Iodine is a trace mineral produced by the body that is essential for normal growth and development. Approximately 70 - 80% 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 or fatigue, weight gain, dry skin, 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 1 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:

Expectorant

Iodine is used as an expectorant, which gets rid of excess phlegm (mucus) from the throat and airways. It is commonly used in many cough syrups, called antitussives, which quiets coughs.

Fibrocystic breast changes and breast cancer

Some evidence suggests that hypothyroidism and 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.

Laboratory studies have found that iodine or iodine-rich seaweed inhibits breast tumor development. There is a relatively low rate of breast cancer in Japanese women who consume a diet containing iodine-rich seaweed. However, more clinical research should be performed to determine if iodine decreases the chances of developing breast cancer.

Vaginitis

Many women with chronic vaginal symptoms use over-the-counter (OTC) 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.

Others

Iodine as radioactive iodine is used in the treatment of overactivity of the thyroid gland, also known as hyperthyroidism. Radioactive iodine from is quickly absorbed through the lungs and accumulates in the thyroid gland. A large dose of iodine (as potassium iodide) blocks the uptake of the radioactive iodine, decreasing the damage to the thyroid gland in cases of accidental radioactivity exposure.

There is also limited clinical research that suggests that iodine mouth rinses may decrease the severity of mucositis (oral inflammation) in the mouth related to cancer chemotherapy or radiation therapy.

Auditory disturbances may be present in iodine deficient children. Several clinical studies support the use of iodine supplementation in children with hearing problems.

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, pine nuts, 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. Iodine can also be found in dietary supplements containing seaweeds such as kelp and bladderwrack.

The Food and Nutrition Board of the U.S. National Academy of Sciences has recommended the following daily dietary intakes of iodine (iodide):

Pediatric

For infants ages 0 – 6 months: The recommended daily amount of iodine is 40 mcg (micrograms).

For infants ages 6 months to 1 year: The recommended daily amount of iodine is 50 mcg.

For children ages 1 – 10 years: The recommended daily amount of iodine is 70 - 120 mcg.

For children ages 10 - 18 years: The recommended daily amount of iodine is 120 – 150 mcg.

Adult

For adults ages 18 years and up: The recommended daily amount of iodine is 120 - 150 mcg.

For pregnant females: The recommended daily amount of iodine is 175 mcg.

For lactating and breast-feeding females: The recommended daily amount of iodine is 200 mcg.

Douch for vaginitis: Generally, two tablespoons of an iodine solution to one quart of warm water is used, douching with the full amount once per day. Douching should not be done without first consulting your health care provider. Similarly, if you are experiencing symptoms of vaginitis (such as vaginal itching and burning), you should be examined by a doctor before douching.

Wounds or burns: Follow your health care 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 health care provider.

Sudden, large doses of iodine may impair the production of thyroid hormones, causing hypothyroidism (low thyroid hormone levels) temporarily in someone with otherwise normal thyroid function. Excessive iodine intake can also increase the risk for other thyroid diseases, such as Hashimoto's disease, Graves' disease, 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, or 160 - 600 mcg (micrograms) 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.

If you are currently being treated with any of the following medications, you should not use iodine supplements without first talking to your health care provider:

Antithyroid Drugs -- Use of antithyroid drugs, including propylthiouracil (PTU), and iodide may potentiate the hypothyroid effect of iodides.

Lithium -- Use of potassium iodide and lithium (Lithobid®) may result in hypothyroidism.

Warfarin -- Use of potassium iodide (for hyperthyroidism) and warfarin (Coumadin®, a blood thinning drug) may decrease the anticoagulant effectiveness of warfarin.

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