iodine

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http://www.whfoods.com/genpage.php?tname=nutrient & dbid=69 iodine What can high-iodine foods do for you? Help ensure proper thyroid gland functioning What events can indicate a need for more high-iodine foods? Goiter (enlargement of the thyroid gland) Fatigue Weakness Depression Weight gain Concentrated food sources of iodine include sea vegetables, yogurt, cow's milk, eggs, strawberries and mozzarella cheese. Fish and shellfish can also be concentrated sources of iodine. For serving size for specific foods, see Nutrient Rating Chart

below at the bottom of this page. Description Function Deficiency Symptoms Toxicity Symptoms Cooking, storage and processing Factors that affect function Drug-nutrient

interaction Nutrient interaction Health conditions Supplements Food Sources Public Recommendations References Description What is Iodine? If you backpack in the mountains, you may have used iodine tablets to purify your drinking water. Or, perhaps you've used an

iodine-based disinfectant to clean a minor skin wound. But did you know that iodine is essential to life? Iodine, a trace mineral, is required by the body for the synthesis of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3). (T4 contains 4 iodine atoms. When one of the iodine atoms is stripped off of T4, it becomes T3, with 3 iodine atoms remaining.) Under normal circumstances, your body contains approximately 20 to 30 mg of iodine, most of which is stored in your thyroid gland, located in the front of your neck, just under your voice box. Smaller amounts of iodine are also found in lactating mammary glands, the stomach lining, salivary glands, and in the blood. How it Functions What is the function of iodine? As a component of the thyroid hormones thyroxine (T4) and triiodothyronine (T3), iodine is essential to human life. Without sufficient iodine, your

body is unable to synthesize these hormones, and because the thyroid hormones regulate metabolism in every cell of the body and play a role in virtually all physiological functions, an iodine deficiency can have a devastating impact on your health and well-being. Regulating thyroid hormones The synthesis of thyroid hormones is tightly controlled. When the amount of thyroid hormone in your blood drops, the pituitary gland secretes a hormone called thyroid-stimulating hormone (TSH). As its name suggests, TSH then stimulates the thyroid gland to increase its uptake of iodine from the blood, so that more thyroxine (T4) can be synthesized. When necessary, thyroxine is then converted to the metabolically active triiodothyronine (T3), a process that involves removing one iodine atom from T4. Several other physiological functions for iodine have been suggested. Iodine may help inactivate bacteria, hence its use as a skin disinfectant

and in water purification. Iodine may also play a role in the prevention of fibrocystic breast disease, a condition characterized by painful swelling in the breasts, by modulating the effect of the hormone estrogen on breast tissue. Finally, researchers hypothesize that iodine deficiency impairs the function of the immune system and that adequate iodine is necessary to prevent miscarriages. Deficiency Symptoms What are deficiency symptoms for iodine? In the early part of the 20th century, iodine deficiency was quite common in the United States and Canada. However, this problem has since been almost completely resolved by the use of iodized salt. In addition, iodine is now added to animal feed, which has increased the iodine content of commonly consumed foods, including cow's milk. Unfortunately, in countries where iodized salt is not commonly consumed, iodine

deficiency remains a signficant problem. Dietary deficiency of this vital mineral results in decreased synthesis of thyroid hormone. Goiter, or enlargement of the thyroid gland, is usually the earliest symptom of iodine deficiency. The enlargement of the thyroid results from overstimulation of the thyroid gland by thyroid stimulating hormone (TSH), as the body attempts to produce thyroid hormones despite the lack of available iodine. Goiter is more common in certain geographical areas of the world, and is attributed to lack of iodine in the diet as well as to the consumption of certain foods, called goitrogens, that block the absorption and utilization of iodine. These foods include cruciferous vegetables, soy products, cassava root, mustard, and millet. Drinking water obtained from contaminated wells may also contain goitrogenic substances. Iodine deficiency may eventually lead to hypothyroidism, which causes a variety of symptoms including fatigue,

