Iodine Information

In depth research on essential vitamins.

Iodine is a chemical element (as are oxygen, hydrogen, and iron). It occurs in a variety of chemical forms, the most important being: iodide (I-); iodate (IO3-), and elemental iodine (I2). Iodine comes in three commercial forms, calcium iodide, potassium iodide, and sodium iodide. Iodized table salt usually makes up for any lack of it in the foods you consume.

Iodine affects the human body in many ways. It is known to be essential in maintaining the function of the thyroid and parathyroid glands in the human body. It is also essential to the production of thyroxine, a hormone associated with the thyroid gland and proper thyroid functioning.

The thyroid is a butterfly-shaped gland in the front part of the neck. It makes two hormones (thyroxine (T4) and triiodothyronine (T3)). The thyroid hormones are released into the bloodstream and carried by it to target organs, particularly the liver, kidneys, muscles, heart, and developing brain.

Iodine also promotes general growth and development within the body as well as aiding in metabolism. Iodine, because of it's role in the metabolism also helps to burn off excess fat.

Even though it is so important for proper functioning of the human organism, iodine deficiency is relatively common. Severe iodine deficiency often occurs in individuals who have thyroid disease and are hyperthyroid (an over active thyroid), or those who have a goiter from thyroid malfunction. Symptoms of iodine deficiency may include extreme fatigue, slowing of both physical and mental processes, weight gain, facial puffiness, constipation and lethargy.

Babies born to iodine deficient mothers may be lethargic and difficult to feed. If they are left untreated it is likely that they will develop cretinism and poor overall growth and mental retardation.

Recommended intakes of iodine widely vary, but the common agreement among professionals seems to be between 40 micrograms to 150 milligrams daily, which is usually obtained from dietary sources. Several international groups have made recommendations, which are fairly similar. ICCIDD, WHO, and UNICEF recommend the following daily amounts: age 0-7 years, 90 micrograms (mcg); age 7-12 years, 120 mcg; older than 12 years, 150 mcg; and pregnant and lactating women, 200 mcg.

Of course, before starting any form of supplementation you should consult your health care practitioner.
The most damaging effects of iodine deficiency are seen on fetal and infant development. Maternal iodine deficiency causes miscarriages, other pregnancy complications, and infertility. Thyroid hormones, and therefore iodine, are essential for normal development of the brain. If the fetus or newborn is not exposed to enough thyroid hormone, it may have permanent mental retardation, even if it survives.

Low birth weights and decreased child survival also result from iodine deficiency. Cretinism is a very severe degree of this brain damage; it includes permanent dense mental retardation, and varying degrees of additional developmental defects such as deaf/mutism, short stature, spasticity, and other neuromuscular abnormalities.

The most visible consequence of iodine deficiency is goiter. This word means "an enlarged thyroid." The process begins as an adaptation in which the thyroid is more active in its attempts to make enough thyroid hormone for the body's needs, despite the limited supply of raw material (iodine), much as a muscle gets bigger when it has to do more work.
If this adaptation is successful and the iodine deficiency is not too severe, the person may escape with only an enlarged thyroid and no other apparent damage from the iodine deficiency. Older individuals with goiters may develop nodules (lumps) in their thyroids, and sometimes these can begin making too much thyroid hormone when suddenly exposed to iodine.

This result occurs because these nodules are independent of usual controls; they make thyroid hormone at their own rate, and may over-produce it when given more iodine. Also, the nodular goiters in iodine deficiency have an increased rate of one type of thyroid cancer, called "follicular cancer." Goiters can sometimes enlarge enough to produce compression of other neck structures and may need surgical removal for that reason.

Most people who have previously been iodine sufficient can safely tolerate fairly large amounts. As mentioned above, some individuals have thyroid nodules that escape the body's usual controls, and they can start making too much thyroid hormone when their dietary iodine increases, to produce a condition called iodine-induced hyperthyroidism. Iodine excess can also cause thyroid underactivity, because large amounts of iodine block the thyroid's ability to make hormones. Individuals vary widely in their tolerance to iodine. Most people can handle large amounts satisfactorily, but there are exceptions. People with a tendency towards so-called autoimmune thyroid diseases, such as Graves' disease or Hashimoto's thyroiditis, or who have family members with these problems, may be more sensitive to iodine.

Most people can tolerate at least 1 mg (1000 mcg) of iodine daily without adverse effects. People with underlying autoimmune thyroid disease or who have previously been iodine deficient may tolerate less iodine. Iodine excess is undesirable, but its consequences are not nearly so severe as those of iodine deficiency, because the latter affects human development and can produce permanent brain damage. Properly iodized salt will rarely add more than about 300 mcg iodine daily to the diet. Therefore, concern about iodine excess is not a reason to stop or avoid consumption of iodized salt.

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