Digestion and Absorption of Iodine

Fortified salt is a common source of iodine.

Iodine is a trace mineral that's usually found in the form of iodide. It's needed for your thyroid gland to make thyroid hormones called thyroxine and triiodothyronine. Iodine is also needed for your immune system and might help treat fibrocystic breast disease. It's available in supplemental form, but speak to your doctor before taking iodine supplements.


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Digestion and Absorption

Iodine can be bound to amino acids, or it can be free, usually in the form of iodate or iodide ions. Iodide is the easiest form to absorb, so most of the bound iodine and iodate is converted to iodide by glutathione. The iodide ions are easily absorbed through the walls of the digestive tract in the stomach and small intestine. After it's absorbed, most of it concentrates in the thyroid gland. Some of it also accumulates in the ovaries, skin, and salivary, gastric and mammary glands.


Food Sources

Iodine is found in plant and animal sources of food that are also rich in protein. However, the amount of iodine varies greatly, depending on the amount of iodine in the soil where the plants were grown, or how much iodine was in the animals' feed. Ocean fish, seaweed and seafood contain large amounts of iodine. According to the Office of Dietary Supplements, 90 percent of households in North and South America use iodized salt.


Iodine Deficiency

Iodine deficiency during pregnancy can have a negative impact on fetal growth and development, possibly leading to brain and central nervous system damage. Low intakes of iodine can also cause hypothyroidism and goiter, which is an enlarged thyroid gland in the neck. The Food and Nutrition Board of the Institute of Medicine sets the dietary reference intake for adults at 150 micrograms per day. Women who are pregnant need 220 mcg per day, and women who are breastfeeding need 290 mcg per day.


Supplement Precautions

According to the University of Maryland Medical Center, iodine supplements are used to prevent goiter, help treat fibrocystic breast disease and reduce the risk of thyroid cancer after radiation exposure. Iodine might interact with anti-thyroid drugs, lithium and warfarin. High doses might damage the thyroid gland and increase your risk of thyroid diseases. Speak to your doctor before taking iodine supplements.


Related Reading

Iodine is a trace mineral that is naturally found in the human body and is also derived from food sources such as dairy products, kelp, haddock, cod, perch and sea bass. In the United States, table salt is typically fortified with iodine. Multivitamins and potassium iodide supplements also serve as sources of this mineral. In rare cases, overconsumption of iodine can lead to toxicity.

Tolerable Upper Limit

The recommended daily intake of iodine for adults is 150 micrograms, according to the Linus Pauling Institute at Oregon State University. However, the tolerable upper limit, which represents the maximum safe dosage, is 1,100 micrograms for adults. Most people, except for those in areas such as Northern Japan known for heavy seaweed consumption, consume less than 1,000 micrograms of iodine per day.


Moderate Toxicity

Moderate toxicity is typically marked by elevated levels of thyroid stimulating hormone, or TSH, in the bloodstream. Moderate toxicity, which can occur at levels above the tolerable upper limit, may result in hypothyroidism, or insufficient production of thyroid hormones that regulate metabolism of food nutrients. Consumption of more than 1,700 micrograms of iodine per day may cause goiter, or enlargement of the thyroid gland, according to the Linus Pauling Institute.


Acute Toxicity

Acute toxicity typically occurs at dosages of more than 1 gram of iodine, according to the Linus Pauling Institute. Acute iodine toxicity may cause symptoms such as diarrhea, nausea and vomiting, as well as a burning sensation in the stomach, throat and mouth. Weak pulse and coma are also potential complications of acute toxicity.


Although heavy consumption of iodine may cause toxic symptoms, this mineral serves important functions in the human body when taken in recommended doses. Iodine aids in the metabolism of nutrients for energy, according to the University of Maryland Medical Center. It also supports proper thyroid function and may help prevent cretinism, a type of mental and physical retardation.



Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.

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