Many areas of the country have very little iodine in the soil. As a result, crops in these areas and animals raised on these crops are not exposed to much iodine. Before iodine was added to table salt, many people in these areas had goiter. The Lake Michigan area was once called the “goiter belt.” This problem has mostly gone away now. This is likely because of iodized salt and the widespread consumption of ocean fish and shellfish.
But people living in areas without enough iodine in the soil may still need iodine supplements. This includes people living in the Great Lakes states and mountain regions of the U.S. and Mexico.
Adults who don't get enough iodine in their diet can get goiter. In severe cases, this may lead to an underactive thyroid gland (hypothyroidism). Symptoms can include:
- Memory and cognitive issues.
- Decreased alertness.
- Dry skin and hair.
- Weight gain.
People who consume large amounts of soy, cassava, or uncooked cruciferous vegetables also need more iodine. These include cabbage, cauliflower, broccoli, kale, Brussels sprouts, and rutabagas. These foods have substances that keep the digestive tract from absorbing iodine. Cooking stops the action of these substances.
Newborn babies who don't get enough iodine in the womb are often born with enlarged thyroid glands. They may also have signs of hypothyroidism. If a baby's thyroid doesn't work during growth in the uterus, they can get congenital hypothyroidism. This can lead to intellectual issues. It can also cause growth problems.
Iodine is measured in micrograms (mcg). The recommended dietary allowance (RDA) is as follows:
|
Group
|
RDA
|
|
Infants (0 to 6 months)
|
110 mcg*
|
|
Infants (7 months to 1 year)
|
130 mcg*
|
|
Children (1 to 3 years)
|
90 mcg
|
|
Children (4 to 8 years)
|
90 mcg
|
|
Children (9 to 13 years)
|
120 mcg
|
|
Males (14 years and older)
|
150 mcg
|
|
Females (14 years and older)
|
150 mcg
|
|
Pregnant people
|
220 mcg
|
|
Breastfeeding people
|
290 mcg
|
*Adequate Intake (AI)
|
Food source
|
Nutrient content
|
|
Seaweed, dried, 2 tablespoons
|
116 mcg
|
|
Iodized table salt, ¼ teaspoon
|
76 mcg
|
|
Egg, hard boiled, 1 large
|
31 mcg
|
|
Cheese, cheddar, 1 ounce
|
15 mcg
|
|
Sea salt, non-iodized, ¼ teaspoon
|
<1 mcg
|
Iodized salt contains potassium iodide. It's often in a ratio of 1 part iodine to 10,000–100,000 parts salt. This means there's very little iodine in the salt. But it's enough to prevent goiter. Iodized salt made in the U.S. contains 76 mcg to 100 mcg of iodine per gram of salt.