Science  /  Explainer

How the Arrival of Iodized Salt 100 Years Ago Changed America

On May 1, 1924, the first iodized salt appeared on shelves, quickly solving an iodine deficiency crisis that plagued the northern U.S. “goiter belt.”

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.