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Iodine 

Other name(s):

iodide, organic iodine, potassium iodide, sodium iodide

General description

Iodine is an essential mineral element. It is naturally found in some foods, and added to other foods. It can also be taken as a supplement. In 1922, experts learned that the thyroid gland needs iodine. The gland needs it to make thyroid hormones and prevent enlarged thyroid glands (goiter). Thyroid hormones control metabolism. They also affect reproductive functions, nerves, muscles, skin, and hair. Iodine also helps make protein and use oxygen.

Iodine is in 2 main hormones made by the thyroid gland. Together, these hormones control the metabolic rate of the body. They’re important in growth and development, especially in an unborn baby and a newborn. Not having enough iodine and thyroid hormones can cause intellectual issues and developmental delays.

Medically valid uses

Iodine is used to prevent and treat:

  • Goiters

  • Over-active thyroid gland (hyperthyroidism)

  • Iodine deficiency

  • Thyrotoxic crisis

Using table salt that has potassium iodide can help prevent goiters. Other sources of iodine include eggs, dairy foods, and seaweed.

If you get goiter during pregnancy, you’ll need treatment. This can keep your baby healthy.  

Unsubstantiated claims

There may be benefits that have not yet been proven through research.

Iodine may help immune response. And it may have a helpful effect on mammary dysplasia and fibrocystic breast disease.

Recommended intake

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 goiters. 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 United States and Mexico.

Adults who don’t get enough iodine in their diet can get goiters. 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 that 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 womb, he or she 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 (1–3 years)

90 mcg

Children (4–8 years)

90 mcg

Children (9–13 years)

120 mcg

Males (14 years and older)

150 mcg

Females (14 years and older)

150 mcg

Pregnant women

220 mcg

Breastfeeding women

290 mcg

*Adequate Intake (AI)

Food source

Nutrient content per 100 grams

Seaweed

61,990 mcg*

Iodized salt

10,000 mcg

Cod liver oil

838 mcg

Seafood, fish (depending on type of fish)

36–311 mcg

Seafood, shellfish (depending on type of shellfish)

31–129 mcg

Sea salt

94 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 76–100 mcg of iodine per gram of salt.

Side effects, toxicity, and interactions

Elemental iodine is toxic. This type is found in tincture of iodine. It’s used to disinfect cuts. Swallowing even a small amount can cause death.

Getting too much iodine may also cause problems. It can also cause a goiter. It may also keep your thyroid from working well. This is more likely if you take doses close to 1,000 mcg per day.

Women who are pregnant or breastfeeding shouldn’t take iodine supplements without talking to their healthcare providers. Too much iodine in pregnancy may cause hypothyroidism and a goiter in a newborn.

Talk with your healthcare provider before taking iodine if you take any of these medicines:

  • Lithium

  • Amiodarone

  • Anti-thyroid medicines

  • Medicines for blood pressure, such as angiotensin-converting enzyme (ACE) inhibitors or potassium-sparing diuretics

Online Medical Reviewer: Cynthia Godsey
Online Medical Reviewer: Diane Horowitz MD
Online Medical Reviewer: Rita Sather RN
Date Last Reviewed: 1/1/2019