Let me give you a bit of background before I answer your question directly. Humans require trace amounts of iodine, a non-metallic mineral, for proper development and growth. It exists in most soils, and is absorbed by plants, which are in turn ingested by humans and animals. The thyroid gland is home to the body’s largest iodine stores, as it requires the mineral for synthesis of the hormones it secretes. That’s why an iodine deficiency can lead to an enlarged thyroid gland (endemic goiter), slowed metabolism, weight gain, and other symptoms of hypothyroidism, including fatigue, and intolerance of cold. Additionally, a deficiency can also promote neurological, gastrointestinal, and skin abnormalities. It proves even more vital for pregnant or nursing mothers whose thyroid problems from an iodine deficiency can impede fetal and child development. In fact, this prenatal deficiency is the most common cause of preventable brain damage in the world.
Iodized salt (or table salt) was first sold in the United States in 1924 in efforts to thwart goiter, an issue plaguing the country’s “goiter belt” – stretching from the areas surrounding the Great Lakes to the Pacific Northwest. While humanitarian efforts are making an impact, goiters and other health problems resulting from iodine deficiency are still common in parts of South America’s highlands, and areas within central Asia and Africa – where iodine was either drained from the soil by glaciation and flooding, or located far from ocean waters.
We can get iodine naturally by eating saltwater fish and seafood, kelp, and other sea vegetables, as well as vegetables grown in iodine-rich soils. Even dairy products can provide iodine if the animals graze on plants growing in soils containing iodine.
Conversely, the salt found in processed and fast foods is not iodized, with so much of our population substituting clean meals made from whole foods with take-out food or processed foods, iodine intakes in the United States have declined from about 250 micrograms (mcg) per day to 164 mcg daily. At a minimum, we need 150 mcg and the recommendation for pregnant and lactating women are at least 220 mcg and 290 mcg respectively. Daily intakes of up to 1,100 mcg, including that from iodized salt, are considered safe for adults. But the amount for children is less, with the maximum amounts being 200 mcg for ages 1-3; 300 mcg for ages 4-8; 600 mcg for ages 9-13; and 900 for teens age 14-18.
If you are eating a healthy, balanced, varied diet, you’re probably getting enough iodine and don’t need to use iodized salt. To enhance flavor you can alternatively opt for gourmet salts, which are often non-iodized and contain other beneficial trace minerals. Or try sea salt, which contains only small amounts of iodine. I use both unrefined (gray) and refined (white) sea salt instead of commercial salts, which often contain additives I don’t like, such as aluminum compounds to prevent caking.
Andrew Weil, M.D.