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.
Pennington JA, Young B. Iron, zinc, copper, manganese, selenium, and iodine in foods from the United States Total Diet Study. These hormones control your metabolic rate the rate at which your body uses energy when it is resting. They also help your brain and body grow and develop.
The amount of iodine available in these foods depends on where the food was grown and how it was made. Iodine can also come from iodised salt added during or after cooking. In Australia, since , all commercial bread products except for organic bread and bread mixes for making bread at home have had iodised salt added to them instead of non-iodised salt to increase the amount of iodine they contain.
This is known as fortifying the bread with iodine. This means that most of the Australian population, apart from pregnant women, is now consuming enough iodine to meet their needs.
The best way to get the nutrients your body needs is as part of a healthy, well-balanced diet. The Australian Guide to Healthy Eating provides advice on recommended amounts of food from each of the five food groups. Eating according to this guide provides enough iodine for most people. However, before starting on iodine supplements, see your doctor as too much iodine can be harmful, especially if you have an underlying thyroid disorder. If your diet is too low in iodine, your thyroid gland gets larger and larger to try to trap more iodine from the bloodstream so it can make more thyroid hormones.
This overgrowth of the thyroid gland is called goitre. What happens if I take too much iodine? This can lead to a wide range of different symptoms, such as weight gain. If you take iodine supplements, do not take too much as this could be harmful. Taking 0. Iodine is a micronutrient required for normal thyroid function. Recommended Daily Allowances RDA for iodine intake are mcg in adults, mcg in pregnant women, and mcg in breastfeeding women in the U.
The U. During pregnancy and lactation, women require higher amounts of iodine for the developing fetus and infant. The American Thyroid Association recommends that women take a multivitamin containing mcg iodine daily in the form of potassium iodide KI 3 during preconception, pregnancy, and lactation to meet these needs 4.
Ingestion of greater than 1, mcg of iodine per day Tolerable Upper Limits for iodine 1 is not recommended and may cause thyroid dysfunction. During pregnancy and lactation, the recommendations for the upper limit vary and range from , mcg of iodine daily 2.
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