What Is It?
Concentrated primarily in the thyroid gland, iodine is a potent trace mineral that plays an important role in many of the body’s biological functions. In fact, iodine is so vital to a person’s overall health that in the 1920s U.S. government health officials recommended it be added to table salt.
The ruling was a strategy to ensure that an iodine deficiency didn’t develop in the American diet. And it worked. Today, iodine deficiency has been virtually eliminated domestically. Unfortunately, about 1.6 billion people, mainly in underdeveloped countries are still plagued by a variety of disorders caused by a lack of this mineral in their diets.
The primary function of iodine is to keep the thyroid gland healthy and capable of manufacturing thyroxine, a vital hormone needed throughout the body. This hormone helps to regulate metabolism (how quickly and efficiently calories are burned), to control the physical and mental growth of children (insufficient iodine in a pregnant woman can cause cretinism in a fetus), and to break down fats and proteins.
In these and many other ways, iodine is, at least indirectly, responsible for maintaining some of the most fundamental biological functions of the body.
Insufficient iodine (which results in too little thyroxine) can lead to such symptoms as fatigue, dry skin, an increase in blood fats, a hoarse throat, delayed reflexes, and reduced mental clarity.
As much as 75% of the body’s iodine is stored in the butterfly-shaped thyroid gland in the front of the throat; the rest is distributed throughout the body. If a person is iodine-deficient, a goiter (a large growth at the base of the neck) may develop as the thyroid works overtime trying to make enough thyroxine hormone for the body to function normally. Interestingly, in rare cases, taking an excessive amount of iodine will enlarge the gland and cause a goiter as well.
Recently, international-aid researchers reported the pooled results of 10 studies carried out in countries where iron-deficiency disorders are common. They found multiple consequences of inadequate iodine in children, including impaired motor skills, diminished muscle strength and coordination, poor manual dexterity, and other problems.
Dietary sources of iodine are plentiful. For most Americans, a deficiency in iodine is not a risk. One teaspoon of iodized salt contains more than 300 mcg of iodine, so it is not difficult to obtain or exceed the small amount needed to meet the daily requirement. The RDA for iodine is 150 mcg a day for adults.
Other sources of iodine include dairy products made from milk produced by cows grazing in coastal soil, as well as fruits and vegetables grown in coastal soil. Various vegetables from the sea, such as kelp and seaweed, contain very high amounts of iodine as well. Commercially prepared baked goods, such as cakes and breads, frequently contain dough conditioners that have iodine. Most salty, high-sodium processed snack foods, however, contain very little iodized salt and almost no iodine.
The trace mineral is also found in most multivitamin and mineral supplements. Concentrated sea kelp tablets are another potent source of iodine.
General Interaction
Combining iodine with such anti-thyroid drugs as methimazole and propylthiouracil may lessen the effect of these medications.
Don’t take iodine at the same time as the anti-manic agent lithium; adverse interactions may occur.
Consuming large amounts of kelp, which contains iodine, may decrease the effectiveness of anti-thyroid agents.
Note: For more information on interactions with specific generic drugs, see the Reference Library on Strong iodine.
Cautions
Don’t take any iodine unless your doctor specifically prescribes it.
Virtually no cases of thyroid underactivity (hypothyroidism) are caused by iodine deficiency. If you think you have an underactive thyroid, see your doctor for testing. Taking iodine-containing supplements like kelp will not help an underactive thyroid.
In extremely high doses–greater than 30 times the standard recommended amount of iodine–adverse reactions may develop. These can include mouth sores, a metallic taste in the mouth, swollen salivary glands, vomiting, headache, and rash.
Don’t depend on salted snacks as an iodine source; many, including pretzels and chips, are not made with iodized salt. And check the label to be sure that any sea salt you buy is iodized; many brands are not and thus are not an adequate source of iodine. On the other hand, recent reports from Hong Kong indicate that many children were overdosing on iodine because of the popularity of roasted seaweed snacks; certain brands contain extremely high levels of the mineral.
Be well,
David Edelberg, MD