People who do not use iodized salt The use of iodized salt is the most widely used strategy to control iodine deficiency. Surveys indicate that many pregnant women in the United States might consume insufficient amounts of iodine even if they do not have signs or symptoms of overt iodine deficiency [ 35 ]. The impact, if any, of this insufficient intake on fetal development is not known. Vegans and people who eat few or no dairy products, seafood, and eggs Seafood, eggs, milk, and milk products are among the best sources of iodine.
Vegans, people with certain food allergies or lactose intolerance, and others who consume no or minimal amounts of these foods might not obtain sufficient amounts of iodine [ 48 , 49 ]. People living in regions with iodine-deficient soils Iodine-deficient soils produce crops that have low iodine levels.
Mountainous areas e. People living in these areas are at risk of iodine deficiency unless they consume iodized salt or foods produced outside the iodine-deficient area. People with marginal iodine status who eat foods containing goitrogens Consumption of foods that contain goitrogens, substances that interfere with the uptake of iodine in the thyroid, can exacerbate iodine deficiency [ 2 ].
Foods high in goitrogens include soy, cassava, and cruciferous vegetables e. These issues are of concern primarily for people living in areas prone to iodine deficiency [ 6 ]. For most people, including most of the U. Due to its important role in fetal and infant development and thyroid hormone production, iodine is a critical nutrient for proper health at all life stages.
Fetal and infant development Iodine sufficiency during pregnancy is extremely important for proper fetal development. During early pregnancy, when fetal thyroid gland development is incomplete, the fetus depends entirely on maternal T4 and therefore, on maternal iodine intake [ 51 ]. Sufficient iodine intake after birth is also important for proper physical and neurological growth and maturation. Research suggests that infants are more sensitive to the effects of iodine deficiency than other age groups, as indicated by changes in their TSH and T4 levels in response to even mild iodine deficiency [ 53 ].
Although severe iodine deficiency disorders are uncommon in the United States, mild-to-moderate iodine insufficiency during pregnancy may subtly affect fetal development [ 4 , ]. A meta-analysis of 6, mother-child pairs from three birth cohorts in the Netherlands, Spain, and the United Kingdom found that verbal IQ assessed in children at 1.
Despite the importance of iodine for proper fetal development, the effects of iodine supplements during pregnancy on infant and child neurodevelopment in particular are inconclusive. Iodine supplementation had no effect on child cognitive, language, or motor scores [ 61 ]. One of these trials also assessed children at age 5?
Breast milk contains iodine, although concentrations vary based on maternal iodine levels. Infants who are exclusively breastfed depend on maternal iodine sufficiency for optimal development.
During the weaning period, infants not receiving iodine-containing complementary foods may also be at risk of iodine deficiency, even in countries with iodized salt programs [ 63 , 64 ].
To ensure that adequate amounts of iodine are available for proper fetal and infant development, several national and international groups recommend iodine supplementation during pregnancy, lactation, and early childhood. WHO recommendations for these countries also include breastfeeding through 24 months of age, combined with complementary foods fortified with iodine for children between the ages of 7—24 months [ 7 ]. Similarly, the American Academy of Pediatrics recommends that women who are pregnant, planning to become pregnant, or lactating take a daily supplement providing at least mcg iodine and use iodized salt [ 66 ].
The use of iodine-containing dietary supplements by pregnant and lactating women in the United States appears to be low compared to current recommendations.
Of 59 best-selling prenatal multivitamin supplements on the market in —, only 34 contained iodine [ 22 ]. The median iodine content was mcg per daily serving, with a range of 25 to mcg; 25 of the 34 provided iodine as potassium iodide. Results from a study however, raise some questions as to the safety of widespread iodine supplementation in areas of relative iodine sufficiency.
These findings suggest that taking higher doses of supplemental iodine during pregnancy could induce thyroid dysfunction in some women and underscore the need for additional research into the effects on maternal thyroid function of iodine supplementation during pregnancy.
Many researchers, as well as the American Thyroid Association, stress the importance of continued iodine status monitoring among women of reproductive age [ 1 , 4 , 31 , 37 , 55 , 69 , 70 ]. Cognitive function during childhood The effects of severe iodine deficiency on neurological development are well documented. Results from several studies suggest, for example, that chronic, moderate-to-severe iodine deficiency, particularly in children, reduces IQ by about 12— A Cochrane review concluded that iodine supplementation in children living in areas of iodine deficiency appears to both positively affect physical and mental development and decrease mortality with only minor and transient adverse effects [ 71 ].
