• Iodine

    Iodized salt image 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.

    Functions

    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 months 110 Not determinable
    7-12 months 130 Not determinable
    1-3 years 90 200
    4-8 years 90 300
    9-13 years 120 600
    14-18 years 150 900
    19 years and older 150 1,100
    Pregnancy (18 or younger) 220 900
    Pregnancy (19-50 years) 220 1,100
    Lactation (18 or younger) 290 900
    Lactation (19-50 years) 290 1,100

    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.
    Food Serving Size Iodide content
    (micrograms)
    Table salt, iodized ¼ teaspoon 100
    Cod, cooked 3 ounces 87
    Potato, cooked 1 medium 7
    Spinach, cooked ½ cup 5
    Almonds 1 ounce 4

    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.

    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

    What are the risk factors for thyroid cancer? American Cancer Society website. Available at: http://www.cancer.org/Cancer/ThyroidCancer/DetailedGuide/thyroid-cancer-risk-factors. Updated January 20, 2012. Accessed July 12, 2012.

    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.

    Institute of Medicine. Dietary reference intakes: elements. Institute of Medicine website. Available at: http://www.iom.edu/~/media/Files/Activity%20Files/Nutrition/DRIs/DRI%5FElements.ashx. Accessed July 12, 2012.

    Iodine. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/healthLibrary/. Updated August 2011. Accessed July 12, 2012.

    Iodine. Oregon State University Linus Pauling Institute website. Available at: http://lpi.oregonstate.edu/infocenter/minerals/iodine/. 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: http://www.ebscohost.com/healthLibrary/ . Updated September 2011. Accessed July 12, 2012.

    The Vitamin Foundation. Iodine deficiency. The Vitamin Foundation website. Available at: http://www.vitamincfoundation.org/iodine.htm. Accessed July 12, 2012.

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