Iodized Salt
People started adding iodine to salt because in some parts of the world serious, chronic iodine deficiency was incredibly widespread, which was causing a range of health issues. But how was that solution arrived at?
Research:
- "Iodine." World of Chemistry, Gale, 2000. Gale In Context: Science, link.gale.com/apps/doc/CV2432500388/GPS?u=mlin_n_melpub&sid=bookmark-GPS&xid=42a73bea. Accessed 17 May 2024.
- "Iodine." World of Scientific Discovery, Gale, part of Cengage Group, 2007. Gale In Context: Science, link.gale.com/apps/doc/CV1648500324/GPS?u=mlin_n_melpub&sid=bookmark-GPS&xid=fabf4422. Accessed 17 May 2024.
- Bishai, David and Ritu Nalubola. “The History of Food Fortification in the United States: Its Relevance for Current Fortification Efforts in Developing Countries.” Economic Development and Cultural Change , Vol. 51, No. 1 (October 2002). https://www.jstor.org/stable/10.1086/345361
- Cameron, A.T. “Iodine Prophylaxis and Endemic Goitre.” Canadian Public Health Journal, Vol. 21, No. 11 (NOVEMBER, 1930). Via JSTOR. https://www.jstor.org/stable/41976052
- Cameron, A.T. “Iodine Prophylaxis and Endemic Goitre.” Canadian Public Health Journal, Vol. 21, No. 10 (OCTOBER, 1930). Via JSTOR. https://www.jstor.org/stable/41976030
- Cavanaugh, Ray. “How the arrival of iodized salt 100 years ago changed America.” Washington Post. 5/1/2024. https://www.washingtonpost.com/history/2024/05/01/iodized-salt-100-years-deficiency/
- Feyrer, James et al. “The Cognitive Effects of Micronutrient Deficiency.” Journal of the European Economic Association, April 2017. Via JSTOR. https://www.jstor.org/stable/10.2307/90023421
- Goodman, Johnah. “A National Evil: Jonah Goodman on the curse of the goitre in Switzerland.” London Review of Books. 11/30/2003. https://www.lrb.co.uk/the-paper/v45/n23/jonah-goodman/a-national-evil
- Kimball, O.P. “History of the Prevention of Endemic Goitre.” Bulletin of the World Health Organization. 1953.
- Kohn, Lawrence. “Goiter, Iodine and George W. Goler: The Rochester Experiment.” Bulletin of the History of Medicine, Vol. 49, No. 3 (FALL, 1975). Via JSTOR. https://www.jstor.org/stable/44450239
- Leung, Angela M et al. “History of U.S. iodine fortification and supplementation.” Nutrients vol. 4,11 1740-6. 13 Nov. 2012, doi:10.3390/nu4111740
- Markel, H. “’When it rains it pours’: endemic goiter, iodized salt, and David Murray Cowie, MD.” American journal of public health vol. 77,2 (1987): 219-29. doi:10.2105/ajph.77.2.219
- Markel, Howard. “A grain of salt.” The Milbank quarterly vol. 92,3 (2014): 407-12. doi:10.1111/1468-0009.12064
- McIntire, Tracey. “Gunpowder and Seaweed: The Story of Iodine.” National Museum of Civil War Medicine. 10/19/2022. https://www.civilwarmed.org/story-of-iodine/
- Newton, David E. "Iodine." Chemical Elements, edited by Kathleen J. Edgar, 2nd ed., UXL, 2010. Gale In Context: Science, link.gale.com/apps/doc/CV2640200041/GPS?u=mlin_n_melpub&sid=bookmark-GPS&xid=a54dec8e. Accessed 17 May 2024.
