The Quiet Mineral Your Thyroid Can’t Work Without: A Foor-First Guice to Iodine and Thyroid Health

What iodine actually does in your body, why deficiency is quietly climbing in the U.S., and how food — not supplements — is the right place to start

There is a mineral in your body so quietly essential that most people have no idea they might be low. No one talks about it the way they talk about magnesium or vitamin D. It doesn’t make headlines. It doesn’t show up on most standard lab panels. And yet without it, your thyroid literally cannot do its job.

That mineral is iodine.

We have been teaching on whole-food, plant-centered eating for decades, and iodine is one of those topics that seems simple on the surface and gets genuinely important the deeper you go. It is one of the few nutrients the body cannot make at all — it has to come from what you eat. And the American food supply has been delivering less and less of it for the past fifty years.

Our position throughout this article is food first. Iodine is not a nutrient that calls for a supplement protocol. It calls for an honest look at what you’re eating and whether whole, iodine-rich foods have a place in your diet. For most people, that is where the answer lives.

Why Iodine Is Not Optional

Your thyroid is a small, butterfly-shaped gland at the base of your throat. Its job is to produce hormones that set the pace for virtually every system in your body — how fast your heart beats, how efficiently you burn energy, how well you handle temperature, how clearly you think. Two of these hormones are called T4 and T3.

Here is the part that matters: iodine is the actual building block those hormones are made from. T4 contains four iodine atoms. T3 contains three. There is no substitute, no workaround. Without enough iodine coming in from food, the thyroid cannot make the hormones the rest of the body depends on.

Think of it this way: iodine isn’t something that helps the thyroid work better. It is the raw material the thyroid is built from. No iodine means no thyroid hormone. It really is that direct.

When iodine runs chronically short, the thyroid compensates. It grows, reaching further, trying to capture more from whatever blood passes through. The result is what was historically called goiter — a visibly enlarged thyroid that was once so common in the inland United States that the Great Lakes region earned the name “Goiter Belt.” Iodized salt programs, which began in 1924, largely fixed this. But iodine adequacy in the U.S. is no longer the given it once was.

Globally, iodine deficiency remains the most common preventable cause of brain damage. In regions without food fortification, the effects on child development — particularly in the womb — are severe and irreversible. That this is entirely preventable through food makes it one of the more sobering stories in nutrition.

Getting Iodine From Food: The Right Place to Start

Before we talk about what happens when iodine is low, we want to start where we always start — with food. Because for most people, the answer to iodine isn’t a supplement. It is a more thoughtful look at what whole foods you’re already eating and whether iodine-rich choices are among them.

Iodine is not evenly distributed across foods. It is concentrated in a specific set of whole foods, most of them from the sea or from animals that ate iodine-rich diets. Here are the best sources worth knowing:

• Wild-caught fish, especially cod, which provides around 99 micrograms in a 3-ounce serving — one of the most concentrated food sources available

• Plain yogurt and cow’s milk — a cup of either provides a meaningful portion of daily needs from dairy that naturally concentrates iodine

• Eggs — a simple, accessible source, with around 24 micrograms each

• Shrimp and other shellfish — concentrated sources of marine iodine

• Seaweed — particularly nori, which we’ll discuss in a moment

A diet that includes seafood and dairy a few times a week, built around a variety of whole foods, is likely providing reasonable iodine naturally. This is what food-first iodine nutrition looks like in practice. The challenge — and it is a real one — is that several trends in health-conscious eating have quietly removed these sources from the plate.

Seaweed: A Genuine Food-First Option

Seaweed has fed coastal populations for thousands of years and is one of the most iodine-rich whole foods on earth. We want to talk about it warmly, because the plant-based community sometimes treats it with more caution than it deserves — at least for certain varieties.

