All Episodes

June 5, 2024 37 mins

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.

See omnystudio.com/listener for privacy information.

Mark as Played
Transcript

Episode Transcript

Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:01):
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.

Speaker 2 (00:16):
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

(00:37):
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

(00:59):
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

(01:20):
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.

Speaker 1 (01:38):
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,

(02:00):
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

(02:20):
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

(02:43):
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,

(03:05):
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

(03:27):
consume moves from the digestive system to the blood and
from there to the thyroid gland, which produces those hormones.

Speaker 2 (03:35):
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

(03:59):
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

(04:23):
thousands and thousands of years.

Speaker 1 (04:25):
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.

Speaker 2 (04:46):
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

(05:07):
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.

Speaker 1 (05:28):
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

(05:48):
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.

Speaker 2 (05:56):
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

(06:18):
have even more difficulty getting enough iodine In people.

Speaker 1 (06:23):
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

(06:43):
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.

Speaker 3 (07:02):
Without enough iodine.

Speaker 2 (07:04):
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

(07:26):
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.

(07:50):
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

(08:12):
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

(08:32):
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

(08:56):
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

(09:18):
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

(09:40):
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,

(10:02):
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

(10:24):
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

(10:48):
to really experiment with this, so he gave a sample
to Joseph Luis Gaerusac.

Speaker 3 (10:53):
We talked about.

Speaker 2 (10:54):
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.

Speaker 1 (11:08):
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

(11:30):
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

(11:50):
response to treatment with iodine.

Speaker 2 (11:53):
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

(12:16):
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.

(12:40):
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

(13:02):
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.

(13:25):
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

(13:46):
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

(14:09):
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

(14:31):
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

(14:51):
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

(15:12):
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,

(15:33):
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.

(15:54):
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

(16:16):
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

(16:36):
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

(16:56):
of goiter were caused by a lack of iodie.

Speaker 3 (17:00):
In nineteen fourteen.

Speaker 2 (17:02):
There was again a lot of opposition to his ideas
of iodine supplementation, due to fears that that supplementation might
poison people.

Speaker 1 (17:10):
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

(17:32):
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.

Speaker 2 (17:48):
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.

(18:09):
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

(18:30):
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

(18:54):
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

(19:15):
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

(19:37):
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.

(20:03):
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

(20:24):
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.

Speaker 1 (20:33):
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.

Speaker 2 (20:54):
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

(21:17):
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

(21:38):
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,

(22:02):
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

(22:22):
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

(22:43):
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

(23:04):
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

(23:26):
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.

Speaker 1 (23:42):
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

(24:03):
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

(24:24):
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

(24:47):
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.

(25:10):
These folks were nicknamed the Saltmen.

Speaker 3 (25:13):
This became a.

Speaker 1 (25:14):
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

(25:35):
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

(25:56):
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

(26:17):
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

(26:41):
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

(27:04):
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

(27:26):
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.

Speaker 2 (27:44):
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,

(28:07):
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

(28:30):
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

(28:53):
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

(29:15):
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.

Speaker 1 (29:31):
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.

(29:53):
Although bills were introduced to mandate iodized salt nationwide, none
of them ever passed.

Speaker 2 (29:59):
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

(30:20):
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

(30:43):
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

(31:03):
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

(31:27):
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

(31:48):
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

(32:09):
are typically not iodized, although there are some brands that
do carry iodized versions of these products.

Speaker 1 (32:16):
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

(32:38):
make it through the manufacturing process.

Speaker 2 (32:40):
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.

(33:01):
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.

Speaker 1 (33:16):
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

(33:38):
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,

(34:02):
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.

Speaker 3 (34:15):
Lol.

Speaker 2 (34:16):
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

(34:39):
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

(35:01):
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,

(35:23):
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.

Speaker 3 (35:29):
Ella is on a bookshelf.

Speaker 2 (35:32):
Posed in such a way that at first I thought
this was like a cat figurine.

Speaker 3 (35:38):
No, it is the real cat on the bookshelf. Thank
you so much.

Speaker 2 (35:42):
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,

(36:07):
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

(36:29):
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

(36:51):
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.

Stuff You Missed in History Class News

Advertise With Us

Follow Us On

Hosts And Creators

Tracy V. Wilson

Tracy V. Wilson

Holly Frey

Holly Frey

Show Links

AboutStoreRSS

Popular Podcasts

Stuff You Should Know

Stuff You Should Know

If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.

The Nikki Glaser Podcast

The Nikki Glaser Podcast

Every week comedian and infamous roaster Nikki Glaser provides a fun, fast-paced, and brutally honest look into current pop-culture and her own personal life.

Music, radio and podcasts, all free. Listen online or download the iHeart App.

Connect

© 2024 iHeartMedia, Inc.