- Niazi, Asfandyar Khan et al. “Thyroidology over the ages.” Indian journal of endocrinology and metabolism vol. 15,Suppl 2 (2011): S121-6. doi:10.4103/2230-8210.83347
- Olsen, Robert. “Endemic Goiter in Switzerland: A Review of Recent Contributions to Its Etiology, Incidence, and Prevention.” Public Health Reports (1896-1970) , Jun. 9, 1933. Via JSTOR. https://www.jstor.org/stable/4580807
- Pearce, Elizabeth N. “Is Iodine Deficiency Reemerging in the United States?” AACE Clinical Case Reports. Volume 1, Issue 1, Winter 2015. https://www.sciencedirect.com/science/article/pii/S2376060520303680
- Stanbury, John, and John T. Dunn. "Iodine." Encyclopedia of Food and Culture, edited by Solomon H. Katz, vol. 2, Charles Scribner's Sons, 2003, pp. 281-283. Gale In Context: U.S. History, link.gale.com/apps/doc/CX3403400349/GPS?u=mlin_n_melpub&sid=bookmark-GPS&xid=12f688cc. Accessed 17 May 2024.
- Zimmermann, Michael B. and Maria Andersson, GLOBAL ENDOCRINOLOGY: Global perspectives in endocrinology: coverage of iodized salt programs and iodine status in 2020, European Journal of Endocrinology, Volume 185, Issue 1, Jul 2021, Pages R13–R21, https://doi.org/10.1530/EJE-21-0171
- Zoltan, Melanie Barton. "Salt." Food: In Context, edited by Brenda Wilmoth Lerner and K. Lee Lerner, vol. 2, Gale, 2011, pp. 699-702. In Context Series. Gale In Context: Global Issues, link.gale.com/apps/doc/CX1918600212/GPS?u=mlin_n_melpub&sid=bookmark-GPS&xid=21e3cd86. Accessed 17 May 2024.
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2024-06-05
37 min
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00:00:01 Speaker 1: Welcome to Stuff You Missed in History Class, a production of iHeartRadio. Hello, and welcome to the podcast. I'm Tracy V. Wilson and I'm Holly Frye. 00:00:16 Speaker 2: Back at the beginning of May, I read an article in the Washington Post called how the arrival of iodized salt one hundred years ago changed America. And I was immediately fascinated by this whole thing, And I also wanted to learn more than a thousand word newspaper article could tell me. I already knew, and I think maybe a lot of folks already knew from something like elementary school health class that iodine is added into table salt because our bodies need that iodine for thyroid reasons. And I also knew there are various people who, for whatever reason, don't like iodized salt or don't want to use it, and that was sort of the sum of my knowledge about the iodide salt. And so reading this Washington Post article, I didn't really grasp that adding the iodine to the salt was not just like a nutritional nice to have. They were not like well meaning public health people kind of like, wouldn't it be great if everybody just had enough iodine, just because it was to try to deal with a problem that in some parts of the world was really serious with chronic iodine deficiency. It was incredibly widespread in some places, and that was causing a range of actual health issues, not just wouldn't it be great if we all got enough iodine. 00:01:38 Speaker 1: So a complete history of salt would be its own episode, or perhaps even more than one. You could even have the story of salt as an entire podcast. I imagine. Of course, edible salt or sodium chloride makes food more flavorful, and it's an electrolyte that our bodies need to function correctly. Salt can also be used to preserve food through salting, curing, brining, or pickling, and there are lots of non dietary uses for it as well. So for those and other reasons, people have wanted and needed salt, going all the way back to our earliest beginnings, cultures all around the world have boiled or evaporated salt from water, including seawater and water from salt lakes or mineral springs. Animals besides us, need salt to often they get it from licking at salt deposits. So people who are living farther inland could sometimes find sources of salt by just watching what the animals were doing, even if salt had no other uses. Its importance in flavoring and preserving food has made it highly sought after all over the world for basically all of history. Some of the world's earliest trade networks were, of course, salt roads, and many of the earliest governments, established thousands of years ago, regulated the salt trade and establish salt stockpiles. Iodine is not nearly as abundant assault, but it is similarly critical. People and all other vertebrate animals need iodine for our bodies to function properly. Specifically, the body uses iodine to make thyroid hormones, and thyroid hormones regulate a number of body functions, including growth and metabolism, affecting virtually every cell in the body. The iodine we consume moves from the digestive system to the blood and from there to the thyroid gland, which produces those hormones. 