Nori — the thin, dark sheets used to wrap sushi — is an excellent culinary iodine source. One to two sheets provides a meaningful contribution to daily iodine needs and fits naturally into everyday eating. Wakame, the tender green seaweed common in miso soup and salads, is another reasonable option with a gentler iodine content. These are everyday foods in Japan and across much of East Asia, and they are worth embracing as part of a food-first approach to iodine.

Brown seaweeds like kelp and kombu are a different story. Their iodine content varies enormously depending on species, harvest location, and season — sometimes by a factor of twenty or more within the same category. A small amount of dried kombu can occasionally deliver far more iodine than intended. These are wonderful culinary ingredients used judiciously in broths and cooking, but they are not the right tool for consistent daily iodine support in the way nori and wakame are.

Nori and wakame are everyday foods with a long history of safe, consistent use. Embracing them as part of regular eating is a genuinely food-first approach to iodine — one that has nourished some of the world’s healthiest populations for generations.

What Japan Tells Us

Japan is one of the most compelling real-world examples of what food-rich iodine intake looks like at a population scale — and it is a story we think gets overlooked in Western nutrition conversations.

The Japanese diet is rich in seafood and sea vegetables, particularly nori, wakame, and kombu used in dashi broths and everyday cooking. Estimates suggest average iodine intake in Japan runs somewhere between three and ten times higher than in the United States, depending on the region and dietary patterns. Japanese populations have eaten this way for centuries.

What is striking is the health picture. Japan has historically had lower rates of breast cancer and fibrocystic breast disease than Western populations. Despite iodine intakes that far exceed standard Western recommendations, Japan does not show a population-level epidemic of thyroid problems. The body, when nourished by whole food rather than isolated supplements, appears to handle generous iodine intake as part of a complete dietary pattern in a fundamentally different way than high-dose supplementation.

This is not proof that high iodine is protective in isolation — the Japanese diet involves many factors. But it is a meaningful real-world signal that food-form iodine, eaten as part of a traditional whole-food diet, is handled well by the body across generations. That is the food-first case for embracing iodine-rich whole foods rather than treating iodine as a problem to be solved with a capsule.

What’s Happened to Iodine in the American Diet

Despite iodine being readily available in nature, Americans have been getting progressively less of it for the past five decades. In the early 1970s, iodine levels were comfortably adequate across the population. By the most recent national surveys, that has changed significantly.

Several things happened at once. Iodine was removed from commercial bread in the 1980s and replaced with a bromine-based additive. The sanitizing solutions used in dairy processing — which had been a significant source of iodine in milk — were changed. As health-conscious eaters shifted toward low-sodium diets, they used less iodized salt. And as plant-based eating expanded, more people quietly eliminated dairy and seafood — the two food categories that had been quietly carrying most of the iodine load.

Perhaps most significantly: many people who eat thoughtfully have switched from refined iodized table salt to premium unrefined sea salts and Himalayan pink salt — which are genuinely better choices in most respects, but contain negligible iodine. This one shift alone can quietly eliminate a person’s primary dietary iodine source without them realizing it.

The Numbers Behind the Trend

A 2025 study in the Journal of Nutrition examined national health survey data from more than 22,000 Americans over nearly two decades. Inadequate iodine status increased continuously from 2001 through 2018. By 2017–2018, 35 percent of women of reproductive age had inadequate iodine intake. For pregnant women, that figure was 46 percent.

The 2025–2030 U.S. Dietary Guidelines Advisory Committee formally designated iodine as a “nutrient of concern” — particularly for pregnant women, breastfeeding mothers, and women of reproductive age. That is not a designation that gets made without meaningful evidence of population-level insufficiency.

This is not a dramatic crisis. It is a slow-building gap that takes years to show up, and when it does, it often looks like something else — persistent fatigue, cold sensitivity, slow thinking, weight that won’t budge. These are thyroid symptoms. And iodine is often part of the picture.

Iodine Beyond the Thyroid

Most conversations about iodine stop at the thyroid. That is where the evidence is strongest and the stakes are clearest. But iodine has a role in other tissues throughout the body that doesn’t get nearly enough attention.

