Iodine is a chemical element. The body needs iodine but cannot make it. The needed iodine must come from the diet. As a rule, there is very little iodine in food, unless it has been added during processing, which is now the case with salt. Most of the world’s iodine is found in the ocean, where it is concentrated by sea life, especially seaweed.

The thyroid gland needs iodine to make hormones. If the thyroid doesn’t have enough iodine to do its job, feedback systems in the body cause the thyroid to work harder. This can cause an enlarged thyroid gland (goiter), which becomes evident as a swollen neck.

Other consequences of not having enough iodine (iodine deficiency) are also serious. Iodine deficiency and the resulting low levels of thyroid hormone can cause women to stop ovulating, leading to infertility. Iodine deficiency can also lead to an autoimmune disease of the thyroid and may increase the risk of getting thyroid cancer. Some researchers think that iodine deficiency might also increase the risk of other cancers such as prostate, breast, endometrial, and ovarian cancer.

Iodine deficiency during pregnancy is serious for both the mother and the baby. It can lead to high blood pressure during pregnancy for the mother, and mental retardation for the baby. Iodine plays an important role in development of the central nervous system. In extreme cases, iodine deficiency can lead to cretinism, a disorder that involves severely stunted physical and mental growth.

Iodine deficiency is a common world health problem. The most recognized form of deficiency is goiter. Additionally, across the globe iodine deficiency is thought to be the most common preventable cause of mental retardation. Early in the twentieth century, iodine deficiency was common in the U.S. and Canada, but the addition of iodine to salt has improved public health. The addition of iodine to salt is required in Canada. In the U.S., iodized salt is not required, but it is widely available. Researchers estimate that iodized salt is used regularly by about half the U.S. population.

Iodine is used to prevent iodine deficiency and its consequences, including goiter. It is also used for treating a skin disease caused by a fungus (cutaneous sporotrichosis); treating fibrocystic breast disease; preventing breast cancer, eye disease, diabetes, and heart disease and stroke; and as an expectorant.

Iodine is also used to treat radiation emergency caused by exposure to radioactive iodides. Potassium iodide tablets for use in a radiation emergency are available as FDA-approved products (Thyro-Block, Iostat) and on the Internet as food supplements. Potassium iodide should only be used in a radiation emergency, not in advance of an emergency to prevent sickness.

Iodine is applied to the skin to kill germs, prevent soreness inside the mouth (mucositis) caused by chemotherapy, and treat diabetic ulcers.

Iodine is also used for water purification.

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

The effectiveness ratings for IODINE are as follows:

Iodine reduces thyroid hormone and can kill fungus, bacteria, and other microorganisms such as amoebas. A specific kind of iodine called potassium iodide is also used to treat (but not prevent) the effects of a radioactive accident.

Iodine is LIKELY SAFE for most people when taken by mouth at recommended amounts. However, in sensitive people, iodine can cause side effects including swelling of the lips and face (angioedema), severe bleeding and bruising, fever, joint pain, lymph node enlargement, allergic reactions including hives, and death.

Large amounts or long-term use are POSSIBLY UNSAFE. Adults should avoid prolonged use of doses higher than 1100 mcg per day (the upper tolerable limit, UL) without proper medical supervision. In children, doses should not exceed 200 mcg per day for children 1 to 3 years old, 300 mcg per day for children 4 to 8 years old, 600 mcg per day for children 9 to 13 years old, and 900 mcg per day for adolescents. These are the upper tolerable limits (UL).

In both children and adults, there is concern that higher intake can increase the risk of side effects such as thyroid problems. Iodine in larger amounts can cause metallic taste, soreness of teeth and gums, burning in mouth and throat, increased saliva, throat inflammation, stomach upset, diarrhea, wasting, depression, skin problems, and many other side effects.

When iodine is used directly on the skin, it can cause skin irritation, stains, allergic reactions, and other side effects. Be careful not to bandage or tightly cover areas that have been treated with iodine to avoid iodine burn.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Iodine is LIKELY SAFE when taken by mouth in recommended amounts. Do not take more than 1100 mcg of iodine per day if you are over 18 years old; do not take more than 900 mcg of iodine per day if you are 14 to 18 years old. Higher intake might cause thyroid problems. The topical product (2% solution) is LIKELY SAFE for use on the skin.

Autoimmune thyroid disease (AITD): People with AITD may be especially sensitive to the harmful side effects of iodine.

Thyroid disorders, such as too little thyroid function (hypothyroidism), an enlarged thyroid gland (goiter), or a thyroid tumor: Prolonged use or high doses of iodine might make these conditions worse.

Major

Moderate

There are no known interactions with herbs and supplements.

There are no known interactions with foods.

The following doses have been studied in scientific research:

BY MOUTH:

• For radiation emergencies: potassium iodide (KI) should be taken just prior to, or as soon as possible after, exposure. Radiation is most harmful to pregnant or breastfeeding women and children, so KI is dosed according to amount of radiation exposure and age. Radiation exposure is measured in centigrays (cGy). For infants, babies, children, adolescents, and pregnant or breastfeeding women, KI is given if radiation exposure is 5 centigrays (cGy) or more. Tablets can be crushed and mixed with fruit juice, jam, milk, etc.
  • For birth through 1 month, the dose is 16 mg of KI;
  • For babies and children over 1 month through 3 years, 32 mg;
  • For children 3 to 12 years, 65 mg;
  • For adolescents 12 through 18 years, 65 mg or 120 mg if the adolescent is approaching adult size;
  • For pregnant or breastfeeding women, 120 mg.
  • For adults 18 to 40 years with exposure to 10 cGy or more, 130 mg of KI is given.
  • For adults over 40 years with exposure to 500 cGy or more, 130 mg of KI is given.

The National Institute of Medicine has set Adequate Intake (AI) of iodine for infants: 0 to 6 months, 110 mcg/day; 7 to 12 months, 130 mcg/day.

For children and adults, Recommended Dietary Amounts (RDA) have been set: children 1 to 8 years, 90 mcg/day; 9 to 13 years, 120 mcg/day; people age 14 and older, 150 mcg/day. For pregnant women, the RDA is 209 mcg/day, and breastfeeding women, 290 mcg/day.

Tolerable Upper Intake Levels (UL), the highest level of intake that is not likely to cause unwanted side effects, for iodine intake have been set: children 1 to 3 years, 200 mcg/day; 4 to 8 years, 300 mcg/day; 9 to 13 years, 600 mcg/day; 14 to 18 years (including pregnancy and breastfeeding), 900 mcg/day. For adults older than age 19 including pregnant and breastfeeding women, the Tolerable Upper Intake Level is 1100 mcg/day.

Atomic number 53, Potassium Iodide, Povidone Iodine, I.

To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.methodology (http://www.nlm.nih.gov/medlineplus/druginfo/natural/methodology.html).

To see all references for the Iodine page, please go to http://www.nlm.nih.gov/medlineplus/druginfo/natural/35.html.

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Page last updated: 30 September 2010