00:03:35 Speaker 2: People only need a little bit of iodine. In the United States, the recommended daily allowance is only one hundred and fifty micrograms a day for adults. It's roughly half that For babies and children, the recommended daily allowance increases to two hundred and twenty micrograms during pregnancy and two hundred and ninety micrograms while lactating. But whether people can get that much eye iodine without access to fortified foods like iodized salt varies widely depending on where they live. There's iodine in seawater, and it's in the Earth's crust, but exactly how much iodine there is in a particular location depends on things like how close it is to the sea and geological changes that have taken place over thousands and thousands of years. 00:04:25 Speaker 1: The presence of iodine in seawater means that various types of seaweed and marine animals are also high in iodine, so people living in an island nation like Japan, where the traditional diet includes a lot of seafood and seaweed may be able to get enough iodine through their regular diet without some kind of supplementation. 00:04:46 Speaker 2: Generally speaking, things get trickier farther inland. How much iodine is available to people and animals depends on how much of it is present in the soil, so, for example, cows grazing on a pasture near the sea, where the iodine in the soil is replenished by the spray blowing in from the ocean, they might get enough iodine, and that means there would also be iodine in their milk. But high altitudes places where there are recurring floods or cycles of glaciers melting and refreezing, those places typically have very little iodine in the soil, so without some kind of supplementation, people and animals living there cannot get enough iodine in their diets. 00:05:28 Speaker 1: This isn't only a problem for humans who rely on these animals for food. Iodine deficiency in livestock is connected to things like still births, the deaths of young, and lower production of eggs and milk. As a side note, in today's world, some of the iodine and milk doesn't actually come from what the cows are eating. It's from the use of iodine as an antiseptic or sterilizer, both on the cow's utters and on equipment that's used in the dairy industry. 00:05:56 Speaker 2: There are also some things that can interfere with the bodies of bil to absorb iodine, including compounds found in cassava and millet, and some chemical pollutants. So a person living in an area where the soil is low in iodine, or whose diet includes a lot of those foods somebody who's exposed to these kinds of pollutants. These people could have even more difficulty getting enough iodine In people. 00:06:23 Speaker 1: Iodine deficiency can lead to a number of health issues. As we said earlier, the body needs iodine to make thyroid hormones. If the thyroid gland isn't getting enough iodine to do this, it enlarges as it tries to filter more iodine from the blood. This enlarged thyroid gland is called a goiter, and a goiter can put pressure on the blood vessels in the neck and on the trachea. There are other things that can cause goiter, including autoimmune disorders like graves disease, thyroid nodules, and cancers, but iodine deficiency is the most common cause of goiter worldwide, and yes, non human and animals can also develop goiter. 00:07:02 Speaker 3: Without enough iodine. 00:07:04 Speaker 2: The body also can't make enough thyroid hormone that leads to hypothyroidism. Symptoms and effects of hypothyroidism include things like fatigue, listlessness, difficulty concentrating, dry skin, feeling cold all the time, depression, irregular menstrual periods, among other things. Iodine and thyroid hormones also play an important role in brain development in utero. Iodine deficiency during pregnancy can lead to babies being born with congenital iodine deficiency syndrome, which a startling number of sources are still right now in the year twenty twenty four while we record this describing using the word cretinism, even though at this point that term has deeply insulting connotations. Congenital iodine deficiency syndrome can lead to developmental disabilities, deafness and inability to speak, and muscular skeletal issues. Treatment with iodine can resolve many of the issues associated with hypothyroidism, including the physical changes in babies born with congenital iodine deficiency syndrome, but not the damage to the brain that takes place during fetal development. Iodine wasn't discovered until the nineteenth century, but people in various parts of the world connected foods that are high in iodine with the prevention and treatment of goiter thousands of years ago. Documents from China dating back to about thirty six hundred BCE describe a reduction in goiter after eating seaweed or burned sea sponge. Seaweed and sea sponge continued to show up in medical texts in Asia, Europe, and Northern Africa afterward. Ierveateic texts from the Indian subcontinent dating back to about fourteen hundred BCE also include descriptions of hyperthyroidism and hypothyroidism, with treatments for hypothyroidism including things like milk, various grains, and bladder rack, which is a type of seaweed. Overall, earlier medical writers didn't know exactly what caused goiter. For example, those same Aervedic texts conclude that goiter was caused by edema, and various physicians throughout history have blamed goiter on a range of illnesses, poisons, and even tumors. But there are also written