The same mechanism that carries iodine into thyroid cells is also found in the salivary glands, the stomach lining, breast tissue, the ovaries, and the prostate. Iodine is actively taken up and concentrated in these tissues. In the breast especially, this has attracted significant research interest.

Breast Health and the Fibrocystic Connection

Three clinical trials involving more than 2,200 women looked at a specific form of iodine called molecular iodine — a different form than what is found in most food or supplements — as a treatment for fibrocystic breast changes. Fibrocystic breast changes are the benign but often painful lumpy tissue that affects a large number of women, particularly in the years before menopause.

In those trials, molecular iodine produced meaningful improvement in 65 to 74 percent of cases. In the most detailed study, 98 percent of women treated for nine months were pain-free by the end, with nearly 72 percent showing measurable structural improvement. The placebo response in those same studies was 33 percent.

The mechanism appears to involve how this form of iodine interacts with breast tissue cells — encouraging them to mature normally and complete their natural life cycle rather than accumulating. This is worth knowing, particularly for women who have dealt with fibrocystic breast changes.

The connection to breast cancer is more preliminary. Japanese women, who eat substantially more iodine through seaweed than most Western populations, have historically had lower breast cancer rates. Animal studies and small human trials show interesting signals. This is promising and worth watching, though it is not yet the kind of evidence that supports a clinical recommendation.

Pregnancy: Where This Matters Most

The stakes for iodine during pregnancy deserve special attention. Until around the twentieth week of pregnancy, the developing baby relies entirely on the mother’s thyroid hormones for brain development. The baby’s own thyroid is not yet functioning. Every neural connection being formed depends on what the mother’s body can supply — and that depends on her iodine status.

When a mother’s iodine is severely low during pregnancy, the effects on the child’s brain development can be profound and irreversible. Countries with effective food fortification programs have largely eliminated the worst outcomes. But there is no sharp line between “enough” and “not enough.” Even mild-to-moderate shortfall during pregnancy carries quieter costs.

A study following more than 1,000 mother-child pairs in the United Kingdom found that women with low iodine in the first trimester were significantly more likely to have children with lower verbal scores, reduced reading accuracy, and impaired reading comprehension at age eight. Consistent, measurable, and preventable.

Not all prenatal vitamins contain iodine, and this is not a small oversight. If you are pregnant or planning to become pregnant, check the label of your prenatal specifically. Iodine should be listed, ideally as potassium iodide. If it is not there, this is worth discussing with your care provider.

Seafood and dairy eaten regularly through pregnancy are the food-first way to support iodine needs. For women not eating these foods, attention to iodine sources matters more, and a prenatal that includes iodine becomes more important.

What Competes With Iodine in the Modern Environment

Iodine belongs to a chemical family called halogens — along with fluorine, chlorine, and bromine. This matters because other members of this chemical family can compete with iodine for entry into the thyroid and other tissues. Think of it as a doorway that only fits certain shapes — when that doorway is occupied by a competing compound, iodine can’t get through.

Perchlorate: The Best-Documented Concern

Perchlorate is a compound found in fertilizers, fireworks, and rocket fuel that has contaminated groundwater in many parts of the United States. It competes for the same entry point as iodine in the thyroid, and it competes aggressively — roughly 30 times more tightly than iodine itself. This is well-established science. Environmental nitrate from agricultural runoff and drinking water also competes through the same pathway.

Bromide and Fluoride

When iodine was removed from commercial bread in the 1980s, potassium bromate — a bromine compound — was added as a replacement. Bromide also appears in many flame retardants that accumulate in household dust over time. Bromide competes with iodine in the body and can interfere with iodine’s normal function in tissues.

Fluoride has been shown in laboratory settings to interfere with iodine transport. At the levels found in most municipal water, human studies have not confirmed significant thyroid effects in healthy people, but the mechanistic concern is real and actively studied.

