IODINE AND HEALTH

 

What is iodine deficiency?
Iodine is an element that is needed for the production of thyroid hormone. The body does not make iodine, so it is an essential part of your diet. Iodine is found in various foods (see Table 1 below). If you do not have enough iodine in your body, you cannot make enough thyroid hormone. Thus, iodine deficiency can lead to enlargement of the thyroid (goiter – see Goiter brochure), hypothyroidism (see Hypothyroidism brochure) and to mental retardation in infants and children whose mothers were iodine deficient during pregnancy.

Before the 1920s, iodine deficiency was common in the Great Lakes, Appalachian, and Northwestern U.S. regions and in most of Canada. Treatment of iodine deficiency by the introduction of iodized salt has virtually eliminated the “goiter belt” in these areas. However, many other parts of the world do not have enough iodine available through their diet and iodine deficiency continues to be an important public health problem globally. Approximately 40% of the world’s population remains at risk for iodine deficiency.

ADDITIONAL PATIENT RESOURCES

SYMPTOMSWhat are the symptoms of iodine deficiency?
All of the symptoms of iodine deficiency are related to its effect on the thyroid:

Goiter - Without adequate iodine, the thyroid progressively enlarges (develops a goiter) as it tries to keep up with demand for thyroid hormone production. Worldwide, iodine deficiency is the most common cause of thyroid enlargement and goiter (see Goiter brochure). Within a goiter, nodules can develop. Patients with a large goiter may experience symptoms of choking, especially when lying down, and difficulty swallowing and breathing.

Hypothyroidism – As the body’s iodine levels fall, hypothyroidism may develop, since iodine is essential for making thyroid hormone. While this is uncommon in the United States, iodine deficiency is the most common cause of hypothyroidism worldwide (see Hypothyroidism brochure).

Pregnancy-related problems - Iodine deficiency is especially important in women who are pregnant or nursing their infants. Severe iodine deficiency in the mother has been associated with miscarriages, stillbirth, preterm delivery, and congenital abnormalities in their babies. Children of mothers with severe iodine deficiency during pregnancy can have mental retardation and problems with growth, hearing, and speech. In the most severe form, an underactive thyroid can result in cretinism (a syndrome characterized by permanent brain damage, mental retardation, deaf mutism, spasticity, and short stature), though this is not seen in the United States. Congenital hypothyroidism due to iodine deficiency is the most common preventable cause of mental retardation in the world. Even mild iodine deficiency during pregnancy, which may be present in some women in the United States, may be associated with low intelligence in children.

CAUSES

What are the causes of iodine iodine deficiency?
Since the body does not make iodine, it relies on the diet to have enough iodine. Thus, iodine deficiency is caused but not having enough iodine in the diet. Iodine is present naturally in soil and seawater. The availability of iodine in foods differs in various regions of the world (see Table 1). Individuals in the United States can maintain adequate iodine in their diet by using iodized table salt (unless they have to restrict the amount of salt in their diet), by eating foods high in iodine, particularly dairy products, seafood, meat, some breads, and eggs, and by taking a multivitamin containing iodine (see below). However, the amount of iodine in foods is not listed on food packaging in the U.S., and it can be difficult to identify sources of iodine in foods.

Table 1. Common Sources of Dietary Iodine
Breads Iodized table salt
Cheese Saltwater fish
Cow’s milk Seaweed (including kelp, dulce, nori)
Eggs Shellfish
Frozen yogurt Soy milk
Ice cream Soy sauce
Iodine-containing multivitamins Yogurt

 

Table 2. Median Population Urinary Iodine Values and Iodine Nutrition
MEDIAN URINARY IODINE CONCENTRATION (μg/L)
CORRESPONDING IODINE INTAKE (μg/day)
IODINE NUTRITION
<20
<30
Severe deficiency
20-49
30-74
Moderate deficiency
50-99
75-149
Mild deficiency
100-199
150-299
Optimal
200-299
300-449
More than adequate
>299
>449
Possible excess

[From WHO, UNICEF and ICCIDD 2001 Assessment of the Iodine Deficiency Disorders and monitoring their elimination. A guide for programme managers. WHO publ., Geneva. WHO/NHD/01.1]

DIAGNOSIS

How do you diagnose iodine deficiency?
Iodine deficiency is diagnosed across populations and not specifically in individuals. Since iodine is released from the body through the urine, the best way to determine iodine deficiency across a large population is to measure the amounts of iodine in urine samples. Iodine deficiency is defined as a median urinary iodine concentration less than 50 μg/L in a population (see Table 2).