records of people making a connection between goiter and the symptoms of hypothyroidism like fatigue and difficulty concentrating. In the tenth century, Arab historian and geographer Al mas Udi described Europeans as having quote large bodies, dull understanding, and heavy tongues, which is often interpreted as a reference to how many people had hypothyroidism. In the sixteenth century. Paracelsus also made a connection between parents with goiter and children born with developmental delays and disabilities. People started to get a clearer understanding of the relationship but between goiter, thyroid hormone, and iodine after iodine was discovered in the nineteenth century. We'll have more on that after a sponsor break. In eighteen eleven, French pharmacist and chemist Bernon Courtois was working with seaweed at his father's saltpeter factory. This process involved burning the seaweed to produce soda ash and then adding sulfuric acid to it. One day, by accident, he added too much sulfuric acid. In the words of Humphrey Davy, this produced quote a beautiful violet vapor. Courtois was not sure what this vapor was, but he called it by the Greek word iodes, meaning violet. He didn't have time to really experiment with this, so he gave a sample to Joseph Luis Gaerusac. 00:10:53 Speaker 3: We talked about. 00:10:54 Speaker 2: This in our recent episode on Humphrey Davy, Davy and Gaelusac each described iodine as an element in eighteen thirteen. They made those descriptions about a week apart, and then they had an argument about who should get the credit for it. 00:11:08 Speaker 1: Like so many other newly discovered substances, once it had been identified and isolated, iodine made its way into medicines meant to treat all kinds of things. Of course, it didn't have an effect on most of them, and this experimental iodine treatment also carried the risk of what came to be known as the yod Basidou phenomenon. Yaod is the German word for iodine, and Carl Adolf von Basidu was the nineteenth century German doctor who worked with it. He was reportedly the first person to describe thyrotoxicosis, which occurs when there is too much thyroid hormone circulating in a person's body. The yod bazidoo effect is thyrotoxicosis in response to treatment with iodine. 00:11:53 Speaker 2: As a note, sometimes the terms thyrotoxicosis and hyperthyroidism are used interchangeably, but they're there are some slight nuances between these two terms. Those nuances are a little outside the scope of a generalist history podcast. Both of them however, involve an excess of thyroid hormone, they can cause things like tremors, weight loss, and low blood sugar, as well as a rapid heartbeat, and in extreme cases, can be fatal. It did not take long for people to realize that iodine could have a beneficial effect on goiter, though. In eighteen twenty one, Swiss physician Jef Freancois Quande published a paper detailing how he had reduced the size of goiter's by administering iodine. But Quondai didn't have a perfect process. His iodine treatments led to hyperthyroidism in some of his patients, and this continued to be the case for other researchers through much of the nineteenth century. Around the same time, French agricultural chemist Jean Beausingaul was also suggesting that iodine might offer a treatment for goiter That was based on a correlation observed between the prevalence of goiter and how much iodine was in soil samples in the eighteen fifties. Another French researcher, Caspar Adolf Chattez, similarly described a relationship between how much iodine was in the air drinking water and soil in a particular area and the incidence of goiter there. In areas with more iodine, goiter was less common. He also published works suggesting that chronically low iodine levels could cause chronic goiter, but his conclusions really weren't widely accepted because people questioned whether the minute amounts of iodine that he was describing really could have such a pronounced impact on a person's body. In eighteen ninety five, German chemist Eugen Bauman pinpointed the presence of iodine in the thyroid glands and isolated a physiologically active substance from within the glands, but he didn't get far on figuring out exactly what the substance was or how it functioned within the body, and he died the following year at the age of forty nine. In the early twentieth century, David Marine published work demonstrating a clear connection between iodine levels and thyroid function, but at first this was not in humans. He was studying other animals, including farmed brook trout. These brook trout seemed to be prone to some kind of thyroid dysfunction. Before Marine carried out these experiments, the swellings and lesions on these trout's thyroid glands were believed to be a form of carcinoma. He concluded that in a lot of cases this was an ordinary goiter except in a fish, and that it could be resolved just by adding iodine to their water supply. Marine started publishing this work in nineteen oh seven, and within about a decade he was studying the connection between iodine and goiter in humans. He carried out the first controlled human