Dairy products contain iodine. However, the amount of iodine in dairy products varies by whether the cows received iodine feed supplements and whether iodophor sanitizing agents were used to clean the cows and milk-processing equipment [ 9 ]. Plant-based beverages used as milk substitutes, such as soy and almond beverages, contain relatively small amounts of iodine.
Most commercially prepared bread contains very little iodine unless the manufacturer has used potassium iodate or calcium iodate as a dough conditioner [ 10 , 11 ]. Manufacturers list dough conditioners as an ingredient on product labels but are not required to include iodine on the Nutrition Facts label [ 12 ], even though these conditioners provide a substantial amount of iodine.
Pasta is not a source of iodine unless it is prepared in water containing iodized salt because it absorbs some of the iodine [ 11 ]. Most fruits and vegetables are poor sources of iodine, and the amounts they contain are affected by the iodine content of the soil, fertilizer use, and irrigation practices [ 2 , 10 ]. This variability affects the iodine content of meat and animal products because of its impact on the iodine content of foods that the animals consume [ 14 ].
The iodine amounts in different seaweed species also vary greatly. For these reasons, the values for the foods listed in Table 2 are approximate but can be used as a guide for estimating iodine intakes. The U. Food and Drug Administration FDA developed DVs to help consumers compare the nutrient contents of foods and dietary supplements within the context of a total diet. The DV for iodine is mcg for adults and children aged 4 years and older [ 12 ].
FDA does not require food labels to list iodine content unless iodine has been added to the food. The United States, Canada, and dozens of other countries have salt-iodization programs [ 3 , 16 , 17 ].
In the United States, salt manufacturers have been adding iodine to table salt since the s, although this practice is still voluntary [ 18 ]. The FDA has approved the use of potassium iodide and cuprous iodide for salt iodization [ 19 ], whereas the WHO recommends the use of potassium iodate due to its greater stability, particularly in warm, damp, or tropical climates [ 3 ].
However, most salt intake in the United States comes from processed foods, and food manufacturers almost always use non-iodized salt in these foods.
If they do use iodized salt, they must list the salt as iodized in the ingredient list on the food label [ 9 ]. Specialty salts, such as sea salt, kosher salt, Himalayan salt, and fleur de sel, are not usually iodized.
As shown in Table 2, non-iodized sea salt provides virtually no iodine [ 8 ]. In dietary supplements, iodine is often present as potassium iodide or sodium iodide [ 20 ].
Supplements containing kelp, a seaweed that contains iodine, are also available. A small study found that people absorb potassium iodide almost completely Dietary supplements containing only iodine are also available, and many contain high doses, sometimes above the UL [ 20 ]. Many dietary supplements that contain iodine are listed in the Dietary Supplement Label Database from the National Institutes of Health [ 20 ].
This database contains label information from tens of thousands of dietary supplement products on the U.
Through the TDS program, foods that represent the average U. These intakes meet or exceed the EAR for all groups. TDS data do not include iodine that people obtain from the discretionary use of iodized salt [ 25 , 26 ]. Because many U. Iodine status is typically assessed using urinary iodine measurements. Spot urine iodine measurements are a useful indicator of iodine status within populations [ 28 , 29 ].
However, multiple hour urinary iodine or multiple spot urine measurements are more accurate for individuals [ 4 , 30 ]. Much of this decline was a result of decreased levels of iodine in milk due to the reduced use of iodine-containing feed supplements and iodophor sanitizing agents in the dairy industry [ 33 ], as well as the reduced use of iodate dough conditioners by commercial bakers.
The use of erythrosine, an iodine-containing food dye commonly used in fruit-flavored breakfast cereals, also decreased during this time [ 33 ], though it is unclear to what extent this change actually affected urinary iodine levels because the bioavailability of iodine from erythrosine has been found to be low [ 34 ]. This sharp decline in urinary iodine levels caused some concern during the late s that the iodine sufficiency of the U. These values have essentially remained unchanged in the last three NHANES surveys, indicating that the dietary iodine intake of the general U.
Suboptimal iodine status during pregnancy has also been observed in Australia [ 38 ]. Pregnant women who do not consume dairy products may be particularly at risk of iodine insufficiency. Overall, it appears that the general U. Continued national iodine monitoring is needed with more emphasis on population subgroups that are most susceptible to iodine deficiency disorders. Iodine deficiency has multiple adverse effects on growth and development, and is the most common cause of preventable intellectual disability in the world [ 40 ].
