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Mary Shomon

U.S. Population's Iodine Levels Drop, Many Pregnant Women Iodine Deficient

By March 18, 2013

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Iodine -- which is ingested from food and supplements -- is a building block for the production of thyroid hormone. Sufficient iodine is particularly important during early pregnancy, when the brain development of the fetus relies on the mother's intake of iodine and thyroid status.

A new report, using iodine data from the National Health and Nutrition Examination Survey (NHANES), and iodine data from pregnant women at sites around the country, was just published. The study found that the median urinary iodine concentration in 2009-2010 --144 g/L -- was significantly lower than in 2007-2008, which was 164 g/L. Non-Hispanic blacks had the lowest urinary iodine concentrations (131 g/L), compared to non- Hispanic whites or Hispanics (147 and 148 g/L). The median for pregnant women in the 2005-2010 period studied was 129 g/L, which is considered inadequate during pregnancy.

According to the report, the Institute of Medicine's Recommended Dietary Allowance (RDA) for iodine in adult men and women is 150 g per day. (FYI: One teaspoon of iodized table salt contains approximately 400 g iodine.) For pregnant women, the RDA is 220 g iodine per day, and 290 g iodine per day during breastfeeding.

While we often assume that most of our dietary iodine comes from salt, the researchers found that intake of dairy foods -- not salt, seafood or grains -- was significantly and positively associated with urinary iodine levels in women of childbearing age. According to the study:

"Dairy, grain, seafood, and to a lesser degree, iodized salt are the major sources of iodine in the U.S...In the U.S. approximately 60% of iodine consumed comes from dairy products. The iodine is added to dairy products as a consequence of iodine added to cattle feed, or use of iodophor disinfectants in the milking process. Iodized salt accounts for a small amount of dietary iodine. Approximately 70% of salt consumed in the US comes from processed and restaurant foods, which generally do not use iodized salt."
They also concluded that the pregnant women evaluated tended to have inadequate urinary iodine levels during the first and second trimesters of pregnancy. To prevent iodine deficiency, during pregnancy and breastfeeding, the American Thyroid Association recommends that women of childbearing age supplement with 150 g of iodine daily, particularly when planning pregnancy, during pregnancy, and when nursing.

The report concluded: "Prevention of unnecessary self-imposed dairy restriction and improved iodine intake may be achieved by medical evaluation and education of individuals who perceive themselves to be lactose intolerant but who are not. Individuals with confirmed lactose intolerance, particularly women who are pregnant or who are of childbearing age, should be counseled about iodine supplementation. Public health intervention may include continued efforts by the medical community and public health officials to promote the use of iodine- containing prenatal vitamins and to promote continued efforts to monitor actual iodine content in prenatal vitamins."

More on Iodine

  • Guidelines for Iodine Nutrition Before, During and After Pregnancy
  • Iodine in Prenatal Vitamins
  • The Iodine Controversy
  • Thyroid Disorders Linked to Over-the-Counter Iodine Supplements

    Source: Caldwell, KL et. al. "Iodine Status in Pregnant Women in the National Children's Study and in U.S. Women (15-44), NHANES 2005-2010," Thyroid, March, 2013, Instant Online, ahead of print.

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  • Comments
    March 19, 2013 at 9:42 am
    (1) Donnie says:

    Those of us who are allergic to corn, can not get iodine from iodized salt, because It contains a corn-derived additive. We have to use non-iodized salt, to avoid allergic reactions from corn. I suspect that a lot of corn allergic people are deficient in iodine, if they don’t use a supplement that contains it. Especially, since many dairy products contain corn-derived additives, too.

    March 19, 2013 at 10:52 pm
    (2) Dick Hanneman says:

    So, Mary Shomon, what’s the name of this report? When was it published? In what journal? etc. Help us readers, please.

    March 20, 2013 at 5:46 pm
    (3) Jennifer says:

    Ditto on above comment. I’d like to read that report. The conclusion that people should eat more dairy to get their iodine quota seems patently ridiculous.

    Why depend upon some mass produced product that was inadvertently soaked with iodine due to the feed and disinfection processes. Who knows when those will be changed anyway?

    If we need to supplement iodine why don’t we just do that ourselves? Lugol’s and Iodoral are readily available.

    March 23, 2013 at 9:57 pm
    (4) rachel says:

    SEAWEED, y’all….
    Plain old nori (like around sushi) or the stuff floating in Miso soup, or any yummy sea vegetable…
    Certainly any that say “aquamin” or “sea minerals” or “seaweed”

    How do I know? I am HyPERthyroid and have to limit my intake of all of these.
    Go figure.
    Also: most multivitamins and many blends (like cal-mag) happen to have iodine.

    March 25, 2013 at 8:23 pm
    (5) tammy says:

    I don’t know how many iodine enriched products ther are, but soy with iodine is useless for the iodine purpose as soy blocks iodine from getting to the cells. That’s like eating tums for the calcium, as antacids block calcium. But what a way to sell a product!

    March 26, 2013 at 10:07 am
    (6) Cara says:

    In the case of milk unless you’re using supplemented milk – with added vit A + D and / or added calcium, then your milk certainly shouldn’t contain any corn derivatives at all. With fruit yogurt, it may contain HCFS and certain flavoured cheeses may have corn derivatives tho’..
    The problem with supplementing with iodine by oneself is that this can be very risky for some hashi’s patients and can cause extreme side effects, so for some should only be done with the assistance of a healthcare professional.
    As for calcium enriched soya milks??? As soya absolutely CONTRA-INDICATED for the vast majority of those with Hashi’s this is absolutely NOT a good idea.

    March 26, 2013 at 7:51 pm
    (7) jackie says:

    Dr. David Brownstein (author of the book, Iodine, why you need it, why you can’t live without it) is an expert on the subject. Iodine and potassium iodide together are what the body uses. One or the other separately can cause a problem. Iodine is an essential element necessary to human health. There are also companion nutrients that should be taken, and anyone taking iodine should read up first. I am using iodine therapy myself. It is important to realize that iodine has a strong detoxifying affect on the body, pulling out heavy earth metals and hallides that don’t belong in the body, such as flouride toxicity, bromide, mercury, etc. Detox reactions can be severe. It’s not the iodine, it is the detoxifying affects of the iodine. Asians consume an average of 12.5 mg of iodine daily in their diets. The USDA recommendation is 150 IU. I’m thinking there is a descrepancy there somewhere. Supplemental levels of iodine in the 30′s in the United States were much higher than the recommended amount now. And once again, people are having health problems due to iodine deficiency, much of which is due to environmental toxins, in our food, our water, in the air, in the mattresses we lie on, in the plastic bottles that we drink out of, etc…

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