experiment to t this in Akron, Ohio. The test subjects included more than four thousand schoolgirls, with half of them receiving small doses of iodine and the other half not. Only five of the girls receiving iodine developed some kind of thyroid condition, but that number in the group who didn't receive iodine was four hundred and seventy five. His book on the subject, titled The Prevention of Simple Goiter in Man, was published in nineteen seventeen. The Akron experiment started in nineteen sixteen, and it ran in parallel to some work on goiter prevention that was going on in two places where goiter was highly prevalent was the country of Switzerland and the state of Michigan. Although these are on two different continents, both of them have very low levels of iodine in the soil. The work in Switzerland started just a bit earlier. In some areas of the country, goiter wasn't particularly prevalent, but according to a survey published by doctor Heinrich Bircher in eighteen eighty three, in one suburb of the capital city of Bern, ninety four percent of men had goiters. In the early twentieth century, as many as ten percent of babies born in Switzerland showed signs of congenital thyroid deficiency syndrome, and according to death certificates, goiter was the cause of death for more than fifteen hundred people there between nineteen eleven and nineteen twenty. Another four hundred sixty three people died of thyroid cancer during that period. Researchers had proposed various ideas to explain why so many people in Switzerland had goiter and why it was so much more prevalent in some places in Switzerland than in others. Some of these ideas involved eugenics and the idea that people who had goiter or the symptoms of hypothyroidism must have had bad breeding. Heinrich Hunziker proposed that Switzerland's rates of goiter were caused by a lack of iodie. 00:17:00 Speaker 3: In nineteen fourteen. 00:17:02 Speaker 2: There was again a lot of opposition to his ideas of iodine supplementation, due to fears that that supplementation might poison people. 00:17:10 Speaker 1: Even so, at least one person tried to test out Hunsicker's ideas. That was Auto Bayard, from the town of Valet. He mixed iodine into salt at five different concentrations and distributed it to five families who were living in a remote area where the train only ran in the warmer months. About seventy five percent of the children living in this area reportedly had in large thyroid glands. In addition to providing salt to these families, Bayard supplied salt for the village's animals and to the bakery. He delivered the salt before the train shut down for the winter of nineteen eighteen. 00:17:48 Speaker 2: When he returned there in the spring, he found that people's thyroid glands had dramatically improved, and nobody seemed to have been harmed by the iodine that had been added to the salt. Biard heard about the Akron experiment not long after this, and he repeated his experiment on a larger scale with the help of the Swiss Health Authority. Byard was invited to present his research to the Swiss Goiter Commission on January twenty first, nineteen twenty two. He and the Commission were not completely sure why adding iodine to the salt was so effective at treating goiter, but it definitely seemed to work, so the Commission wanted to try implementing it nationally. We mentioned up at the top of the show that governments around the world had regulated salt for centuries, and that was the case in Switzerland. Switzerland is more formally known as the Swiss Confederation. Today it comprises twenty six member states known as cantons. In the nineteeneens that number was slightly smaller, but each of these cantons had a monopoly on the sale of salt there going all the way back to the medieval period, so it wasn't possible for Switzerland and as a nation, to just mandate the sale or use of iodized salt across the whole country, or to make national changes to the salt supply. They had to advocate for doing this with each of the cantons individually. Hans Eggenberger, chief doctor in the town of Harrisau, became a vocal advocate for the use of iodized salt, spearheading efforts both within the government and as a public relations campaign. By June of nineteen twenty two, the Goiter Commission had recommended the use of iodized salt to all of the cantons, and the first deliveries of iodized salt took place at November. Michigan was facing really similar rates of goiter to Switzerland. In the early twentieth century, this part of the United States had been nicknamed the goiter Belt due to the prevalence of goiter and thyroid disease in Michigan and surrounding states. In nineteen eighteen, as Otto Bayard was working on his salt experiment, doctor Simon Levin was conducting physicals in Houghton County, Michigan. Levin reported that thirty percent of the men that he examined had an enlarged thyroid. It was estimated that more than twenty thousand men in northern Michigan alone were ineligible for military service because of their goiters and an enlarged thyroid. Gland was the most common reason for medical disqualification from military service in this part of the United States. Since the United States was involved in World War One, this was seen as an urgent issue. 