Most kosher salt does not contain iodine. Unlike regular table salt, which has been fortified with iodine in the United States since the 1920s, kosher salt is typically made from sodium chloride alone. If you’ve switched from table salt to kosher salt for cooking, you’ve likely eliminated one of the most common dietary sources of iodine without realizing it.
Why Kosher Salt Skips the Iodine
Kosher salt was designed for a specific job: drawing moisture out of meat during the Jewish religious practice of kashering. Its large, coarse grains sit on the surface of meat without fully dissolving, pulling out fluids that are then partially reabsorbed along with the salt. That function depends on a clean, pure salt crystal. Additives like iodine, fluoride, or dextrose can introduce metallic or off-putting flavors, which is exactly why manufacturers leave them out.
The name “kosher salt” refers to this meat-preparation process, not to the salt itself being certified kosher. It’s essentially a kitchen-grade coarse salt, and its appeal to home cooks and professional chefs comes down to that same clean flavor profile. Many cooks prefer it precisely because it tastes like nothing but salt.
What the Major Brands Actually Contain
Diamond Crystal kosher salt is entirely free of additives. It contains sodium chloride and nothing else. Morton kosher salt includes a small amount of an anti-caking agent to keep the grains from clumping, but no iodine. Neither brand offers an iodized version of their kosher salt, and iodized kosher salt is essentially nonexistent on store shelves.
The anti-caking agents permitted in salt by the FDA include yellow prussiate of soda (limited to 13 parts per million) and iron ammonium citrate (limited to 25 parts per million). These are present in trace amounts and serve only to prevent clumping. They are not nutritional supplements and do not replace iodine.
Does This Matter for Your Health?
It can, depending on the rest of your diet. Adults need about 150 micrograms of iodine per day. Your thyroid gland relies on iodine to produce the hormones that regulate metabolism, energy, and growth. Too little iodine over time can lead to thyroid problems, including an enlarged thyroid (goiter) and, during pregnancy, developmental issues in the baby.
Iodized table salt was introduced specifically to prevent these deficiencies, and it worked remarkably well. But as more households have shifted to kosher salt, sea salt, and other specialty salts for everyday cooking, some nutrition researchers have flagged a potential gap. If kosher salt is the only salt in your kitchen and you don’t eat much seafood, dairy, or eggs, you could fall short on iodine without any obvious symptoms for months or years.
Where to Get Iodine Without Table Salt
Seaweed is the richest food source of iodine by a wide margin. Kelp, nori, kombu, and wakame all contain significant amounts, though the concentration varies. Fish, shrimp, and other seafood are reliable sources. Dairy products, including milk, yogurt, and cheese, contain iodine because of iodine-based sanitizers used in dairy processing and iodine in animal feed. Eggs also contribute a modest amount.
If your diet regularly includes a couple of these food groups, you’re likely getting enough iodine even without iodized salt. If you eat a vegan or dairy-free diet and cook exclusively with kosher salt, checking your iodine intake more carefully is worth the effort. A simple multivitamin typically covers the daily requirement.
Kosher Salt vs. Table Salt in Recipes
Beyond the iodine question, the difference between kosher salt and table salt matters every time you measure by volume. A tablespoon of standard table salt weighs about 23 grams. A tablespoon of Morton kosher salt weighs 16 grams, and a tablespoon of Diamond Crystal kosher salt weighs just 10 grams. That means using the same tablespoon measurement with different salts can dramatically change how salty your food turns out.
A practical conversion: 1 part table salt equals roughly 1.5 parts Morton kosher salt or 2 parts Diamond Crystal kosher salt. If a recipe specifies one type and you’re using another, adjusting the amount prevents oversalting or underseasoning. Weighing salt in grams instead of using volume measurements eliminates the guesswork entirely.