Iodine
Iodine is a trace mineral the body needs to make thyroid hormones, which are essential for normal growth and development. In your body, about 70 to 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. If your body does not have enough iodine, you can develop hypothyroidism (low thyroid hormone levels). Symptoms include sluggishness or fatigue, weight gain, dry skin, and sensitivity to temperature changes. Deficiency happens more often in women than in men, and is more common in pregnant women and older children. In infants and children, hypothyroidism can affect physical and mental development. Premature infants are especially vulnerable to iodine deficiency due to the premature separation from the mom's iodine supply.
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 iodine is added to table salt. Crops in developed countries are generally grown in iodine rich soil, so there is more iodine in food. In developing countries, however, where soil is often low in iodine, more than 1 billion people may be at risk for iodine deficiencies.
Iodine is also used to clean wounds, and iodine tablets can be used to purify water.
Uses
Most people get plenty of iodine. Because of the complex way iodine can affect the thyroid, you should not take iodine supplements unless your doctor tells you to. Iodine may be used for the following conditions:
Oral mucositis (oral inflammation)
Some evidence suggests that an iodine mouth rinse may reduce symptoms of mucositis in the mouth related to chemotherapy or radiation therapy.
Fibrocystic breast changes
Some evidence suggests that iodine may help treat fibrocystic breast disease. Women with fibrocystic breast disease have breast tenderness, particularly just before their periods. 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
Some women with chronic vaginal symptoms use over-the-counter (OTC) iodine douches to reduce vaginal inflammation as well as itching and discharge. Povidone-iodine has the advantage of iodine without the disadvantages of stinging and staining.
Wounds
Iodine is often used to disinfect the skin and clean wounds. Doctors frequently use ointments containing iodine on burns to lower the risk of infection.
Radiation exposure
Potassium iodine can be taken after someone is exposed to radiation to reduce the amount of radioactive iodine that accumulates in the thyroid. This action reduces the risk of thyroid cancer from radiation exposure, but it does not protect against other complications from radiation.
Prevention of goiter
Goiter, or enlargement of the thyroid, can result from iodine deficiency. However, too much iodine can also cause goiter. Goiter due to iodine deficiency is rare in developed countries.
Dietary Sources
Iodized salt is the main source of iodine in the diet. 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 iodine. Bakeries may also add iodine to dough as a stabilizing agent, making bread another source of iodine.
Available Forms
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.
How to Take It
The National Institute of Medicine Adequate Intake (AI) levels are as below:
Infants
- Infants, ages 0 to 6 months: 110 mcg (micrograms) per day
- Infants, ages 7 months to 1 year: 130 mcg per day
RDA (Recommended Dietary Amounts) have been established for children and adults.
Children
- Children, ages 1 to 8 years: 90 mcg per day
- Children, ages 9 to 13 years: 120 mcg per day
- Children, ages 14 to 18 years: 150 mcg per day
Adult
- Ages 18 years and up: 150 mcg per day
- Pregnant females: 220 mcg per day
- Breastfeeding women: 290 mcg per day
The following are Tolerable Uptake Intake Levels (UL), the highest level of daily intake that is not likely to result in side effects:
- Children, 1 to 3 years: 200 mcg per day
- Children, 4 to 8 years: 300 mcg per day
- Children, 9 to 13 years: 600 mcg per day
- From 14 to 18 years (including pregnant and breastfeeding women): 900 mcg day
- For adults, older than 19 (including pregnant and breastfeeding women): 1,100 mcg per day
Wounds or burns: Follow your doctor's instructions. Iodine is applied topically to the skin to prevent and treat infections from wounds and burns.
Precautions
Because of the potential for side effects and interactions with medications, you should take dietary supplements only under the supervision of a knowledgeable health care provider.
High doses of iodine may block the production of thyroid hormones, causing hypothyroidism (low thyroid hormone levels) in someone with otherwise normal thyroid function. Too much iodine can also increase the risk of other thyroid diseases, such as Hashimoto disease, Graves disease, certain thyroid cancers, and thyrotoxicosis (a dangerous condition involving a large amount of thyroid hormones in the bloodstream). For these reasons, you should not take iodine supplements without first talking to your doctor.
Taking more iodine per day than you usually get from table salt, or about 160 to 600 mcg, may be harmful. Daily intake of 2,000 mcg iodine may be toxic, particularly in people with kidney disease or tuberculosis.
Routine thyroid function tests should be done on infants treated with topical iodine.
People with thryoid disease may be particularly susceptible to ill effects of iodine. People with dermatitis herpetiformis can have a worsening of symptoms when taking iodine.
Possible Interactions
If you are being treated with any of the following medications, you should not take iodine without first talking to your health care provider:
Antithyroid drugs: Use of antithyroid drugs, including propylthiouracil (PTU), and iodide may increase the hypothyroid effect of iodides.
Lithium: Use of potassium iodide and lithium (Lithobid) may cause hypothyroidism.
Warfarin: Use of potassium iodide (for hyperthyroidism) with warfarin (Coumadin, a blood-thinning drug) may make warfarin less effective.
High blood pressure medication (ACE inhibitors and angiotensin receptor blockers [ARBs]): Many iodine supplements contain potassium. When used with ACE inhibitors and ARBs, iodine may result in an increased level of potassium in the body, which may be dangerous.
Potassium-sparing diuretics: Since many iodine supplements contain potassium, concurrent use may result in dangerously high levels of potassium.