00:20:33 Speaker 1: Health officials in Michigan expanded their focus beyond military physicals and conducted a follow up study in two towns in Houghton County for people aged one to sixty one. They found that more than sixty four percent of the people examined had some kind of goiter. Almost half of school children showed some evidence of thyroid dysfunction. 00:20:54 Speaker 2: Canadian American physician David Murray Cowie was the first professor of pediatrics at the Universe of Michigan. He had learned about the Swiss efforts to add iodine to salt, and he recommended a similar program to the Michigan State Medical Society. In nineteen twenty two, the Society established an advisory committee in its Pediatric section to focus on this project. This would lead to the first widespread use of a fortified food product in the United States. We're going to talk more about that after we paused for a sponsor break. There were a lot of reasons behind the decision to add iodine to salts. Rather than trying some other strategy to get iodine into people's diets. Various experiments involving iodine supplements in the late nineteenth and early twentieth century hadn't been really successful, Like there were iodine syrups that tasted disgusting so children didn't want to take them, or these were supplements that only needed to be administered every few months, so people would just forget about them. Meanwhile, salt was something that virtually everyone used in cooking, and its use didn't really vary much from season to season, unlike in earlier eras where the salt trade could involve long and arduous journeys, which I mean, I guess it still could in the early twentieth century, but most people had access to salt at a local store at a reasonable price, and unlike today, there wasn't a big public health focus on reducing salt intake due to sodium's connection to high blood pressure. Salt wasn't the only thing that people tried adding iodine to in the US, though. In Rochester, New York, there was a plan to add ionine to the drinking water that started on April twenty fourth, nineteen twenty three. This involved adding sodium iodide to the inflow of the city's reservoir in a project overseen by doctor George W. Goehler, who was Rochester's health officer. He had his own backstory that we not getting into, including apparently opposing pasteurization because he had seen such a reduction in milk boorn illnesses through his own inspection program. This effort to add iodine to the water was relatively effective, but it had some challenges like the amount of iodine that could be added to the reservoir was not enough to keep the average person's thyroid working well, at least not if they drank a typical amount of water, so people were advised to drink more tap water, as much as three times more than they were typically drinking. The level of iodine in the tap water also dropped really quickly after it was added to the reservoir. 00:23:42 Speaker 1: A lot of people also objected to the idea of something being added to their drinking water, including other water authorities. For example, a write up by the British Water Works Association set in part quote, it is contrary to ordinary medical teaching to force a whole population to drink doped water to the benefit of the minority. There were also several fires that appeared to be arson and threats that there would be more fires if this program was not stopped. Although the rate of goiter in and around Rochester did decline while this program was going on, it ended during the Great Depression, after a round of budget cuts and Goaler's retirement to return to Michigan. There was a proposal to pass a state law mandating the addition of iodine to salt, but there were a number of worries, in my opinion, well founded worries that people would object to a legal mandate that required something to be added to their food. So instead, health authorities in Michigan started a campaign of public education and a sort of industry pr campaign similar to what had happened in Switzerland, to convince all of the cantons to sell idise salt. This involved almost two hundred public health lectures that were carried out all over the state and work with the Michigan Salt Producers Association and outreach to the presidents of all the individual salt producers that were selling their products in Michigan. These folks were nicknamed the Saltmen. 