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Your body needs iodine, a mineral, to work properly. The thyroid gland, for example, uses iodine to make the thyroid hormone thyroxin. Most iodine is in the form of iodide. These terms are often used interchangeably.

Iodide helps to:
  • Regulate metabolic rate
  • Regulate growth and development
  • Promotes bone and protein synthesis

Recommended Intake
Age group Recommended Dietary Allowance [RDA] or Adaquate Intake (micrograms/day) Upper Limits [UL] (micrograms/day) 0-6 months110Not determinable7-12 months130Not determinable1-3 years902004-8 years903009-13 years12060014-18 years15090019 years and older1501,100Pregnancy (18 or younger)220900Pregnancy (19-50 years)2201,100Lactation (18 or younger)290900Lactation (19-50 years)2901,100
Too Little Iodide
Iodine deficiency can cause a range of problems, including mental retardation, hypothyroidism, goiter, and other growth and developmental problems. Thyroid enlargement (goiter) is one of the early signs of iodine deficiency. Not getting enough iodine is especially harmful for the developing brain, such as during pregnancy and in infants. This is why the American Thyroid Association recommends that pregnant and breastfeeding women take a daily prenatal supplement that contains iodine.

Because we have iodized salt in the US, goiter is rarely seen. If eaten in large quantities, some foods, like raw turnips and rutabagas, have chemicals that can cause goiters and inhibit thyroid gland functions. These chemicals, called goitrogens, are destroyed when the foods are cooked, so problems are uncommon.

Too Much Iodide
The thyroid can also become enlarged if you have too much iodide in your diet, though this is rare in the US. This “toxic goiter” is caused by elevated concentrations of thyroid stimulating hormone (TSH). This is often seen in people who eat a lot of seaweed, which can add a significant amount of iodide to the diet. Iodide levels up to 1 milligram (more than six times the RDA) appear to be safe.

Health Implications
When the thyroid gland releases fewer hormones than the body needs, the result is hypothyroidism. Some of the symptoms include:

When more hormones are released than necessary, the result is hyperthyroidism . Some symptoms include:
  • Heat intolerance
  • Tremors
  • Enlarged thyroid gland (goiter)
  • Heart palpitations
  • Increased sweating
  • Nervousness, irritability
  • Redness, swelling, and protrusion of the eyes
  • Shortness of breath
  • Increased number of bowel movements
  • Irregular or no menstrual period

A low iodide intake can especially impact children, causing a condition called cretinism . If not treated, the condition can lead to intellectual disability and abnormal growth. Iodine supplements can help reverse some of the affects. People who have a low iodide intake may be at risk of getting thyroid cancer, although it is not known exactly what causes the disease.

Major Food Sources
Iodide is found naturally in food grown in or near coastal seas. Seafood is naturally high in iodide, as are plants grown near the sea. Molasses and iodized salt are also good sources. Most people get plenty of iodide from the iodized salt in their diets, since only ½ teaspoon of iodized salt provides enough iodide to reach an adult's RDA for the day. The sea salt found in health food stores is generally not a good source because iodide is lost during processing.

FoodServing Size Iodide content (micrograms) Table salt, iodized¼ teaspoon100Cod, cooked3 ounces87Potato, cooked1 medium7Spinach, cooked½ cup5Almonds1 ounce4
Tips for Increasing Your Iodide Intake
In general, there is little need to increase your iodide intake. Most people in the US get plenty from their diets, much of this coming from iodized salt. But if you use sea salt (or another type of salt) that does not have iodide, you can get the mineral from seafood or other sources. This is also true if you are on a low-sodium diet. Talk to your doctor if you are concerned about how much iodide you are getting.

American Dietetic Association

American Thyroid Association

Dietitians of Canada

The Thyroid Foundation of Canada

What are the risk factors for thyroid cancer? American Cancer Society website. Available at: Updated January 20, 2012. Accessed July 12, 2012.

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Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc . Institute of Medicine website. Available at: .

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Institute of Medicine. Dietary reference intakes: elements. Institute of Medicine website. Available at: Accessed July 12, 2012.

Iodine. EBSCO Natural and Alternative Treatments website. Available at: Updated August 2011. Accessed July 12, 2012.

Iodine. Oregon State University Linus Pauling Institute website. Available at: Updated March 2010. Accessed July 19, 2012.

Pennington JAT. Bowes & Church’s Food Values of Portions Commonly Used. Philadelphia, PA: Lippincott-Raven Publishers; 1998

Scheinberg D. Congenital hypothyroidism. EBSCO Health Library website. Available at: . Updated September 2011. Accessed July 12, 2012.

The Vitamin Foundation. Iodine deficiency. The Vitamin Foundation website. Available at: Accessed July 12, 2012.

Last Reviewed July 2012

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