weight gain, weakness and/or depression. Interestingly, iodine deficiency can also cause hyperthyroidism, a condition characterized by weight loss, rapid heart beat, and appetite fluctations. Severe iodine deficiency during pregnancy or infancy causes cretinism, a condition characterized by hypothyroidism leading to failure of the thyroid gland and/or severe mental retardation, stunted physical growth, deafness, and spasticity. If discovered in its initial stages, cretinism can be corrected with iodine supplementation. Toxicity Symptoms What are toxicity symptoms for iodine? Accidental overdose of iodine from medications or supplements in amounts exceeding one gram may cause burning in the mouth, throat and stomach and/or abdominal pain, nausea, vomiting, dirarrhea, weak pulse, and coma. It is difficult to take in too much iodine from food sources alone. It is

estimated that men and women consume at most 300 mcg and 210 mcg of iodine per day, respectively. In general, even high intakes of iodine from food are well-tolerated by most people. However, in certain circumstances, excessive consumption of iodine can actually inhibit the synthesis of thyroid hormones, thereby leading to the development of goiter (enlargement of the thyroid gland) and hypothyroidism. Excessive iodine intake may also cause hyperthyroidism, thyroid papillary cancer, and/or iodermia (a serious skin reaction). In an attempt to prevent these symptoms of iodine toxicity, the Institute of Medicine established the following Tolerable Upper Intake Levels (TUL) for iodine: 1-3 years: 900 mcg 4-8 years: 300 mcg 9-13 years: 600 mcg 14-18 years: 900 mcg 19 years and older: 1,100 mcg Pregnant women 14-18 years: 900 mcg Pregnant women 19 years and older: 1,100 mcg Lactating women 14-18 years: 900 mcg Lactating women 19 years and older: 1,100 mcg It is important to note that if you have an autoimmune thyroid disease (for example, Grave's disease or Hashimoto's disease) or if you have experienced an iodine deficiency at some point in your life, you may be more susceptible to the dangers of excessive iodine consumption, and may, therefore, need to monitor your intake of iodine more carefully. Impact of Cooking, Storage and Processing How do cooking, storage, or processing affect iodine? Food processing practices often increase the amount of iodine in foods. For example, the addition of potassium iodide to table salt to produce "iodized" salt has dramatically increased the iodine intake of people in developed countries. In addition, iodine-based dough conditioners are commonly used in commercial bread-making, which increases the iodine

content of the bread. Factors that Affect Function What factors might contribute to a deficiency of iodine? The absorption and/or utilization of iodine is inhibited by components of certain foods. These food components, called goitrogenic compounds, are found primarily in cruciferous vegetables (for example, cabbage and broccoli), soybean products, cassava root, peanuts, mustard, and millet. Over consumption of these foods may lead to thyroid problems by reducing the amount of available iodine for the manufacture of thyroid hormones. It is believed that cooking can inactivate the goitrogenic compounds in these foods, thereby eliminating their negative impact on iodine status. Drug-Nutrient Interactions What medications affect iodine? Amiodarone, a drug most

commonly sold under the brand name Cordarone , is sometimes used to treat irregular heart beat. This medication contains iodine and can disrupt proper thyroid function. Similarly, erythrosine, a red coloring agent commonly used in foods and medications, also contains significant amounts of iodine and may also impact thyroid activity. Nutrient Interactions How do other nutrients interact with iodine? The conversion of thyroxine (T4) to triiodthyronine (T3) requires the removal of an iodine molecule from T4. This reaction requires the mineral selenium. The iodine molecule that is removed gets returned to the body's pool of iodine and can be reused to make additional thyroid hormones. If your body is deficient in selenium, the conversion of T4 to T3 is slowed, and less iodine is