00:25:13 Speaker 3: This became a. 00:25:14 Speaker 1: Huge cooperative effort between Michigan's public health workers and the salt industry, with David Marie Cowie being a major presence in all of it. Officials had to convince the salt industry that adding iodine wouldn't affect the quality of their product. They even brought in William Hale of Dow Chemical Company to demonstrate that it would not change the salt's flavor or function. They worked at a process for adding the iodine at a step into process when magnesia was already being added to keep the salt free flowing, and that cut down on the costs involved. They also had to do some outreach within the medical community to try to reassure doctors that adding iodine to the salt would not just flip the situation and cause an epidemic of hype thyroidism instead of hypothyroidism. That bit is a little more complicated. The amount of iodine that was to be added to the salt was nowhere near enough to cause hyper thyroidism in somebody whose thyroid was actually working properly, but it was enough to cause problems in people who were already experiencing serious thyroid dysfunction. According to a paper published in the Journal of the European Economic Association in twenty seventeen. Iodization may have contributed to as many as ten thousand deaths in the United States between nineteen twenty five and nineteen forty two, primarily among people who had been chronically iodine deficient for a very long time like many years. Officials in Michigan also wanted to be able to clearly document whether this whole effort was working, so they set up a research program to evaluate the effects of iodized salt. This started with a baseline survey of the rates of guaiter and other thyroid issues before iodized salt became available in stores, with follow ups to see how things changed after people had access to iodized salt. A lot of this was happening in late nineteen twenty three, and on March fifteenth, nineteen twenty four, the Michigan State Medical Society publicly endorsed the use of salt that contained zero point zero one percent sodium iodide. Six different companies selling salt in Michigan had their iodized products ready to go that May. Morton was something of a latecomer. There were executives who had concerns about producing iodized salt for only a couple of states if that salt was not also being used in all of the other states. 00:27:44 Speaker 2: Morton started selling iodized salt a few months after everyone else, and by the fall of that year, iodized salt was available in stores all across the United States. In most places in the US, iodized and non iodized salt were both sold into stores, but thanks to extensive public education campaigns and advertising on the part of the salt companies, most people who had access to iodized salt bought it. Follow Up studies in Michigan showed that once iodized salt was widely available, incidents of enlarged thyroids dropped by up to ninety percent. By nineteen thirty two, between ninety and ninety five percent of salt sold in Michigan was iodized, so by the mid nineteen twenties, it was clear that iodine had an effect on the prevalence of goiter and on hypothyroidism, and that salt was an effective way to get enough iodine into people's diets, but people still didn't fully understand why this worked, including within the medical community. An international conference on goiter was held and burned in nineteen twenty seven, and causes for goiter that were proposed at this conference included intestinal parasites, poor hygiene, bad food, and contaminated drinking water. A lot of the experts cited these as the cause of goiter. While agreeing that the addition of iodine to the salt worked to treat that goiter, they concluded, though, that the iodine was killing the parasites or destroying whatever was contaminating the food or water. Even in nineteen thirty three, an article in Public Health Reports still characterized the cause of endemic goiter as the subject of speculation and of divergence of opinion. 00:29:31 Speaker 1: David Murray Cowie died on January twenty seventh, nineteen forty, after a coronary thrombosis. At that point, he had been working toward a national campaign for iodized salt. His replacement, Frederick B. Minor, continued toward that goal and helped establish an iodized Salt Committee at the American Public Health Association. Although bills were introduced to mandate iodized salt nationwide, none of them ever passed. 00:29:59 Speaker 2: Today, laws and standards around iodized salt vary widely from one country to another, but an estimated eighty eight percent of people around the world have access to iodized salt. For the most part, once a nation's salt iodization program is well established, people typically still have access to iodized salt even when war or some kind of other unrest disrupts other public health measures like vaccine programs. But that still means that around the world, more than nine hundred million people don't have access to iodized salt, and an estimated fifty million people have enlarged thyroid glands and possibly other concerns. Because of this, researchers have also looked for other ways to distribute iodine in places where iodized salt isn't practical for some reason or where there's some other issue going on. One example is the use of iodinated poppyseed oil in highland areas of New Guinea where iodine deficiency is particularly or adding iodine to irrigation water or animal feeds so that it makes its way into other foods. Interestingly, the twenty one nations that are currently reported as having insufficient iodine intake are scattered all over the world in a way that looks pretty random on a globe. This includes both rich and poor countries. In