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The Iodine Controversy

Too Much vs. Not Enough, and What It Does To Your Thyroid?


Updated June 02, 2014

An Important Note: The researchers were defining overt hypothyroidism as a TSH above 4.8, with elevated Free T4 levels. Subclinical hypothyroidism was defined as a TSH above 4.8, with normal range Free T4 levels. The American Association of Clinical Endocrinologists, along with the National Academy of Clinical Biochemistry, recommended in late 2002/early 2003 that the TSH normal range be narrowed substantially to .3 to 3.0. So the point at which someone would be considered overtly hypothyroid might be different, based on these new guidelines.

Do You Need Iodine?

Many decades ago, iodization of salt was voluntarily instituted in the U.S. and other industrialized countries as a means to counteract iodine deficiency. In these areas with iodized salt, iodine deficiency disorders were all but eliminated, and most Americans do have sufficient iodine.

During the past two decades, however, reductions in salt intake for health reasons, reduced use of iodized salt in processed foods, and the fact that iodization is not mandatory in the U.S. (even then, some 70% of table salt is iodized) have resulted in a cutback in iodine intake even in countries like the U.S. So after a period where iodine deficiency in the U.S. had been all but eliminated, it is now on a slow by steady upward rise.

The greatest concern is in pregnancy women. In fact, the rate of pregnant women with iodine deficiency has increased in the U.S. over the past 20 years Utiger, from just 1 percent in the 1970s to 7 percent in 2002. These women and their babies face the greatest risks from insufficient iodine in their diet.

Some experts recommend that iodine supplementation be standard during pre-conception and pregnancy. The recommended dietary allowance for iodine is 200 mcg/day during pregnancy and 75 mcg/day while breastfeeding.

For the rest of us, the answer for optimum thyroid health is, therefore, to get enough -- but not too much -- iodine. You might be deficient in iodine if you have, for health reasons, cut iodized salt out of your diet, or switched to non-iodized sea salt.

So, do you need supplemental iodine? How can you tell for sure if you are getting enough iodine? It's almost impossible to gauge on your own. You can do an very rough estimate, however, based on the following questions:

  • Do you use iodized salt?
  • How much salt do you eat daily?
  • Do you take a vitamin or supplement with iodine? (How much iodine is in the supplement?)
  • Do you eat, meat, dairy products or seafood regularly?
Some alternative, holistic and herbal practitioners are almost knee-jerk in their insistence that anyone with a thyroid problem requires iodine supplementation (either liquid iodine, or an herb that contains iodine, such as kelp or bladderwrack). This can aggravate symptoms and worse thyroid problems in some people. (See my own story of iodine problems.)

But, unless you are planning to get pregnant, are currently pregnant or you're breastfeeding, you'll want to be very careful about taking iodine unless you and your practitioner have some very strong evidence that you are deficient. If your practitioner recommends iodine supplementation as a thyroid treatment, you may wish to ask for a more specific test that can measure iodine levels -- the "urinary excretion" test. This test which evaluates the iodine excreted in the urine, and gives an indirect but fairly accurate assessment of iodine levels, and can document deficiency.

Also, watch out for the so-called "thyroid support" vitamin and supplement formulas, including the heavily marketed and promoted Alvidar. Most, like Alvidar, include substantial amounts of iodine, and if you are not iodine-deficient, they can end up having the unintended and opposite effect of actually making your symptoms worse, and aggravating your thyroid condition.


Teng, Weiping M.D., et. al. "Effect of Iodine Intake on Thyroid Diseases in China" New England Journal of Medicine, Volume 354:2783-2793, June 29, 2006, Number 26 Abstract

Utiger, Robert D. M.D. "Iodine Nutrition - More Is Better," New England Journal of Medicine, Volume 354:2819-2821, June 29, 2006, Number 26

Higdon, Jane Ph.D. et. al. "Iodine," Micronutrient Information Center, Linus Pauling Insitute, Oregon State University, 2003 Article

International Council for the Control of Iodine Deficiency Disorders

Shomon, Mary J. The Thyroid Guide to Fertility, Pregnancy and Breastfeeding Success, Thyroid-Info, 2006

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