available for the thryoid to use in making new hormones. Animal studies have shown that arsenic interferes with the uptake of iodine by the thyroid, leading to goiter. In addition, dietary deficiency of vitamin A, vitamin E, zinc and/or iron can exaggerate the effects of iodine deficiency. Health Conditions What health conditions require special emphasis on iodine? Iodine may play a role in the prevention and/or treatment of the following health conditions: Cognitive impairment Cretinism Fibrocystic breast disease Goiter Hyperthyroidism Hypothyroidism Multiple miscarriages Form in Dietary Supplements What forms of iodine are found in dietary supplements? The elemental form of iodine is available in dietary supplements as iodine caseinate and in products that contain kelp. Many supplements contain iodine complexed with potassium or sodium, called potassium iodide or sodium iodide, respectively. Food Sources What foods provide iodine? The amount of iodine found in most natural foods is typically quite small and varies depending on environmental factors such as the soil concentration of iodine and the use of fertilizers. Some of the richest food sources of iodine are often processed foods that contain iodized salt, and breads that contain iodate dough conditioners. Sea vegetables are an excellent source of iodine. Yogurt, cow's milk, eggs, and strawberries are very good sources of idone. Good sources include mozzarella cheese. Fish and shellfish require their own special category when it comes to iodine content, because the amount of iodine they contain is not always easy to predict. For example, the amount of iodine found in fish may not match up very predictably with the amount found in their home waters, or even with their diet. Four ounces of very low iodine fish might only provide about 70 micrograms of iodine, or less than half of the adult RDA. By contrast, four ounces of very high iodine fish might contain as much as 1,000 micrograms of iodine - an amount just below the Tolerable Upper Limit (UL, or safety level) of 1,100 micrograms. Due to the great variability in fish iodine content, and the relative lack of good information for consumers to base their nutritional decisions in this area, we would not

recommend reliance on fish alone to provide all of your dietary iodine needs. However, you can count on getting iodine from most fish, and on any one particular day, we would recommend thinking about a 4-6 ounce fish meal serving as providing at least 50% of your iodine needs. Conversely, if you are trying to greatly restrict your iodine intake, you might want to eat fish on a less frequent basis to lower your risk of iodine intake above the RDA level. Introduction to Nutrient Rating System Chart In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the World's Healthiest Foods that are either an excellent, very good, or good source of iodine. Next to each food name, you'll find the serving size we

used to calculate the food's nutrient composition, the calories contained in the serving, the amount of iodine contained in one serving size of the food, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system. World's Healthiest Foods ranked as quality sources of:iodine Food ServingSize Cals Amount(mcg)

DV(%) NutrientDensity World'sHealthiestFoods Rating Kelp (sea vegetable) 0.25 cup 8.6 415.00 276.7 579.1 excellent Yogurt, low-fat 1 cup 155.1 87.22 58.1 6.8 very good Cow's milk, 2% 1 cup 121.2 58.56 39.0 5.8 very good Egg, whole, boiled 1 each 68.2 23.76 15.8 4.2 very good Strawberries 1 cup 43.2 12.96 8.6 3.6 very good Mozzarella cheese, part-skim, shredded 1 oz-wt 72.1 10.09 6.7 1.7 good World's HealthiestFoods Rating Rule excellent DV>=75% OR Density>=7.6 AND DV>=10% very good DV>=50% OR Density>=3.4 AND DV>=5% good DV>=25% OR Density>=1.5 AND DV>=2.5% Public Health Recommendations What are current public health recommendations for iodine? In 2000, the Institute of Medicine at the National Academy of Sciences developed new Dietary Reference Intakes for iodine. Adequate Intakes were established for children up to one year old, and Recommended Dietary Allowances were determined for all people over one year old. These recommendations appear below: 0-6 months: 110 mcg 7-12 months: 130 mcg 1-8 years: 90 mcg Boys 9-13 years: 120 mcg Girls 9-13 years: 120 mcg Boys 14-18 years: 150 mcg Girls 14-18 years: 150 mcg Men

19 years and older: 150 mcg Women 19 years and older: 150 mcg Pregnant women 14 years and older: 220 mcg Lactating women 14 years and older: 290 mcg