The practical takeaway: if your iodine intake from food is already low, minimizing these competing exposures makes good sense. Filtered water, choosing whole foods over highly processed products, and focusing on iodine-rich eating are practical, low-risk choices that become more meaningful when iodine status is already suboptimal.

Hashimoto’s: Where This Gets More Personal

If you have Hashimoto’s thyroiditis — the autoimmune condition where the immune system attacks thyroid tissue — iodine deserves more careful attention than it does for most people. The guidance you encounter may feel contradictory, because both too little and too much iodine can cause problems when the thyroid is already under autoimmune stress.

Here is what the research supports. Iodine in excess, particularly from supplements at high doses, appears to trigger or worsen autoimmune inflammation in people who are predisposed to it. The reason involves a byproduct called hydrogen peroxide that the thyroid naturally generates when making hormones. In a healthy thyroid this byproduct is quickly neutralized. In Hashimoto’s, that process is already impaired, so extra iodine can add extra stress to a system that is already struggling.

At the same time, restricting iodine dramatically is not the answer. Some Hashimoto’s patients are genuinely deficient and worsen with restriction. Getting adequate iodine from food — dairy, seafood, nori, eggs — while avoiding high-dose supplementation is the sensible middle ground. If you have Hashimoto’s and are considering iodine supplementation, working with a practitioner who understands this territory is genuinely important.

Selenium: Iodine’s Essential Partner

This section represents our position, not just a general observation: if you are taking supplemental iodine, you should be getting selenium alongside it. And even if you are getting iodine primarily from food, selenium is worth paying attention to for thyroid health.

Here is the reason. Every time your thyroid makes thyroid hormone, it generates hydrogen peroxide as a natural byproduct of the process. Selenium is required by the enzymes that neutralize that hydrogen peroxide before it can damage thyroid cells. Selenium is also required to convert T4 — the form your thyroid makes — into T3, the active form your cells actually use. These are not minor supporting roles. They are essential.

When selenium is low and iodine is adequate or high, the thyroid is in a difficult position: making hormones, generating the byproduct, but missing the cleanup crew. The damage accumulates slowly. For people without thyroid disease this may be gradual and quiet. For people with Hashimoto’s, it can meaningfully accelerate the autoimmune process.

Research shows that Hashimoto’s patients with low selenium who increase their intake can reduce thyroid antibody levels by nearly 64 percent. That is a significant response to a single nutrient. A 2024 meta-analysis in the journal Thyroid confirmed this across multiple randomized controlled trials.

Iodine and selenium are a pair. Taking iodine without ensuring selenium is like fueling a furnace without maintaining the ventilation system. The process runs, but without the protection, things wear down. One to two Brazil nuts a day is one of the simplest and most food-consistent ways to keep selenium where it needs to be.

Getting Selenium From Food

Brazil nuts are the most concentrated food source of selenium you can eat. One to two a day provides generous selenium in a form the body recognizes — this is our preferred approach because it is whole-food, it is practical, and it is easy to sustain as a daily habit.

Other good food sources include wild-caught fish like tuna, halibut, and sardines, eggs, and certain mushrooms. The selenium content of most plant foods varies considerably depending on the soil they were grown in, which is why Brazil nuts — which accumulate selenium reliably regardless of soil variation — are such a consistent choice.

Plant-Based Eating and the Iodine Gap

We have taught plant-centered eating for most of our adult lives. We believe food is medicine and that the body is designed to thrive on whole, living foods. And part of that teaching is being honest about where plant-forward eating creates specific nutritional gaps that deserve attention. Iodine is one of them.

A 2023 systematic review found that the average iodine intake of vegans was approximately 17 micrograms per day, against a daily need of around 150 micrograms. That is roughly 11 percent of what the body needs. Multiple studies find that people eating fully plant-based diets tend to run low on iodine compared to people who include dairy and seafood.