The effects of mild iodine deficiency during childhood are more difficult to quantify. Some research suggests that mild iodine deficiency is associated with subtle neurodevelopmental deficits and that iodine supplementation might improve cognitive function in mildly iodine-deficient children [ 51 ]. These findings suggest that correcting mild iodine deficiency in children could improve certain components of cognition.
Additional research is required to fully understand the effects of mild iodine deficiency and iodine supplementation on cognitive function. Fibrocystic breast disease Fibrocystic breast disease is a benign condition characterized by lumpy, painful breasts and palpable fibrosis. It commonly affects women of reproductive age, but it can also occur during menopause, especially in women taking estrogens [ 73 ].
Breast tissue has a high concentration of iodine, especially during pregnancy and lactation [ 4 , 74 ]. Some research suggests that iodine supplementation might be helpful for fibrocystic breast disease, although a specific mechanism of action has not been established [ 75 ] and data are limited. A more recent randomized, double-blind, placebo-controlled clinical trial had similar findings. In this study, researchers randomly assigned women 18—50 years of age with fibrosis and a history of breast pain to receive tablets containing 0 mcg, 1, mcg, 3, mcg, or 6, mcg of iodine per day [ 75 ].
After 5 months of treatment, women receiving doses of 3, or 6, mcg iodine had a significant decrease in breast pain, tenderness, and nodularity compared with those receiving placebo or 1, mcg iodine. The researchers also reported a dose-dependent reduction in self-assessed pain. None of the doses was associated with major adverse events or changes in thyroid function test results.
Moreover, the doses used in these studies approximately 1,—6, mcg per day are several times higher than the iodine UL of 1, mcg for adults. Doses of this magnitude should only be used under the guidance of a physician [ 2 ].
Radiation-induced thyroid cancer Nuclear accidents can release radioactive iodine into the environment, increasing the risk of thyroid cancer in exposed individuals, especially children [ 77 , 78 ]. Thyroidal uptake of radioactive iodine is higher in people with iodine deficiency than in people with iodine sufficiency. For this reason, iodine-deficient individuals have a particularly high risk of developing radiation-induced thyroid cancer when exposed to radioactive iodine.
The FDA has approved potassium iodide as a thyroid-blocking agent to reduce the risk of thyroid cancer in radiation emergencies involving the release of radioactive iodine [ 77 ]. The FDA recommends that exposed people take a daily pharmacological dose 16— mg potassium iodide, depending on age until the risk of significant radiation exposure ends [ 77 , 78 ]. Potassium iodide was widely used in Poland following the Chernobyl accident and childhood thyroid cancer rates did not increase substantially in subsequent years [ 79 ].
In areas where iodide prophylaxis was not used, such as Belarus and Ukraine, where many children were mildly iodine-deficient, the incidence of thyroid cancer sharply increased among children and adolescents [ 77 ]. High intakes of iodine can cause some of the same symptoms as iodine deficiency—including goiter, elevated TSH levels, and hypothyroidism—because excess iodine in susceptible individuals inhibits thyroid hormone synthesis and thereby increases TSH stimulation, which can produce goiter [ 2 , 80 ].
Iodine-induced hyperthyroidism can also result from high iodine intakes, including when iodine is administered to treat iodine deficiency. Studies have also shown that excessive iodine intakes cause thyroiditis and thyroid papillary cancer [ 2 , 80 ].
Cases of acute iodine poisoning are rare and are usually caused by doses of many grams. Acute poisoning symptoms include burning of the mouth, throat, and stomach; fever; abdominal pain; nausea; vomiting; diarrhea; weak pulse; and coma [ 2 ]. Responses to excess iodine and the doses required to cause adverse effects vary [ 81 ]. Some people, such as those with autoimmune thyroid disease and iodine deficiency, may experience adverse effects with iodine intakes considered safe for the general population [ 2 , 5 ].
In most people, iodine intakes from foods and supplements are unlikely to exceed the UL [ 2 ]. Long-term intakes above the UL increase the risk of adverse health effects. The ULs do not apply to individuals receiving iodine for medical treatment, but such individuals should be under the care of a physician [ 2 ].
Iodine supplements have the potential to interact with several types of medications. A few examples are provided below. Individuals taking these medications on a regular basis should discuss their iodine intakes with their healthcare providers. Taking high doses of iodine with anti-thyroid medications can have an additive effect [ 81 ] and could cause hypothyroidism.
