You probably don’t think twice about that blue cylinder of Morton’s in your pantry. It’s cheap. It’s everywhere. Honestly, it’s kinda boring. But that little pour-spout hides one of the most successful medical interventions in human history. We’re talking about why iodine added to salt became a global standard and why, despite all our modern health trends, it still actually matters for your brain.
Salt is salt, right? Not really.
Back in the early 1900s, the United States had a massive problem, specifically in the Great Lakes, Appalachians, and Northwest regions. They called it the "Goiter Belt." People were walking around with massive, visible swellings in their necks. These were goiters—enlarged thyroid glands gasping for iodine. It wasn't just an aesthetic issue either. Lack of iodine during pregnancy was causing severe developmental delays in children. It was a silent crisis of stunted growth and lowered IQs across entire swaths of the country.
The Michigan Experiment that Changed Everything
David Crile and David Marine were some of the early researchers who looked at this and realized something simple: the soil in these regions was stripped of iodine. If it’s not in the dirt, it’s not in the kale. If it’s not in the kale, it’s not in you. In 1924, Michigan became the testing ground for iodized salt.
It worked. Fast.
By 1951, the prevalence of goiter in some Michigan counties dropped from nearly 40% to practically zero. This wasn't some high-tech pharmaceutical breakthrough. It was just a trace mineral added to a seasoning everyone already used. The beauty of the plan was its simplicity. You didn't need people to go to a clinic or take a pill. They just had to season their eggs.
Why Your Thyroid is Obsessed with Iodine
Think of your thyroid as the furnace of your body. It sits in your neck, shaped like a butterfly, and it runs your metabolism. To do its job, it needs to produce hormones—specifically thyroxine ($T_4$) and triiodothyronine ($T_3$).
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Here is the kicker: iodine is the literal building block of these hormones.
The "4" and the "3" in those names actually refer to the number of iodine atoms attached. No iodine? No hormones. When your thyroid can't make enough, your brain sends a signal (TSH) to "work harder." The gland starts growing to try and catch any stray molecule of iodine it can find. That’s how you get a goiter.
But it goes deeper than just a neck lump. Hypothyroidism—the state of having an underactive thyroid—makes you feel like a zombie. You’re cold. You’re tired. Your hair thins. You get depressed. It’s basically like your body is trying to run on a dying battery.
The IQ Connection Most People Miss
The most compelling reason why iodine added to salt remains a priority for the World Health Organization (WHO) isn't actually about goiters. It’s about brains.
Iodine is absolutely critical for fetal brain development. Research, including a notable study published in The Journal of Economic Perspectives, suggested that the introduction of iodized salt in the 1920s might have actually boosted the average IQ in iodine-deficient areas by as much as 15 points. That is a massive demographic shift.
Even today, iodine deficiency remains the world’s leading cause of preventable intellectual disability. It’s a tragedy because it’s so easy to fix. Yet, as we move toward "fancy" salts and away from processed foods, we're seeing a weird resurgence of deficiency in developed nations.
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The Pink Himalayan Salt Trap
We need to talk about your kitchen aesthetic.
Lately, everyone has swapped their basic table salt for Pink Himalayan salt, sea salt, or Celtic salt. It looks better in a glass grinder. It feels more "natural." It’s trendy.
But here is the reality check: most of those specialty salts contain almost zero iodine.
Sea salt sounds like it should have iodine because it comes from the ocean, right? Nope. Most of the iodine is lost during the processing and evaporation. If you’ve completely ditched iodized table salt for the pink stuff, and you don't eat a ton of dairy or seaweed, you might actually be putting yourself at risk.
I’m not saying you need to throw away your expensive salt. Just realize that it’s a seasoning, not a supplement.
How Much Do You Actually Need?
The RDA (Recommended Dietary Allowance) for most adults is about 150 micrograms. If you’re pregnant, that jumps to 220, and 290 if you’re breastfeeding.
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Where do you get it if not from salt?
- Dairy: Cows are often given iodine supplements, and the sanitizers used on milking equipment contain it. So, a glass of milk is actually a solid source.
- Eggs: Most of the iodine is in the yolk.
- Seaweed: Nori, kombu, and wakame are iodine powerhouses. Be careful though—kombu can actually have too much, which can freak out your thyroid in the opposite direction.
- Cod and Shrimp: Seafood is generally great, assuming it’s not from a farm with weird nutritional profiles.
The Modern Risk: Is Deficiency Coming Back?
Public health experts are starting to worry. In the UK and parts of Australia, iodine levels have been dipping. Why? Because we’re drinking less cow’s milk and opting for almond or oat milk (which usually aren't fortified with iodine). We're eating less bread—commercial bread used to use "iodates" as dough conditioners, though many have switched to bromates, which can actually compete with iodine in your body.
Basically, we’ve gotten so good at "clean eating" that we’ve accidentally cleaned out a necessary micronutrient.
A Note on "Toxic" Salt
You’ll hear some corners of the internet claiming that table salt is "toxic" because it contains anti-caking agents like sodium ferrocyanide or calcium silicate. Honestly, the amounts are so small they’re effectively negligible for the average person. If you're really worried about additives, you can find non-GMO, organic iodized salts that skip the heavy chemicals but keep the iodine.
The trade-off is simple: a tiny bit of anti-caking agent versus the risk of thyroid dysfunction and developmental issues. For most, the choice is clear.
Actionable Steps for Your Kitchen
If you want to make sure your thyroid is actually happy, you don't need a radical overhaul.
- Check your labels. Look at your salt. If it doesn't say "iodized," it isn't. Keep a box of the cheap stuff for boiling pasta or baking bread.
- Diversify your minerals. Use your fancy pink salt for finishing a steak, but use iodized salt for your everyday cooking.
- Audit your dairy alternatives. If you’ve gone vegan or dairy-free, check if your milk alternative is fortified. If not, consider adding a little more seaweed or a targeted multivitamin to your routine.
- Watch for symptoms. If you're feeling chronically sluggish, cold, or notice your skin getting unusually dry, don't just "push through." Get a simple blood test for TSH and T4 levels.
Iodization was the original "biohack." It was a way to upgrade the human population without requiring a lifestyle revolution. We should probably stop trying to outsmart it just for the sake of a prettier salt shaker. Keep it simple. Keep it iodized.