The reason is straightforward. The two biggest dietary iodine sources in the American food supply are dairy and seafood — both absent from vegan eating. Plant foods themselves contain very little iodine, and what they do contain depends on the iodine content of the soil where they were grown, which varies enormously and has generally declined with industrial farming.

For plant-based eaters, nori and wakame eaten regularly are the most practical food-first bridge. If seaweed is not part of your regular eating, and dairy and seafood are not either, then a supplement providing iodine as potassium iodide fills the gap in a consistent way. This is not a daily prescription for everyone — it is a sensible response to a specific dietary reality.

A Word on Salt

Conventional iodized table salt does provide iodine, and iodized salt programs reversed the goiter epidemic of the early 20th century. But refined table salt is not something we recommend as a health strategy. The processing strips trace minerals, and relying on a heavily refined product to solve a nutritional gap is not a food-first approach.

The more important point is this: many health-conscious people have already made the switch to unrefined sea salts and Himalayan pink salt — which are better choices in most respects but contain negligible iodine. If this is you, and if you are not eating seafood, dairy, or seaweed regularly, you may have quietly eliminated your main iodine source without realizing it. That is the gap worth closing — and the answer is building iodine-rich whole foods back into your eating, not returning to refined table salt.

When Supplementation Makes Sense

We want to be clear about where we stand: supplemental iodine is not something everyone needs. The priority is always food first. But for people whose diet genuinely does not provide enough iodine — particularly those eating fully plant-based, those avoiding both dairy and seafood, and those who are pregnant or trying to become pregnant — being thoughtful about additional support is a reasonable act of stewardship.

For most healthy adults, the focus should be on building iodine-rich whole foods into regular eating: nori, seafood, eggs, dairy if you eat it. For plant-based eaters who are not regularly eating seaweed, a simple iodine supplement provides a consistent, reliable bridge. For pregnant women, ensuring a prenatal contains iodine is important regardless of diet.

Within integrative medicine, there is a body of clinical work proposing that the body’s full iodine needs — not just for the thyroid but for breast tissue, the ovaries, and other tissues — may be higher than standard recommendations suggest. Practitioners including David Brownstein MD have worked with higher doses in their clinical populations and reported meaningful results. This work is real and worth knowing about. It is also distinct from where we feel the evidence supports a general recommendation. We present it honestly without endorsing high-dose iodine supplementation for general use.

If you have Hashimoto’s, specific thyroid concerns, or are considering anything beyond basic dietary adequacy, working with a practitioner who knows this territory is genuinely important.

The Stewardship Lens

We don’t believe the goal of nutrition is to optimize every variable in isolation. The goal is to steward the body we have been given, wisely and sustainably, in a way that supports the life we are called to live.

Iodine is a nutrient that has quietly slipped out of the American food conversation even as its adequacy has declined. For most people, the answer is not a supplement protocol — it is a more honest look at whether iodine-rich whole foods have a real presence in your eating. Seafood. Eggs. Dairy. Nori and wakame. These are the foods the body was designed to receive iodine from. They come packaged with dozens of other nutrients that work together in ways an isolated supplement cannot replicate.

Japan has been showing us this for generations. Populations that eat seaweed and seafood as everyday foods are not struggling with iodine deficiency. They are thriving on it. That is the food-first picture of iodine done well.

Eat a wide variety of whole foods. Let seaweed have a real place in your eating if it doesn’t already. If you are plant-based and not getting iodine from food consistently, a simple supplement closes the gap. If you are pregnant or planning to be, check that your prenatal contains iodine. And pair iodine with selenium — through Brazil nuts, through fish, through eggs — because the two work together and always have.

QUESTIONS WE HEAR MOST OFTEN

What are the best foods to get iodine from?