Taking potassium iodide with ACE inhibitors can increase the risk of hyperkalemia elevated blood levels of potassium [ 81 ]. The federal government's — Dietary Guidelines for Americans notes that "Because foods provide an array of nutrients and other components that have benefits for health, nutritional needs should be met primarily through foods. In some cases, fortified foods and dietary supplements are useful when it is not possible otherwise to meet needs for one or more nutrients e.
For more information about building a healthy dietary pattern, refer to the Dietary Guidelines for Americans and the U. Department of Agriculture's MyPlate. This fact sheet by the Office of Dietary Supplements ODS provides information that should not take the place of medical advice. We encourage you to talk to your healthcare providers doctor, registered dietitian, pharmacist, etc.
Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice.
Updated: March 29, History of changes to this fact sheet. Find ODS on:. Strengthening Knowledge and Understanding of Dietary Supplements. Health Information Health Information. Iodine Fact Sheet for Health Professionals. Health Implications of Perchlorate Ingestion. Institute of Medicine, Food and Nutrition Board. World Health Organization. Assessment of iodine deficiency disorders and monitoring their elimination.
Geneva, Switzerland: WHO, Patrick L. Iodine: deficiency and therapeutic considerations. Altern Med Rev. Iodine deficiency. Endocr Rev. Iodine-deficiency disorders. Prevention and control of iodine deficiency in pregnant and lactating women and in children less than 2-years-old: conclusions and recommendations of the Technical Consultation.
Public Health Nutr. If a person doesn't consume enough iodine, they can become iodine deficient. The lack of this micronutrient can cause different medical problems usually due to hypothyroidism caused by a thyroid that does not make enough hormones. These conditions include goiter a visible swelling of the thyroid as well as serious birth defects. In fact, iodine deficiency is the most common preventable cause of mental retardation.
Iodine in the form of iodide is added to table salt to help prevent iodine deficiency. Since the s there have been efforts to have universal salt iodization.
This has been an affordable and effective way to combat iodine deficiency around the world, but not all salt contains iodine, however. You'll investigate whether different salts have iodine by mixing them with laundry starch, which forms a blue-purple—colored chemical with iodine. Vinegar and hydrogen peroxide are added to the salt solution to help this chemical reaction take place.
Alternatively, you could use smaller cups and scale down the activity. If the iodine doesn't come with a dropper, you'll also need a medicine dropper. To do this, pour one half cup of distilled water into a disposable cup, add one half teaspoon tsp. Be careful when handling the iodine because it can stain. What happens to the liquid when the iodine is added? Add one cup of distilled water to the salt and stir well for about a minute with a clean, disposable plastic spoon.
You do not need all of the salt to dissolve. What do you think the purpose of the starch is? What happens to the solution after you stir it? Does it become a blue-purple color? For each type, be sure to use a different, clean disposable cup and spoon. Do any of the other salt solutions become a blue-purple color?
Do your results agree with the labeling on the salt packages, which often say whether the salt contains iodide or not? Iodine is an element found mainly in seawater and in soil close to the sea. The human body needs iodine to make thyroid hormone. During fetal development, infancy, and childhood, thyroid hormone is essential for the brain and nervous system to develop normally. Too little iodine, and thus too little thyroid hormone, can lead to mental retardation, dwarfism, hearing loss, and other problems.
Later in life, thyroid hormone controls metabolism. Adults who don't take in enough iodine can develop a goiter a swelling of the butterfly-shaped thyroid gland in the neck , and the low output of thyroid hormone can lead to sluggish metabolism, poor thinking skills, infertility, thyroid cancer, and other conditions. Goiter was once a big problem in wide swaths of the United States.
In the early s, Dr. David Marine of the Cleveland Clinic described goiter as "one of the most important causes of physical and mental degeneracy with which society has had and still has to deal.
Borrowing an idea from the Swiss, a group of U. Iodized salt was first sold in Michigan in May , and across the nation later that year. In the U. In the s and s, the use of iodine-based disinfectants in the dairy industry and iodine-based conditioners in the commercial baking industry put many Americans on track to getting too much iodine.
The situation has stabilized in recent years, with national nutrition surveys showing that most Americans get enough iodine, and only small numbers get too little or too much.
Current dietary guidelines recommend that men and women ages 19 and older get micrograms of iodine a day. Women who are pregnant should get micrograms, and women who are breast-feeding an infant should get micrograms. Most Americans take in more sodium than they need.
Almost all of it comes from salt. The so-called hidden salt in processed food is a great place to start trimming sodium from your diet, and cutting back on it will have little effect on your iodine intake. To get all your iodine from salt, you would need more than half a teaspoon of iodized salt a day.
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