If your kitchen salt looks fancier than the salt you grew up with, check the label.
Sea salt, kosher salt, Himalayan pink salt and other specialty salts can all season dinner perfectly well. But most are not iodized. That matters because iodine is one of those small nutrients doing a very large job: your thyroid uses it to make the hormones that help regulate metabolism.
For most Americans, iodine deficiency is uncommon. This is not a crisis article. It is a label-reading article, especially for runners who sweat a lot, eat little dairy or seafood, or have quietly replaced iodized table salt with something prettier.
What iodine actually does
Iodine is an essential component of the thyroid hormones T4 and T3. Those hormones help regulate metabolic activity throughout the body, including protein synthesis and enzyme activity. Adults need 150 micrograms of iodine per day. The recommendation rises to 220 micrograms during pregnancy and 290 micrograms during lactation.
That is the first important distinction: iodine supports normal physiology. It is not a pre-workout, and there is no good evidence that taking extra iodine makes an iodine-sufficient runner faster. Correcting a deficiency and boosting performance above normal are two very different claims.
The United States population is generally iodine sufficient. Still, the National Institutes of Health identifies a few groups more likely to fall short: people who do not use iodized salt, vegans, and people who eat little or no dairy, seafood or eggs. Plant-based milk substitutes often contain much less iodine than dairy milk unless they are fortified.
The salt switch runners may miss
Here is the odd part. Most of the sodium Americans eat comes from processed food, but food manufacturers almost always use noniodized salt. Meanwhile, many home cooks have moved from iodized table salt to sea salt, kosher salt or Himalayan salt. Those salts are usually not iodized either.
In other words, eating plenty of salt does not guarantee you are getting iodine.
According to the NIH, one-quarter teaspoon of iodized table salt provides about 78 micrograms of iodine, roughly half the adult Daily Value. The same amount of noniodized sea salt provides virtually none. This is not a reason to pour more salt on your food. It is a reason to notice which salt you already use and to consider iodine from the rest of your diet.
Does running increase iodine needs?
Iodine does appear in sweat, so a long run in Atlanta in August is not identical to sitting in air conditioning. But the athlete-specific evidence is thin and old, which is worth saying plainly.
A small 1985 study measured sweat iodine during treadmill exercise and reported concentrations around 37 micrograms per liter. A 1990 study of 13 male athletes found a similar average and suggested that total iodine loss rises with sweat volume. Those studies show that sweat loss is real. They do not establish a special iodine requirement for runners, and current U.S. recommendations do not give endurance athletes a separate daily target.
So the practical conclusion is modest: heavy sweaters should not assume iodine is irrelevant, but they also should not chase sweat losses with high-dose iodine supplements. Start with the ordinary adult target and a realistic look at your food pattern.
Useful food sources of iodine
Iodine content varies more than you might expect. The amount in dairy depends partly on farming and processing practices. Seaweed can range from sensible to enormous amounts. Even bread may contain a lot or almost none depending on whether the baker used an iodate dough conditioner.
| Food | Serving | Approximate iodine |
|---|---|---|
| Baked cod | 3 ounces | 146 mcg |
| Plain nonfat Greek yogurt | 3/4 cup | 87 mcg |
| Nonfat milk | 1 cup | 84 mcg |
| Iodized table salt | 1/4 teaspoon | 78 mcg |
| Hard-boiled egg | 1 large | 31 mcg |
| Noniodized sea salt | 1/4 teaspoon | 0 mcg |
These numbers are useful guides, not laboratory guarantees. If you eat dairy, eggs or seafood regularly and use iodized salt, you may already cover the basics without thinking about it. If you avoid all four, iodine deserves a closer look.
A simple iodine check for runners
1. Read the salt label
Look for the word “iodized” or iodine in the ingredient statement. Do not assume sea salt or pink salt contains meaningful iodine just because it came from the sea or a mountain.
2. Look at your usual week, not one perfect day
Do you regularly eat fish, yogurt, milk or eggs? Is your plant-based milk fortified with iodine? A repeatable routine matters more than building one iodine-themed dinner.
3. Be careful with kelp
Seaweed can contain very high and highly variable amounts of iodine. More is not better. The adult Tolerable Upper Intake Level is 1,100 micrograms per day, and excessive iodine can also disrupt thyroid function in susceptible people.
4. Do not diagnose yourself from fatigue
Fatigue, feeling cold and sluggish workouts can have many causes. A single spot urine iodine test is useful for population research but is not reliable for diagnosing an individual. If you have thyroid concerns, take them to a clinician instead of treating them with a high-dose supplement.
FAQ
Should runners take an iodine supplement?
Not automatically. Most U.S. adults get enough iodine, and there is no established extra requirement for runners. People who avoid iodized salt, dairy, eggs and seafood may want to review their intake with a qualified professional.
Is sea salt healthier than iodized salt?
They are both salt. The meaningful iodine difference is whether the product is iodized. Specialty salts are usually not.
Can iodine improve running performance?
Iodine is necessary for normal thyroid hormone production, but that does not make extra iodine a performance enhancer. The studies on sweat measured iodine loss, not faster race times from supplementation.
The bottom line
Iodine is not flashy, which may be why it is easy to overlook. Most runners probably get enough. But if your diet is dairy-free, seafood-free and egg-free, and your salt came in a stylish pouch that never says “iodized,” check the gap.
The goal is not more iodine. It is enough iodine, consistently, so the machinery can do its quiet work while you get on with yours.
This article is for general educational purposes and is not medical advice. Dietary supplements are not intended to diagnose, treat, cure or prevent disease. Talk with a qualified healthcare professional about individual needs, thyroid conditions, pregnancy, medications or supplementation.