Iodine is a trace mineral produced by the body that is essential for normal growth and development. Seventy to eighty percent of iodine is found in the thyroid gland in the neck. The rest is distributed throughout the body, particularly in the ovaries, muscles, and blood. A deficiency of iodine can lead to hypothyroidism (low thyroid hormone levels); symptoms of this condition include sluggishness, weight gain, and sensitivity to temperature changes. In infants and children, hypothyroidism can impair physical and mental development.

The classic sign of iodine deficiency is an enlarged thyroid gland. Some people with hypothyroidism develop an extremely large thyroid, known as goiter. Today, iodine deficiencies in the United States and other developed countries are rare because table salt is supplemented with iodine and crops in developed countries are generally grown in iodine-rich soil. In developing countries, however, where soil is often low in iodine, more than one billion people are estimated to be at risk for disorders caused by iodine deficiencies.

Iodine offers a variety of potential therapeutic uses, primarily in the prevention of hypothyroidism. A health care provider may also recommend iodine supplements for the following conditions:

Fibrocystic Breast Changes
There is some evidence to suggest that hypothyroidism and/or iodine deficiencies may contribute to the development of fibrocystic breast tissue. People with fibrocystic breasts experience tenderness, particularly just before menstruation. Certain foods may worsen breast tenderness such as caffeine (including from chocolate) and high fat foods. During a physical exam, the doctor can feel cysts and fibrous (hardened) tissue. A review of clinical studies found that iodine replacement therapy (particularly for those with low levels of iodine) may improve the tenderness associated with fibrocystic breast tissue. The women taking iodine experienced very few side effects.

Vaginitis
Many women with chronic vaginal symptoms use over-the-counter preparations such as iodine to relieve symptoms. Iodine, used as a douche, may reduce vaginal inflammation as well as the itching and discharge that go along with this health condition. Povidone-iodine has the advantage of iodine without the disadvantages of stinging and staining.

Wounds
Iodine is commonly used as a topical treatment for wounds. Ointments containing iodine are frequently used on burns to lower the risk of infection.

Iodized salt is the primary dietary source of iodine. Plant and animal sea life, such as shellfish, white deep-water fish, and brown seaweed kelp, absorb iodine from the water and are great sources of iodine. Garlic, lima beans, sesame seeds, soybeans, spinach, Swiss chard, summer squash, and turnip greens are also good sources of this mineral. Bakeries may also add iodine to dough as a stabilizing agent, making bread another source of iodine.

There are foods that prevent the body from using iodine such as turnip, cabbage, mustard greens, cassava root, soybeans, peanuts, pinenuts and millet. These foods are called goitrogens and excessive consumption can cause goiters. However, cooking usually inactivates goitrogens.

Sodium iodide (iodine) is available as part of a multivitamin/mineral combination or as a topical treatment for wounds.

The following represent recommended dietary amounts of iodine. In developed countries, these amounts are almost always exceeded through usual dietary intake, which means that supplementation is unnecessary.

Pediatric

• Infants birth to 6 months: 110 mcg (AI)
• Infants 7 to 12 months: 130 mcg (AI)
• Children 1 to 8 years: 90 mcg (RDA)
• Children 9 to 13 years: 120 mcg (RDA)
• Adolescents 14 to 18 years: 150 mcg (RDA)

Adult

• 19 years and older: 150 mcg (RDA)
• Pregnant females: 220 mcg (RDA)
• Breastfeeding females: 290 mcg (RDA)

Therapeutic doses for adults are listed below:

• Douch for vaginitis: generally two tablespoons of an iodine solution to one quart of warm water once per day. Douching should not be done without first consulting your healthcare provider. Similarly, if you are experiencing symptoms of vaginitis (such as vaginal itching and burning), you should be examined by a clinician before douching.
• Wounds or burns: follow your healthcare provider's instructions. Iodine is applied to the surface of the skin to prevent and treat infections associated with wounds and burns.

Because of the potential for side effects and interactions with medications, dietary supplements should be taken only under the supervision of a knowledgeable healthcare provider.

Sudden, large doses of iodine may impair the production of thyroid hormones, causing hypothyroidism temporarily in someone with otherwise normal thyroid function. Excessive iodine intake can also increase the risk for other thyroid diseases such as Hashimoto's, Graves', certain thyroid cancers, and thyrotoxicosis (a dangerous condition due to an excessive amount of thyroid hormones in the bloodstream). For these reasons, iodine supplementation is not recommended for people who live in areas where iodine levels are sufficient.

It may be harmful to take more iodine than is typically consumed per day (160 to 600 micrograms [mcg]) from table salt. Daily intake of 2,000 mcg iodine may be toxic, particularly in people with kidney disease or tuberculosis.

Routine thyroid function tests should be conducted on infants treated with topical iodine.

There are no reports in the scientific literature to suggest that iodine interacts with any conventional medications. However, iodine should be used with caution by people taking thyroid medications.

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