The most concentrated food sources of iodine are wild-caught seafood (especially cod and shrimp), plain yogurt and cow’s milk, eggs, and sea vegetables — particularly nori and wakame. Nori sheets used in sushi are a practical everyday option that fits naturally into plant-centered eating and provides meaningful iodine without the variability of other seaweeds. Japanese and other East Asian populations have relied on nori and wakame as dietary staples for generations and show none of the iodine-related health problems that chronic deficiency produces. Building these foods into regular eating is the most sustainable approach to iodine nutrition.

Is seaweed a good source of iodine?

Yes — particularly nori and wakame, which are gentle, consistent sources that fit naturally into everyday cooking and eating. One to two nori sheets or a regular serving of wakame in soup or salad provides meaningful iodine in a whole-food form. Brown seaweeds like kelp and kombu have much more variable iodine content depending on species and harvest, which makes them better suited to occasional culinary use in broths than to daily iodine support. If seaweed is not part of your regular eating, it is worth adding — especially for those not eating dairy or seafood.

How do I know if I’m getting enough iodine?

The most practical first step is an honest look at your diet. If you eat seafood and dairy regularly, you are likely getting reasonable iodine from food. If you eat a plant-based diet, avoid both dairy and seafood, and do not eat nori or other sea vegetables regularly, your iodine intake may be low regardless of how healthy your overall diet is. Standard blood panels do not routinely test iodine. A urinary iodine test can give a general picture of status. Anyone with unexplained fatigue, cold sensitivity, hair thinning, weight changes, or a thyroid history is worth discussing iodine status with their doctor.

I eat a plant-based diet. What should I do about iodine?

Start with food. Nori and wakame eaten regularly are the most practical plant-based iodine sources and have a long history of consistent safe use in traditional diets. If seaweed is not a regular part of your eating, a simple iodine supplement fills the gap reliably. Pair whichever approach you use with selenium — one to two Brazil nuts a day is an easy food-first way to keep selenium adequate, which matters for how your thyroid handles iodine. Refined iodized table salt is not something we recommend as the primary solution, and unrefined sea salts and Himalayan salt contain negligible iodine.

If I’m taking supplemental iodine, why does selenium matter?

Every time your thyroid makes thyroid hormone, it generates a byproduct that can damage thyroid cells if it’s not neutralized. Selenium is required by the enzymes that do that neutralizing. It is also required to convert thyroid hormone from its storage form into the active form your cells actually use. When selenium is low and iodine is adequate or high, the thyroid is producing hormones but missing the protection it needs. One to two Brazil nuts a day provides selenium in a whole-food form that supports this partnership naturally. Iodine and selenium work together. Attending to both is part of how we think about thyroid stewardship.

I have Hashimoto’s. How should I think about iodine?

Getting adequate iodine from food — dairy, seafood, nori, eggs — while avoiding high-dose iodine supplementation is the sensible approach for most people with Hashimoto’s. The evidence supports adequate intake and shows problems with both extreme restriction and high-dose supplementation in people with autoimmune thyroid disease. Selenium matters especially for Hashimoto’s — research shows that raising selenium intake can meaningfully reduce thyroid antibody levels in people who are selenium-deficient. Working with a practitioner who understands this balance is genuinely worthwhile rather than trying to navigate it alone.

Should I check my prenatal vitamin for iodine?

Yes — and this is worth doing specifically rather than assuming. Many prenatal vitamins do not include iodine. Check the label for potassium iodide listed among the ingredients. If your prenatal does not contain iodine, and you are not eating seafood and dairy regularly, this is worth discussing with your care provider. Iodine during pregnancy matters for the baby’s brain development from very early in the first trimester, before many women even know they are pregnant. Food sources — seafood, dairy, nori — matter here too, and a varied whole-food diet is always the foundation.

Paul and Ann Malkmus write at AMPMforHealth.com— a faith-informed, food-first resource for people who want to go deeper than the standard health conversation. To explore related topics, read our articles on histamine and thyroid inflammation, gut B vitamins, and healthy aging.