In the United States, iodine status has remained generally adequate in the last 2 decades although studies have shown that urinary iodine levels dropped by about half between the early 1970s and the early 1990s. However, iodine deficiency is a major issue in other parts of the world, including parts of Europe, Africa and Asia.

TREATMENT

How is iodine deficiency treated?
There are no tests to confirm if you have enough iodine in your body. When iodine deficiency is seen in an entire population, it is best managed by ensuring that common foods that people eat contain sufficient levels of iodine. Since even mild deficiency during pregnancy can have effects on delivery and the developing baby, all pregnant and breastfeeding women should take a multivitamin containing at least 150 μg iodine per day.

How is iodine deficiency prevented?
As with many diseases, it is better to prevent the problem rather than have to treat it. Over the last 80 years, world-wide efforts have been made to eliminate iodine deficiency. Indeed, elimination of iodine deficiency has been a major goal of the World Health Organization. Iodized salt has been the mainstay of treatment for iodine deficiency worldwide, including in the United States. Injections of iodized oil are occasionally used in regions of the world where widespread iodized salt use is not possible. Iodination of water supplies also has been effective in some places.

United States Recommendations - The Institute of Medicine has set the Recommended Dietary Allowance (RDA) for iodine in adult men and women at 150 μg per day. Individuals who add table salt to their food regularly should use iodized salt. One teaspoon of iodized salt contains approximately 400 μg iodine. Most iodine-containing multivitamins have at least 150 μg iodine, but only about half of the types of multivitamins in the U.S. contain iodine.

The RDA is 220 μg iodine per day for pregnant women and 290 μg iodine per day for breastfeeding women. Because the effects of iodine deficiency are most severe in pregnant women and their babies, the American Thyroid Association has recommended that all pregnant and breastfeeding women in the U.S. and Canada take a prenatal multivitamin containing 150 μg iodine per day.

Are there problems with taking too much iodine?
Taking too much iodine can also cause problems. This is especially true in individuals that already have thyroid problems, such as nodules, hyperthyroidism and autoimmune thyroid disease. Administration of large amounts of iodine through medications (ie Amiodarone), radiology procedures (iodinated intravenous dye) and dietary excess (Dulce, kelp) can cause or worsen hyperthyroidism and hypothyroidism.

In addition, individuals who move from an iodine-deficient region (for example, parts of Europe) to a region with adequate iodine intake (for example, the United States) may also develop thyroid problems since their thyroids have become very good at taking up and using small amounts of iodine. In particular, these patients may develop iodine-induced hyperthyroidism

 american thyroid association website  www.thyroid.org   2011

Iodine

 

FROM MEDLINE PLUS  - 2011

 

What is it?

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 US 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 US, iodized salt is not required, but it is widely available. Researchers estimate that iodized salt is used regularly by about half the US 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 for radiation emergencies, to protect the thyroid gland against radioactive iodides. Potassium iodide tablets for use in a radiation emergency are available as FDA-approved products (ThyroShield, Iosat) 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.

How effective is it?

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:

Likely effective for…

  • Iodine deficiency. Taking iodine supplements is effective for preventing and treating iodine deficiencies including goiter.
  • Radiation exposure. Iodine taken by mouth is effective for protecting against exposure to radioactive iodides in a radiation emergency.
  • Thyroid conditions. Taking iodine orally can improve thyroid storm and hyperthyroidism.

Possibly effective for…

  • Painful fibrous breast tissue (fibrocystic breast disease), when taken by mouth.
  • Preventing soreness and swelling inside the mouth, caused by chemotherapy treatments for cancer, when applied directly to the affected area.
  • Foot ulcers associated with diabetes, when applied directly to the affected area.

Insufficient evidence to rate effectiveness for…

  • Treating a skin condition caused by a fungus (Cutaneous sporotrichosis).

How does it work?

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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.

Are there safety concerns?

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Iodine is LIKELY SAFE for most people when taken by mouth at recommended amounts.

Iodine can cause significant side effects in some people. Common side effects include nausea and stomach pain, runny nose, headache, metallic taste, and diarrhea.

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 of iodine 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: People with autoimmune thyroid disease may be especially sensitive to the harmful side effects of iodine.

Rash called dermatitis herpetiformis: Taking iodine can cause worsening of this rash.

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.

Are there interactions with medications?

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Major

Do not take this combination.
Medications for an overactive thyroid (Antithyroid drugs)
Iodine can affect the thyroid. Taking iodine along with medications for an overactive thyroid might decrease the thyroid too much. Do not take iodine supplements if you are taking medications for an overactive thyroid.

