Iodide
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Iodide

Iodized salt image Iodide is an essential trace mineral. It is a component of the thyroid hormone thyroxin, which regulates the rate at which your body uses energy. Many people confuse this mineral with iodine, the elemental form that is actually poisonous to humans.

Functions

Iodide is a component of thyroxin, a thyroid hormone that helps to:

  • Regulate metabolic rate
  • Regulate growth and development
  • Promotes bone and protein synthesis

Recommended Intake

Age group Recommended Dietary Allowance [RDA]
(micrograms/day)
Upper Limits [UL]
(micrograms/day)
0-6 months110Not determinable
7-12 months130Not determinable
1-3 years90200
4-8 years90300
9-13 years120600
14-18 years120900
19 years and older1201,100
Pregnancy (18 or younger) 220900
Pregnancy (older than 18) 2201,100
Lactation (18 or younger)290900
Lactation (older than 18) 2901,100

Too Little Iodide

If you don’t have enough iodide, your body can’t make enough thyroxin. This slows down the rate at which the body burns energy, so weight gain can become a problem. This lack of iodide can cause a goiter, or enlarged thyroid gland. This happens when the thyroid gland grows to try and take up more iodide from the bloodstream. A chronic iodide deficiency can result in destruction of the thyroid gland.

Because we have iodized salt in the United States, 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 United States. 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.

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 teaspoon100
Cod, cooked3 ounces87
Potato, cooked1 medium7
Spinach, cooked½ cup5
Almonds1 ounce4

Health Implications

When the thyroid gland releases fewer hormones than the body needs, the result is hypothyroidism—the most common form of thyroid dysfunction. 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 mental retardation and abnormal growth. Iodine supplements can reverse some of the affects. People who have a low iodide intake are also at an increased risk of getting thyroid cancer, although it is not known exactly what causes the disease.

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 doesn't 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.

RESOURCES:

American Dietetic Association
http://www.eatright.org/

American Thyroid Association
http://www.thyroid.org/

CANADIAN RESOURCES:

Dietitians of Canada
http://www.dietitians.ca/

The Thyroid Foundation of Canada
http://www.thyroid.ca/

References

Duyff RL. The American Dietetic Association’s Complete Food and Nutrition Guide . Minneapolis, MN: Chronimed Publishing; 1998.

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: http://www.iom.edu/CMS/3788.aspx.

Garrison R, Somer E. The Nutrition Desk Reference. New Canaan, CT: Keats Publishing; 1995.

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: http://www.ebscohost.com/thisTopic.php?marketID=15topicID=81. Updated January 2008. Accessed July 18, 2008.



Last reviewed June 2008 by Dianne Scheinberg, MS, RD, LDN

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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