Figure 10.11 Location of thyroid and parathyroid glands¹

Iodine is found in foods primarily as iodide (I-), some bread dough has iodate (IO3-) added to help with gluten cross-linking². This used to be more commonly used in the past than it is now. Like selenium, iodide concentrations of the soil vary greatly, causing food concentrations to greatly fluctuate. Sea water is high in iodine, thus foods of marine origin, such as seaweed and seafood, are good dietary sources of iodine. Dairy products also tend to be good sources of iodide because it is added to cattle feeds. Cattle receive iodine-containing medications, and iodide-containing sanitizing solutions are used in dairy facilities^3,4.

For most Americans, we consume ample iodine through the consumption of iodized salt. Consumption of 1/2 teaspoon of iodized salt meets the RDA for iodine. There is a global logo for iodized salt. However, I must admit that I don’t recall ever seeing it myself.

The other link below is to a page that contains a scorecard map that depicts access to iodized salt worldwide. It also contains a Youtube video that displays the reduction in iodine deficiency over the last 2 decades.

Salt is iodized with either potassium iodide (KI) or potassium iodate (KIO3). The positives of each are:

Potassium iodide

+ Less expensive

+ Higher iodine content (76% vs. 59% for KIO3)

+ More soluble

Potassium Iodate

+ More stable

The U.S. uses potassium iodide, but the form, and amount, used varies from country-to-country. Most Americans’ salt intake comes from processed foods, many of which are made with non-iodized salt. Iodine is well absorbed (~90%). Some dietary compounds interfere with thyroid hormone production or utilization. These compounds are known as goitrogens5. However, it is not believed that goitrogens are of clinical importance unless there is a coexisting iodine deficiency⁵.

Some examples of foods that contain goitrogens are^3,4,6:

Cassava

Figure 10.12 Cassava plants are typically grown in tropical and subtropical environments⁶

Figure 10.13 The cassava roots are what are typically eaten, but first they must be peeled. These are unprocessed⁷

Figure 10.14 Peeled cassava roots⁸

Millet

Figure 10.15 Millet growing in a field⁹

Figure 10.16 Millets¹⁰

Cruciferous Vegetables (broccoli, cabbage, Brussels sprouts)

Onions

Garlic

Soybeans

Peanuts

Subsections:

10.11 Thyroid Hormone

10.12 Iodine Deficiency & Toxicity

References & Links

1. http://en.wikipedia.org/wiki/File:Illu_thyroid_parathyroid.jpg

2. Gropper SS, Smith JL, Groff JL. (2008) Advanced nutrition and human metabolism. Belmont, CA: Wadsworth Publishing.

3. Byrd-Bredbenner C, Moe G, Beshgetoor D, Berning J. (2009) Wardlaw’s perspectives in nutrition. New York, NY: McGraw-Hill.

4. Whitney E, Rolfes SR. (2008) Understanding nutrition. Belmont, CA: Thomson Wadsworth.

5. Anonymous. (2001) Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. Washington, D.C.: National Academies Press.

6. http://en.wikipedia.org/wiki/File:Casava.jpg

7. http://en.wikipedia.org/wiki/File:Manihot_esculenta_dsc07325.jpg

8. http://en.wikipedia.org/wiki/File:PeeledCassava.jpg

9. https://en.wikipedia.org/wiki/Millet#/media/File:Grain_millet,_early_grain_fill,_Tifton,_7-3-02.jpg

10. https://en.wikipedia.org/wiki/Staple_food#/media/File:Pearl_millet_after_combine_harvesting.jpg

Links

Global Iodized Salt Logo – https://en.wikipedia.org/wiki/File:Global_iodized_salt_logo.jpg

Global Iodine Scorecard – http://www.ign.org/scorecard.htm