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Iodine is a micronutrient3 used by the thyroid gland in order for it to function properly. It is produced in trace amounts by the body and is sustained through the diet or supplements.  The thyroid gland is essential for the development of other associated hormones.  These hormones regulate metabolism as well as how the body uses fats and carbohydrates, body temperature, heart rate, and the production of proteins. The pituitary gland and hypothalamus tell the body how much of these hormones should be produced and when to release them.

Where to Find Iodine

Iodine1 can be found in sea water and rain that mixes with ground water in the soil. That means if you enjoy eating seaweed, you are taking in the best and most organic form of the nutrient. If that proposition seems unpalatable, Iodine appears in other food groups in varying amounts like some dairy products and some fruits and vegetables. But most people get the right amount of iodine from use of iodized table salt or supplements.

Supplemental Names for Iodine

If the thyroid gland is functioning properly, it uses the right amount of iodine. But since it is such an essential nutrient and deficiencies can occur from either too much or too little iodine in the body, supplements may be required or even necessary.  There’s many types of iodine but the main derivative is potassium iodide, which can come in tablet form but might inhibit the amount of iodine absorbed by the thyroid.

Benefits of Iodine

Iodine can aid in physical and psychological development as well as disease prevention. While children and adults need it, iodine is especially important to pregnant women and a developing fetus’s brain and cognitive development.  Iodine can also help the thyroid so it is stimulated correctly by the thyroid hormone thyrotropin, which is secreted by the pituitary gland. This secretion protects the body from hypothyroidism that may lead to a goiter. The micronutrient can also play a role in strengthening the immune system against mammary dysplasia or fibrocystic breast disease.

How to Use and Take Iodine

Other than its usage by pregnant women or by those suffering from an iodine deficiency, iodine has other beneficial uses. Radioactive iodine, for example, can be used for treating thyroid cancer. Povidone iodine (also known as betadine) is used for treating problems with the eyes. Iodine can also be used for water disinfection in different areas of the world. Iodine has even been used to induce growth and relieve the stress of growing plants. Iodine usually comes in pill or liquid (dropper) form and may go by other names, such as iodide or iodate.

Daily Recommended Allowance

Understanding the right amounts of iodine adults and children should ingest daily is important for following daily allowances of it in food or as a supplement2. Children and adults should have 100 – 199 micrograms (mcg) daily, 150 – 249 for pregnant women. Anything less than 100 micrograms in children and adults would indicate an insufficient amount. The recommendation for iodine intake is overseen by the Food and Nutrition Board (FNB). It says, based on the board’s Dietary Reference Intake (DRI) measures, that the recommended daily allowance is as follows:

  • Birth to 6 months of age – 110 mcg for both males and females.
  • 7 – 12 months – 130 mcg for both males and females.
  • 1 – 8 years – 90 mcg for both males and females.
  • 9 – 13 years – 130 mcg for both males and females.
  • 14 – 19 years and up – 150 mcg, 220 mcg during pregnancy, 290 mcg if a woman is lactating.

If iodine levels fall below the recommended 100 mcg per day, then an iodine deficiency or disorder can occur, which can lead to hypothyroidism or a goiter.

Iodine Deficiency Symptoms and Who Is at Risk

Symptoms of a deficiency can be wide ranging, but some of them are weight gain, fatigue, hair loss, dry or flaking skin, fluctuations in heart rate, etc. The two main groups at risk for iodine deficiency are pregnant women and their developing fetus or newborns. Pregnant women can experience issues during pregnancy, such as miscarriage, or heavy or irregular periods. Children, especially a developing fetus or infant, can be born with learning problems, mental retardation or cretinism.

Major Symptoms: Goiter and Hypothyroidism

Iodine is present in a healthy human body in very small amounts, about 15 – 20 micrograms. A high percentage of that is in the thyroid gland, so it is enough to keep the thyroid functioning until supplied and boosted by diet or a supplement. Lack of enough iodine can lead to the two most prevalent problems as a result of deficiency: hypothyroidism and goiter. The two symptoms are related in terms of deficiency but are not the same by definition.

How Goiter and Hypothyroidism Occur

Iodine secreted by the pituitary gland is absorbed by the thyroid, which works to uptake it in a repetitive way. If the thyroid overworks as a result of not enough iodine being present, this is when it enlarges and can become a goiter4.  Just as problematic but even more severe is hypothyroidism5. It occurs when there is not enough iodine available to produce or support thyroid hormones. The resulting effects on muscle, heart, liver, kidney, and a developing brain can be detrimental. Both of these symptoms can result in people or environments where the presence of iodine is inadequate. Worldwide6, 18 million babies are born with mental retardation, 38 million are born with a risk of it, and 2 million people are subject to or have an iodine deficiency.

Dietary Sources of Iodine

Since only low levels of iodine are produced by the body, most people of the world receive their daily allowance of it through iodized salt or assistance from a supplement. Ninety percent of iodine absorption7 comes from water and certain foods, such as seaweed and fish. Other foods that contain iodine are green vegetables and spinach, especially if grown in soil with a high iodine content, and it is also present in smaller amounts in some dairy, meats, and cereals.

Citations and Sources

NIH S. Iodine. NIH Office of Dietary Supplements.
Medlineplus S. Simple Goiter. Home -- Medical Encyclopedia -- Simple Goiter.
Medlineplus S. Hypothyroidism. Home -- Medical Encyclopedia -- Hypothyroidism.
Kapil U. Health Consequences of Iodine Deficiency. Sultan Qaboos Univ Med J. 2007;7(3):267-272. [PMC]
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