iodize salt for animal consumption as well, as many Michigan farm animals were contending with their own goiters.
On March 15, 1924, the Michigan State Medical Society voted to recommend the use of salt containing .01 percent sodium iodide. This amount of iodine did not change the salt’s color and had virtually no effect on its taste.
The first commercially available iodized salt in the United States appeared in Michigan grocery stores on May 1, 1924. Other states took notice; the potential benefits were obvious. By the fall of 1924, iodized salt was being distributed across the nation.
Customers still had a choice to buy iodized or noniodized salt, but increasingly they were going for the iodine. Within a decade, iodized salt accounted for 90 to 95 percent of Michigan’s salt sales. And the results were undeniable: A 1935 survey found that incidence of enlarged thyroids had decreased in the state by as much as 90 percent.
Not long after Michigan’s success at kick-starting salt iodization in the United States, iodine-fortified salt became a daily part of the American diet. This slight but crucial modification eventually saw goiters become rare to the point of near extinction, erasing the “goiter belt” forever.
Other major 20th-century U.S. public health campaigns, such as antismoking and occupational safety, remain relevant to the present day. The American goiter, though, either goes ignored or exists merely as a historical curiosity.
“The very success of the campaign, all but eliminating goiters, has made the issue fall out of public consciousness,” said Jim Tobin, a Michigan native and professor of journalism at Miami University of Ohio. Cowie is largely unknown even within Michigan, noted Tobin, who wasn’t aware of the history behind iodized salt until he wrote an article about Cowie.
While it’s been largely eliminated in the United States, iodine deficiency remains a significant problem in other parts of the world. About 50 million people show clinical symptoms of the condition. At the start of the 21st century, iodine deficiency was still the world’s leading cause of preventable intellectual impairment.
This fact is especially unfortunate given the low price of the remedy. The cost of iodizing salt amounts to just several cents a year per person. The cost of not iodizing salt continues to speak for itself.
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