Europe, Asia, Africa, and Central America, and there are thirteen countries that have too much iodine, either from already abundant iodine in their diets or over iodization of the salt. Here in the United States, dietary iodine intake has been declining since the nineteen seventies. Some of this is because of concerns about the connection between sodium intake and hypertension, although the biggest sources of sodium in the typical American diet are processed foods that are not usually made with iodized salt, not the iodized table salt that people might be avoiding. But another reason is just an increasing preference for things like sea salt and kosher salt and Himalayan pink salt. These are typically not iodized, although there are some brands that do carry iodized versions of these products. 00:32:16 Speaker 1: At this point, a lot of people in the US are getting more of their iodine from dairy products than from table salt, which means the rising preference for non dairy milks is playing a part in this story as well. Whether a plant based milk contains iodine depends on what it is made of. Some of them use thickeners made from seaweed, although the iodine and the seaweed might not make it through the manufacturing process. 00:32:40 Speaker 2: In the United States, nutrition labels typically only list iodine content if that was added into the product, not if the iodine occurs naturally, and that can make it tricky to know how much iodine a person is actually getting, and this affects people who are trying to get enough iodine as well as people who need to avoid iodine. For example, people who are getting radioactive iodine treatment are typically advised to avoid iodine in their diets. Since we have a whole episode on the history of radio iodine treatment, we're gonna run that as a Saturday Classic because it overlaps with this. 00:33:16 Speaker 1: A little bit. Do you also have listener mail for us? I do have listener mail for us. It is from Jody. Jody wrote, Hi, Holly and Tracy. Usually I listened to your podcast weekday mornings when getting ready for work, but when I saw this week's lineup was food themed, I decided to spend my Saturday afternoon with you. What caught my eye was banana ketchup. This came on my radar a few years ago after I moved from the Florida Keys to Las Vegas, Nevada, where there's a much larger Filipino population. I'm also a canner and had to figure out what to do with the fifteen ish pounds of bananas that showed up with an Instacart order instead of the one bunch I was exp This was during the pandemic, so another quick sweetbread was out of the question. I look forward to reading more about Maria Rosa's story using your references as a guide. As for how my banana ketchup turned out, it was interesting. 00:34:15 Speaker 3: Lol. 00:34:16 Speaker 2: Here's the safe canning recipe I used. There's a link to a recipe for banana ketchup. A Filipino co worker tasted it and approved, but my brain had trouble making sense of the color and I couldn't eat it with fries. But I do make a beat ketchup that gets gobbled up, so I know that's just in my head. That being said, I do try to run a zero waste kitchen, so I use it as a base for barbecue sauce for grilled ribs, and my guests kept trying to figure out what the secret flavor was while licking their fingers attached for cat tacks are picks of our ten year old spicy cat Ella and almost four year old goofball Jazzber. My husband is a jazz musician, so Ella is named after Ella Fitzgerald, and Jazz has not stopped purring since we adopted him from a shelter. His eyes looked like green jasper. This cat's I like this. I'm looking at a picture of a black cat with a very startled expression. I don't know if this kitty cat is actually startled, but that's that's the way that it struck me. And then there's also other kitty cat, so I'm guessing this one is Ella. 00:35:29 Speaker 3: Ella is on a bookshelf. 00:35:32 Speaker 2: Posed in such a way that at first I thought this was like a cat figurine. 00:35:38 Speaker 3: No, it is the real cat on the bookshelf. Thank you so much. 00:35:42 Speaker 2: I'm so interested about number one hearing the that you know, somebody just needed to make some banana ketchup at home because of all of these extra bananas. And then it also reminded me of experience I had in the early pandemic years when I had an order from like a place that sold locally grown fruits and vegetables and things, and the it was described as a pound of halapeno peppers, and I was like, I don't think that can be right, don't I don't think I'm gonna get a whole pound of halapeno peppers. I did, so I made a bunch of infused vodka with because that was more holopenos than I needed at that moment. Uh So, thank you so much for that email. If you would like to send us a note about this or any other episode, where at History Podcasts at iHeartRadio dot com, and you can subscribe to the show on the iHeartRadio app and anywhere else you'd like to get your podcasts. Stuff you Missed in History Class is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favor shows.
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