Iodized salt is regular table salt with a small amount of iodine added to it. In the United States, each gram of iodized salt contains about 45 micrograms of iodine, a trace mineral your thyroid gland needs to function properly. It’s one of the most successful public health interventions in history, and for most people, it’s the primary source of dietary iodine.
Why Iodine Is Added to Salt
Your thyroid, the butterfly-shaped gland at the base of your neck, uses iodine as a raw ingredient to build thyroid hormones. These hormones regulate your metabolism, heart rate, body temperature, and brain development. Without enough iodine, the thyroid can’t produce adequate hormones, and it begins to swell as it works harder to compensate. That visible swelling is called a goiter.
Before the 1920s, iodine deficiency was widespread across the Great Lakes, Appalachian, and Northwestern regions of the U.S., an area known as the “goiter belt.” Between 26% and 70% of children in these regions had clinically visible goiters. Iodized salt first appeared on grocery shelves in Michigan on May 1, 1924, and the rates of goiter dropped dramatically within years.
How Iodized Salt Is Made
The iodine in table salt typically comes from potassium iodate, a stable iodine compound dissolved in water. During manufacturing, a diluted solution (usually 3 to 5%) is either sprayed onto the salt through fine nozzles or dripped into the salt during the crushing stage. The result is a uniform, barely detectable dose of iodine in every pinch. You can’t taste the difference between iodized and non-iodized salt.
How Much Iodine You Need
Adults need 150 micrograms of iodine per day. That’s a tiny amount, roughly what you’d get from a little over 3 grams (about half a teaspoon) of iodized salt. Children need less, while pregnant and breastfeeding women need considerably more:
- Children 1 to 8 years: 90 mcg per day
- Children 9 to 13 years: 120 mcg per day
- Adults and teens 14+: 150 mcg per day
- Pregnant women: 220 mcg per day (WHO recommends 250 mcg)
- Breastfeeding women: 290 mcg per day
Most people who use iodized salt regularly in cooking and at the table meet these requirements without thinking about it. Other good dietary sources include dairy products, eggs, seafood, and seaweed.
What Happens When You Don’t Get Enough
Iodine deficiency affects the entire body, but its most devastating effects are on the developing brain. When a pregnant woman doesn’t get enough iodine, her fetus can suffer irreversible brain damage and mental retardation. The risk of stillbirth, miscarriage, and congenital abnormalities also rises. Thyroid hormones play their most critical role during early fetal development, driving the growth and maturation of the brain and other organs.
In children, deficiency stunts physical growth and impairs mental function, lowering IQ scores. In adults, prolonged deficiency leads to hypothyroidism, leaving you fatigued, cold, constipated, and mentally sluggish, with a visibly enlarged thyroid. Globally, iodine deficiency remains a leading cause of preventable intellectual disability.
Despite the widespread availability of iodized salt, nearly 1 billion people worldwide still don’t consume it. About 89% of the global population uses salt with at least some iodine, which means roughly 11% remains unprotected.
Sea Salt, Pink Salt, and Kosher Salt
If your salt container doesn’t say “iodized,” it almost certainly contains very little iodine. Unfortified sea salt has only trace amounts. The same is true for Himalayan pink salt and kosher salt. These products are popular for their texture and flavor, but they are not reliable iodine sources. If you’ve switched entirely to a specialty salt, you may want to check whether you’re getting iodine elsewhere in your diet.
Can You Get Too Much Iodine?
The tolerable upper limit for iodine is 1,100 micrograms per day for adults. Exceeding that amount regularly can cause thyroid dysfunction, sometimes triggering the same problems (like hypothyroidism or thyroid inflammation) that deficiency causes. You’re unlikely to hit that ceiling from iodized salt alone. The real risk comes from concentrated sources like kelp supplements, which can contain several thousand micrograms in a single dose. The American Thyroid Association advises against taking iodine or kelp supplements exceeding 500 mcg daily.
Certain groups are more vulnerable to excess iodine: infants, older adults, pregnant and breastfeeding women, and anyone with an existing thyroid condition.
Storing Iodized Salt
Iodine in salt isn’t permanent. It gradually escapes under certain conditions, particularly moisture, heat, and direct sunlight. Research on iodized salt stability shows that moisture content is directly correlated with iodine loss, with the biggest drop happening within the first week of exposure. To preserve the iodine content, store your salt in a sealed container in a cool, dry place. An open bowl of iodized salt sitting next to a hot stove will lose its iodine faster than a closed container in a pantry.