Shaky Amount of Iodine in U.S. Salt

Some 'Iodine-Fortified' Table Salt Falls Short of Recommended Levels of the Nutrient, Study Shows

Medically Reviewed by Louise Chang, MD on February 01, 2008

Feb. 1, 2008 -- There are fewer food sources of iodine in the American dietthan there were just a few decades ago, raising the risk of iodine deficiencyin a growing number of people. So says a researcher who calls himself an"iodine activist."

Even people who buy and use iodine-fortified table salt may be at risk, saysPurnendu K. Dasgupta, PhD, a chemistry professor at the University of Texas atArlington.

Dasgupta and colleagues recently tested 88 samples of iodized salt and foundthat 47 of them, or 53%, did not meet the U.S. Food and Drug Administration'srecommendations for iodine levels.

Iodine levels tended to decrease in individual containers with exposure tohumidity, but light and heat had little effect.

The findings are published in the latest online issue of the AmericanChemical Society journal Environmental Science and Technology.

"We certainly are not saying that people need to eat more salt,"Dasgupta says. "But if we had mandatory iodization of all salt used infood, that would solve the problem."

Most Salt Has No Iodine

Iodized salt is now the main source of iodine in the American diet, but onlyabout 20% of the salt Americans eat contains the micronutrient, Dasguptasays.

Increasing popular "designer" table salts, such as sea salts andKosher salts, usually do not have iodine, and neither does salt used in mostfast foods and processed foods.

Add to this the fact that iodine is no longer used in the production ofcommercial breads and dairy products, plus the ever-present public healthwarnings about restricting dietary salt, and iodine deficiency becomes a realthreat for some people in the United States, Dasgupta says.

Though government nutrition surveys suggest that iodine deficiency is not aproblem in the United States at the population level, Dasgupta says this maynot be the case for the most vulnerable subgroups: pregnant and nursing women,babies, and young children.

Iodine is important in the production of thyroid hormones and critical to normal braindevelopment in newborn infants and children. Iodine deficiency is the leadingpreventable cause of cretinism in the developing world. And at least one studysuggests that children in developed countries born to iodine-deficient moms mayhave an increased risk of attention deficit hyperactivity disorder (ADHD).

Pregnant Women Need Iodine

Boston University Medical Center endocrinologist Elizabeth Pearce, MD, tellsWebMD her research suggests that about half of pregnant and nursing women arenot getting enough iodine in their diets.

In her latest study, published last May, sampled breast milk from 47% ofnursing mothers did not contain sufficient iodine to meet their infants'nutritional needs.

One problem, she says, is that only about a third of over-the-countervitamins recommended for pregnant and nursing women and two-thirds ofprescription prenatalvitamins contain iodine.

In 2006, the American Thyroid Association published guidelines recommendingthat all pregnant and breastfeeding women take prenatal vitamins containingiodine, but Pearce says few women have likely heard about therecommendation.

"It is very difficult to measure iodine deficiency in individuals,"she says. "Because of this, and because pregnant and breastfeeding womenare particularly vulnerable, these women should make sure that they take avitamin with iodine."

Show Sources


Dasgupta, P.K., Environmental Science and Technology, Feb. 15, 2008; online edition.

Purnendu K. Dasgupta, PhD, professor and chairman, department of chemistry, The University of Texas at Arlington.

Elizabeth N. Pearce, MD, assistant professor of medicine, Boston University School of Medicine.

Journal of Clinical Endocrinology and Metabolism, 2004.

ATA Iodine Supplementation for Pregnancy and Lactation, Thyroid, 2006; vol. 16.

Journal of Clinical Endocrinology and Metabolism, May 2007.

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