Made by evaporating ocean water, unrefined sea salt contains trace amounts of minerals, including magnesium, calcium, copper and iodine, but not enough to matter. Sea salt is seldom iodized, and highly refined sea salt is virtually identical to non-iodized table salt. Sea salt comes in many varieties with different colors and flavors, depending on where it’s harvested, and can be pricey. Some sea salts have larger crystals, so they may have less sodium per teaspoon.
This course-grained salt is used in koshering and curing meats, among other food preparations. Kosher salt typically has no additives, including iodine. It is not nutritionally better than regular salt, but because of the shape of the crystals, a teaspoon has less sodium than a teaspoon of regular (table) salt.
Be skeptical. Salt can’t be grown organically in the sense that plants can be, so there’s no USDA organic standard for it. But a few countries certify salt as organic if it has been harvested from unpolluted waters, contains no additives, and meets other processing guidelines. Organic salt is not more healthful than other salt, contains no iodine, and is expensive (about $10 a pound).
Usually from rock salt mined from mineral deposits, table salt is finely ground and refined; anti-caking agents are added to keep it free flowing. Iodized salt (fortified with iodine), introduced in 1922, is credited with nearly eliminating goiter (enlarged thyroid) in the U.S. Iodine is also essential for brain development.
Choose iodized table salt to be on the safe side. If you don’t, there are plenty of food sources of iodine—particularly seafood and dairy foods; most multivitamin/mineral supplements supply 150 micrograms of iodine, the daily value for adults. Whatever salt you use, limit sodium intake to 1,500 to 2,300 milligrams a day (a teaspoon of table salt contains that upper limit). But remember, about three-quarters of the salt you eat you never see—it comes from processed foods and restaurant meals, not your salt shaker.