Iodine has one job. The thyroid builds it into the hormones that run your metabolic rate, body temperature, and mood, and in a fetus, the wiring of the brain ¹. Iodine is scarce in inland and mountainous soil, so before fortification whole regions had visible goiter ². Adding iodine to table salt in the 1920s dropped Michigan's childhood goiter from about 38% to under 2% in a decade ².

The modern risk is the invisible kind. U.S. iodine levels have halved since the 1970s ³, and roughly half of pregnant women now sit below the adequacy threshold ⁴. Children of first-trimester iodine-deficient mothers scored lower on reading and verbal IQ at ages 8–9 ⁵.

Sea salt does contain iodine, just almost none. Iodized table salt carries about 45 micrograms per gram; sea salt, fleur de sel, and Himalayan pink all come in under two ⁶. To match one quarter-teaspoon of iodized salt you'd eat twenty-plus of the boutique kind. The Himalayan "eighty-four trace minerals" are real and meaningless; the one mineral that matters at kitchen doses is the one it leaves out.

Make iodized salt the everyday salt. The front label says "iodized" or it doesn't. A quarter-teaspoon covers about half the daily requirement; cooking gets you the rest.

Two groups should care most. Pregnant, planning, or breastfeeding women: the fetal brain runs on the mother's iodine through the first trimester, and those wiring decisions don't get re-made ⁸. And anyone dropping the American backup sources of dairy, eggs, and seafood, since dairy is the second iodine pathway into the diet ³. Going vegan or dairy-free without a replacement lands you in the deficient range ⁹.