Iodine deficiency disorders result from inadequate thyroid hormone production secondary to insufficient iodine [ 5 ]. During pregnancy and early infancy, iodine deficiency can cause irreversible effects. Under normal conditions, the body tightly controls thyroid hormone concentrations via TSH. TSH increases thyroidal iodine uptake from the blood and the production of thyroid hormone.
However, very low iodine intakes can reduce thyroid hormone production even in the presence of elevated TSH levels. Goiter is usually the earliest clinical sign of iodine deficiency [ 2 ]. In pregnant women, iodine deficiency of this magnitude can cause major neurodevelopmental deficits and growth retardation in the fetus, as well as miscarriage and stillbirth [ 5 ]. Chronic, severe iodine deficiency in utero causes cretinism, a condition characterized by intellectual disability, deaf mutism, motor spasticity, stunted growth, delayed sexual maturation, and other physical and neurological abnormalities [ 5 ].
In infants and children, less severe iodine deficiency can also cause neurodevelopmental deficits such as somewhat lower-than-average intelligence as measured by IQ [ 1 , 41 , 42 ].
Mild to moderate maternal iodine deficiency has also been associated with an increased risk of attention deficit hyperactivity disorder in children [ 43 ].
In adults, mild-to-moderate iodine deficiency can cause goiter as well as impaired mental function and work productivity secondary to hypothyroidism. Chronic iodine deficiency may be associated with an increased risk of the follicular form of thyroid cancer [ 44 ]. Thanks to a more national food supply, iodized salt, and other factors, overt iodine deficiency is now uncommon in North America.
International efforts since the early s have dramatically reduced the incidence of iodine deficiency worldwide, but some groups of people are still at risk of inadequate iodine intake.
Iodine insufficiency remains a public health problem in 25 countries with a total population of about million people [ 46 ]. The following groups are among those most likely to have inadequate iodine status. 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 ]. The thyroid gland is a butterfly-shaped endocrine gland that is normally located in the lower front of the neck. Thyroid hormone helps the body use energy, stay warm and keep the brain, heart, muscles, and other organs working as they should.
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. In the United States, iodine status has remained generally adequate in since the s although studies have shown that urinary iodine levels dropped by about half between the early s and the early s, and most recently mild iodine deficiency has re-emerged in pregnant women.
Iodine deficiency remains a major issue in other parts of the world, including parts of Europe, Africa and Asia. Iodine is present naturally in soil and seawater. The availability of iodine in foods differs in various regions of the world. Individuals in the United States can maintain adequate iodine in their diet by using iodized table salt, 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. 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.
Dairy products are major sources of iodine, especially in American diets When iodide enters the circulation, the thyroid gland concentrates it in appropriate amounts for thyroid hormone synthesis and most of the remaining amount is excreted in the urine [2]. The currently accepted minimum daily intake requirement for iodine is micrograms mcg. The recommended daily limit for iodine intake is micrograms for men and non-pregnant women.
The recommended daily intake is to micrograms for pregnant women and to micrograms for women who are breast-feeding. More items…. This might inflame the gland and cause a goiter, but not always. It could also thin your hair, dry your skin, and make you feel cold, tired, constipated, and depressed. Skip to content. Iodine levels were fold higher than what has been reported by other authors.
Iodine deficiency is widely recognized as the primary cause of goiter. Add sea salt, seafood, raw milk and eggs to your diet to avoid iodine deficiency, as this often also works as a preventative step of an enlarged thyroid gland. Studies have shown that iodine deficiency during infancy and pregnancy can interrupt healthy brain development and growth. Infants are more susceptible to mortality and high risk for neurodegenerative problems if iodine-deficient, such as a mental form of disability known as cretinism, motor function problems, learning disabilities and low growth rate.
To increase intake of iodine, try adding foods that are naturally high in iodine into your diet through the following recipes:. Iodine overdose of more than 2, milligrams could be dangerous, especially in individuals who are diagnosed with tuberculosis or kidney disease.
Iodine in excess could result in thyroid papillary cancer and hyperthyroidism rather than prevention. Pregnant women and nursing mothers should be cautious not to take iodine except in specifically prescribed doses. Josh Axe is on a mission to provide you and your family with the highest quality nutrition tips and healthy recipes in the world More Nutrition Dr.
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