New Recommendations Call for Iodine in All Prenatal Vitamins

Miriam E Tucker

February 19, 2015

Endocrinology groups are applauding a new recommendation from a dietary-supplement trade association that calls for iodine supplementation in all prenatal vitamins prescribed for pregnant and breastfeeding women.

In addition, the public health committee of the American Thyroid Association (ATA) recently published a statement reiterating the ATA recommendation that women take a daily multivitamin containing 150 μg of iodine during prepregnancy, pregnancy, and lactation. The statement also warns of the potential risks of excess iodine consumption and exposure, particularly through the use of unregulated kelp supplements.

The US Council for Responsible Nutrition's new guidelines call for all dietary-supplement manufacturers and marketers to begin including at least 150 μg of iodine in all daily multivitamin/mineral supplements intended for pregnant and lactating women in the United States within the next 12 months.

The ATA had lobbied for the move, in conjunction with the Endocrine Society, the American Association of Clinical Endocrinologists, the Iodine Global Network, and the Teratology Society.

"A number of organizations have been trying to get iodine in prenatal vitamins," endocrinologist Alex Stagnaro-Green, MD, from the University of Illinois College of Medicine, Rockford, and chair of the ATA task force on thyroid disease during pregnancy and postpartum, told Medscape Medical News. "This is a huge win for public health, from my perspective and the perspective of the ATA."

In the past several years, removal of iodized salt from commercial products such as bread and milk, along with increased use of kosher salt and sea salt, which don't contain iodine, and the adoption of vegetarian and vegan diets have led to a reduction in dietary iodine consumption. "There never was a coherent US policy about iodization," Dr Stagnaro-Green noted.

Worldwide, about two billion people are iodine-deficient. While most of the US population has adequate iodine levels, data from the National Health and Nutrition Examination Survey suggest that more than half of pregnant women have urinary iodine concentrations below 150 mg/dL (Thyroid. 2011;21:419-427).

Pregnant women actually need more iodine than other people because of increased thyroid-hormone production, renal losses, and fetal iodine requirements. Iodine deficiency during pregnancy can result in maternal and fetal goiter, cretinism, intellectual impairment, neonatal hypothyroidism, and increased pregnancy loss and mortality, Dr Stagnaro-Green and colleagues explained in a 2012 editorial (JAMA 2012;308:2463-2464).

"So, women of childbearing age are the subpopulation of Americans with the lowest iodine levels yet have the greatest need during pregnancy and breastfeeding, for the neurodevelopment of the fetal and neonatal brain," he told Medscape Medical News.

In 2009, a study found that only 51% of US prenatal multivitamin brands contained any iodine and, in a number of randomly selected brands, the actual dose of iodine contained in the supplements did not match values on the labeling.

When asked about this new recommendation from the trade association, Dr Stagnaro-Green said, "I would classify it as a triumph."

Now, the ATA and the other groups are lobbying for placement of the iodine prenatal vitamin supplement recommendation into the upcoming Dietary Guidelines for Americans.

However, the American College of Obstetricians and Gynecologists (ACOG) has not joined in these efforts. While the group does recommend the 150-μg dose for pregnant and lactating women, it does not currently endorse the prenatal-supplement recommendation, advising instead that women get their iodine through dietary sources.

Scott Sullivan, MD, from the Medical University of South Carolina, Charleston, who has worked with ACOG on this issue, told Medscape Medical News , "Prenatal iodine supplementation has been under discussion at ACOG and [the Society for Maternal-Fetal Medicine] for some time. No one questions the fact that American women have a risk for iodine deficiency, some in the severe range. What is lacking is a randomized controlled trial that demonstrates improved maternal, fetal, or neonatal outcome with universal iodine supplementation. ACOG usually will not endorse a recommendation until those data are available."

However, he added, "I personally have been a signatory to both the Endocrine Society and the American Thyroid Association guidelines, which both recommend universal iodine supplementation, ideally through prenatal vitamins, in pregnancy. I do this with my personal patients and recommend it when consulted. I believe that as data continue to come in, this will be proven to be a winning strategy for pregnant women."

But Don't Overdo It

In the ATA's public health committee statement, Angela M Leung, MD, from the University of California Los Angeles David Geffen School of Medicine, and colleagues, including Dr Stagnaro-Green, note that iodine is a micronutrient required for normal thyroid function. The US recommended daily allowances (RDA) for iodine intake are 150 μg in adults, 220 to 250 μg in pregnant women, and 250 to 290 μg in breastfeeding women. Dietary sources such as iodized salt, dairy products, some breads, and seafood usually contain enough to meet the RDA for most people who aren't pregnant or lactating.

However, there is an upper safety limit, with ingestion of more than 1100 μg/day not recommended due to the risk for thyroid dysfunction. In particular, infants, the elderly, pregnant and lactating women, and people with preexisting thyroid disease are at risk for adverse effects of excess iodine on the thyroid.

Many iodine, potassium iodide, and kelp supplements contain hundredfold greater amounts of iodine than the recommended upper limit, Dr Leung and colleagues caution.

"Given the increasing popularity of iodine and kelp supplements, recommendations cautioning against excess iodine were indicated. The potential result of iodine-induced thyroid dysfunction, which may be particularly harmful during pregnancy and breastfeeding and in the elderly, may not be well-known," she told Medscape Medical News.

There are a few specific clinical scenarios in which the short-term use of high-dose iodine is indicated, such as for the treatment of thyroid storm, prior to surgery for Graves' disease, for individuals living in the vicinity of a nuclear power plant to be used in the event of an accident, and for patients who need to receive iodinated contrast dyes for radiologic studies.

In such instances, patients should be monitored for iodine-induced thyroid dysfunction, Dr Leung and colleagues advise.

Referring to both of the ATA recent statements, she told Medscape Medical News, "We hope that these two recent articles highlight the critical importance of the appropriate amount of iodine intake, particularly among pregnant and breastfeeding women in whom there may be adverse effects to the developing fetus and newborn infant with both iodine deficiency and iodine excess."

Dr Leung and colleagues report no relevant financial relationships, as do Dr Stagnaro-Green and Dr Sullivan.

Thyroid. 2015;25:145-146. Abstract

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