Some of these medications include methenamine mandelate (Methimazole), methimazole (Tapazole), potassium iodide (Thyro-Block), and others.

Moderate

Be cautious with this combination.
Amiodarone (Cordarone)
Amiodarone (Cordarone) contains iodine. Taking iodine supplements along with amiodarone (Cordarone) might cause too much iodine in the blood. Too much iodine in the blood can cause side effects that affect the thyroid.
Lithium
Large amounts of iodine can decrease thyroid function. Lithium can increase iodine’s effects on the thyroid. Taking iodine along with lithium might decrease the thyroid function too much. Do not take large amounts of iodine if you are taking lithium.
Medications for high blood pressure (ACE inhibitors)
Some medications for high blood pressure might decrease how quickly the body gets rid of potassium. Most iodide supplements contain potassium. Taking potassium iodide along with some medications for high blood pressure might cause too much potassium in the body. Do not take potassium iodide if you are taking medications for high blood pressure.

Some medications for high blood pressure include captopril (Capoten), enalapril (Vasotec), lisinopril (Prinivil, Zestril), ramipril (Altace), and others.

Medications for high blood pressure (Angiotensin receptor blockers (ARBs))
Some medications for high blood pressure might decrease how quickly the body gets rid of potassium. Most iodine supplements contain potassium. Taking potassium iodide along with some medications for high blood pressure might cause too much potassium in the body. Do not take potassium iodide if you are taking medications for high blood pressure.

The ARBs include losartan (Cozaar), valsartan (Diovan), irbesartan (Avapro), candesartan (Atacand), telmisartan (Micardis), and eprosartan (Teveten).

Water pills (Potassium-sparing diuretics)
Most iodine supplements contain potassium. Some “water pills” might also increase potassium in the body. Taking potassium iodide along with some “water pills” might cause too much potassium to be in the body. Do not take potassium iodide if you are taking “water pills” that increase potassium in the body.

Some “water pills” that increase potassium in the body include spironolactone (Aldactone), triamterene (Dyrenium), and amiloride (Midamor).

Are there interactions with herbs and supplements?

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There are no known interactions with herbs and supplements.

Are there interactions with foods?

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There are no known interactions with foods.

What dose is used?

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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.

Other names

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Atomic number 53, Cadexomer Iodine, Diatomic Iodine, I2, Iode, Iodide, Iodized Salt, KI, Lugol’s Solution, Molecular Iodine, Monoatomic Iodine, Potassium Iodide, Povidone Iodine, Saturated Solution Potassium Iodide, Sodium Iodide, Sodium Iodine, Sodium Periodate, SSKI, Yodo.

Methodology

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To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.

References

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  1. PL Detail-Document: Potassium iodide: frequently asked questions. Pharmacist’s Letter/Prescriber’s Letter. March, 2011.
  2. PL Detail-Document: Potassium iodide for thyroid protection against nuclear radiation. Pharmacist’s Letter/Prescriber’s Letter. March, 2011.
  3. Sterling JB, Heymann WR. Potassium iodide in dermatology: a 19th century drug for the 21st century-uses, pharmacology, adverse effects, and contraindications. J Am Acad Dermatol 2000;43:691-7.
  4. Cuadros RG, Vidotto V, Bruatto M. Sporotrichosis in the metropolitan area of Cusco, Peru, and in its region. Mycoses 1990;33:231-40.
  5. Houh W, Chung SR, Ro BI. Itraconazole in the treatment of sporotrichosis: a Korean experience. Trop Doct 1995;25:107-9.
  6. Arora U, Aggarwal A, Arora RK. Sporotrichosis in Amritsar–a case report. Indian J Pathol Microbio 2003;46:442-3.
  7. Shinogi T, Misago N, Narisawa Y. Cutaneous sporotrichosis with refractory and reinfectious lesions in a healthy female. J Dermatol 2004;31:492-6.
  8. Mahajan VK, Sharma NL, Sharma RC, et al. Cutaneous sporotrichosis in Himachal Pradesh, India. Mycoses 2005;48:25-31.
  9. Bonifaz A, Saúl A, Paredes-Solis V, et al. Sporotrichosis in childhood: clinical and therapeutic experience in 25 patients. Pediatr Dermatol 2007;24:369-72.
  10. Agarwal S, Gopal K, Umesh, Kumar B. Sporotrichosis in Uttarakhand (India): a report of nine cases. Int J Dermatol 2008;47:367-71.
Last reviewed – 04/02/2011

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