Amiodorone: Concurrent use with iodine supplements may result in dangerously high levels of iodine.
Supporting Research
Azizi F, Mirmiran P, Hedayati M, et al. Effect of 10 yr of the iodine supplementation on the hearing threshold of iodine deficient schoolchildren. J Endocrinol Invest. 2005 Jul-Aug;28(7):595-8.
Bath SC, Rayman MP. Iodine deficiency in the U.K.: an overlooked cause of impaired neurodevelopment. Proc Nutr Soc. 2013;72(2):226-35.
Boric M, Stanicic J, Dabelic N, Jukic T, Kusic Z. Iodine supplementation in pregnancy. Acta Clin Croat. 2009;48(4):469-73.
de Benoist B, McLean E, Andersson M, Rogers L. Iodine deficiency in 2007: global progress since 2003. Food Nutr Bull. 2008 Sep;29(3):195-202.
Dietary Guidelines for Americans 2005. Rockville, MD: US Dept of Health and Human Services and US Dept of Agriculture; 2005.
Estes NC. Mastodynia due to fibrocystic disease of the breast controlled with thyroid hormone. Am J Surg. Dec 1981;142:764-766.
Galofre JC, Fernandez-Calvet L, Rios M, Garcia-Mayor RV. Increased incidence of thyrotoxicosis after iodine supplementation in an iodine sufficient area. J Endocrinol Invest. 1994;17(1):23-27.
Ghent WR, Eskin BA, Low DA, Hill LP. Iodine replacement in fibrocystic disease of the breast. Can J Surg. Oct 1993;36:453-460.
Gleason. Avery's Diseases of the Newborn. 9th ed. Philadelphia, PA: Elsevier Saunders; 2011.
Gordon RC, Rose MC, Skeaff SA, Gray AR, Morgan KM, Ruffman T. Iodine supplementation improves cognition in mildly iodine-deficient children. Am J Clin Nutr. 2009;90(5):1264-71.
Grio R, Zaccheo F, Mazza D, et al. Effectiveness of povidone-iodine in the treatment of non-specific vaginitis. Minerva Ginecol. [Italian.] 1990;42(4):129-131.
Harihara Y, Konishi T, Kobayashi H, et al. Effects of applying povidone-iodine just before skin closure. Dermatology. 2006;212 Suppl 1:53-7.
Henzen C, et al. Iodine-induced hyperthyroidism (iodine-induced Basedow's disease): a current disease picture. Schweiz Med Wochenschr. May 1, 1999;129(17):658-664.
Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press; 2001.
Jun JY, Manni A. Medical management of persistent or recurrent differentiated thyroid carcinoma. Otolaryngol Clin North Am. 2008 Dec;41(6):1241-60, xi-xii. Review.
Koutras DA. Control of efficiency and results, and adverse effects of excess iodine administration on thyroid function. Ann Endocrinol (Paris). 1996;57(6):463-469.
Kronenberg. Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Elsevier Saunders; 2008.
Leung A, Braverman L, He X, Heeren T, Pearce E. Breastmilk iodine concentrations following acute dietary iodine intake. Thyroid. 2012;22(11):1176-80.
Leung A, Pearce E, Braverman L. Iodine Nutrition in Pregnancy and Lactation. Endocrinology and Metabolism Clinics . 2011;40(4).
Liu P, Liu SJ, Su XH, Zhang SB, Ji XH. An updated systematic review and commentary examining the effectiveness of radioactive iodine remnant ablation in well-differentiated thyroid cancer. Endocrinology and Metabolism Clinics. 2008;37(2).
Martin JC, Savige GS, Mitchell EK. Health knowledge and iodine intake in pregnancy. Aust N Z J Obsetet Gynaecol. 2014;54(4):312-6.
Melmed. Williams Textbook of Endocrinology. 12th ed. Philadelphia, PA: Elsevier Saunders; 2011.
Minelli R, et al. Effects of excess iodine administration on thyroid function in euthyroid patients with a previous episode of thyroid dysfunction induced by interferon-alpha treatment. Clin Endocrinol (Oxf). Sep, 1997;47(3):357-361.
Nyirjesy P, Weitz MV, Grody MH, Lorber B. Over-the-counter and alternative medicines in the treatment of chronic vaginal symptoms. Obstet Gynecol. 1997;90(1):50-53.
Schlienger JL, et al. Iodine and thyroid function. Rev Med Interne. 1997;18(9):709-716.
Teas J, Pino S, Critchley A, Braverman LE. Variability of iodine content in common commercially available edible seaweeds. Thyroid. 2004;14(10):836-41.
van de Ven AC, Neea-Maier RT; Ross HA, et al. Longitudinal trends in thyroid function in relation to iodine intake: ongoing changes of thyroid function despite adequate current iodine status. Eur J Endocrinol. 2014;170(1):49-54.
Yu H, Tak-Yin M. The efficacy of povidone-iodine pessaries in a short, low-dose treatment regime on candidal, trichomonal and non-specific vaginitis. Postgrad Med J. 1993;69 (Suppl 3):S58-S61.
Zhou SJ, Anderson AJ, Gibson RA, Makrides M. Effect of iodine supplementation in pregnancy on child development and other clinical outcomes: a systematic review of randomized controlled trials. Am J Clin Nutr. 2013;98(5):1241-54.
Zimmermann MB, Jooste PL, Pandav CS. Iodine-deficiency disorders. Lancet. 2008 Oct 4;372(9645):1251-62.