Iodine (why the fuss?)

++ Since the earthquake and ensuing disasters in Japan, we've been hearing more about iodine. Most of this has centered on radioactive iodine and on using salts of iodine to prevent radiation sickness.  At the heart of both of these concerns is iodine's unique relationship to the thyroid gland.  Although iodine is found in many parts of the body, most of it is in hormones produced by the thyroid gland.  This is such a tight relationship that when you eat a food with iodine in it, the thyroid  grabs it, in preference to any other gland in the body.  Oncologists use this to their advantage:  in treating thyroid cancer, they use radioactive iodine instead of other ways of administering radiation, knowing that the body will concentrate the radioactivity right where they want it.
  Obviously, if you don't want most of the thyroid destroyed, you want to avoid radioactive iodine - and this where the concern lies over fall-out from a damaged nuclear reactor.  Taking a larger dose of iodine (as in using iodine salts, such as Potassium Iodide) can help crowd out the amount of radioactive iodine the thyroid absorbs, but over-dosing can lead to Grave's Disease and to severe gastro-intestinal problems.  In most of the world right now, taking iodine salts because of worry about radiation will actually cause more problems that it's worth.  If you suspect the salts will help you, check with your doctor or a public health official.
  In many parts of the world, there is concern that people do not get enough iodine, but the salts are too concentrated to help with this.  So, let's take a look at what it does, how much you need, and where to get it.

What Iodine does:  The major roles of the thyroid hormones relate to how the body uses energy; but they also have roles in protein synthesis, brain development, and lipid levels.  It's been known for a long time that if you don't have enough in your diet, you will get a goiter, a type of swelling on the neck.  The thyroid enlarges in an effort to capture every last bit of the iodine in circulation.  Along with this, the person with a goiter feels sluggish and has high cholesterol.  If a pregnant woman is low in iodine, her baby will be affected.  This ranges from mild birth defects to Cretinism, a severe and permanent form of mental retardation.  There is research underway to study how iodine affects fibrocystic breast disease, how it affects diabetes, it's possible function as an antioxidant, and whether it will lower your risk of ulcers, migraines, and some kinds of cancer.

How much Iodine do you need? Current US recommended intake of dietary iodine:
children 1-8 = 90 micrograms/day (no recommendations made for infants)
children 9-13 = 120 mcg
people over 13 years old = 150 mcg
pregnant women  = 220 mcg
lactating women = 290 mcg

Where do you get Iodine? Since 1924, iodized salt has been available in the USA.  One gram salt contains about 60 mcg iodine.  This comes to 360 mcg of iodine per teaspoon of salt.  Use of iodized salt in the years before World War II lead to a significant reduction in goiter, Cretinism, etc.  However, we've recently lost many of those gains.  One reason is that we are cutting down on table salt use due to concerns over hypertension.  (We still get too much sodium, esp. in processed foods, but it is not in the form of iodized salt.)  Some people also use specialty salts in hopes of getting some other trace minerals, or a new flavor experience.
Iodine once was used in bread dough conditioners and in antiseptics at dairies.  These uses have been replaced by other compounds now, so we don't have those incidental sources of iodine in our diets.  Iodine is found in plants and animals grown in the ocean, but for most Americans, this is only a small part of the diet.  Some multi-vitamin/mineral supplements now include iodine, often in doses of 100-150 mg/tablet.
bottom line:  It pays to use iodized salt.  Some supplements may protect you, too.