A growing number of pregnant and nursing women in the U.S. have iodine deficiencies, according to a group of experts who wrote an opinion paper published Tuesday in the Journal of the American Medical Association calling for potassium iodide to be included in all prenatal vitamins.
Iodine deficiency causes low thyroid hormone levels in mothers and can lead to brain development disorders in babies.
Iodine is most commonly found in dairy products, seafood, and breads. Since it is not a naturally made chemical in the body, women must rely on an iodine-rich diet to get the recommended amount.
Only 20 percent of prenatal vitamins available contain potassium iodide, according to Dr. Alex Stagnaro-Green, professor of obstetrics and gynecology at the George Washington University School of Medicine and Health Sciences and lead author of the paper.
Potassium iodide contains 76 percent iodine and is considered the most stable source of iodine.
The American College of Obstetricians and Gynecology (ACOG), following recommendations by the World Health Organization, considers normal levels of iodine to be between 150 to 250 micrograms per liter.
Stagnaro and his colleagues used the U.S. Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey to track women’s iodine levels over more than a decade.
Iodine levels among women living in the U.S. have steadily decreased, according to the paper. Between 2001 and 2006, the average level of iodine among pregnant women was 150 micrograms, the lowest threshold for normal levels. Between 2007 and 2008, the median level among pregnant women was 129 micrograms per liter.
“The group with the lowest level is young women of childbearing age,” said Stagnaro-Green. “It’s the group where it’s most important that they have it.”
Because iodine levels are difficult to test in individual women and are not usually done during prenatal visits, it’s difficult to tell what type of women may be at risk for iodine deficiency.
However, according to Dr. Elizabeth Pearce, associate professor of medicine at Boston University’s School of Medicine and co-author of the paper, women who are vegan may be highest risk for iodine deficiency.
“We know that adequate iodine levels are the only preventable cause of mental retardation,” said Pearce. “We can’t diagnose iodine levels individually in women, and that’s the problem.”
However, experts said that adding 150 micrograms of potassium iodide to prenatal vitamins may be beneficial for all women to help them produce more thyroid hormone.
"The tone here is to optimize outcomes, not to cause panic,” said Dr. Jeffrey Ecker, a high-risk obstetrician at Massachusetts General Hospital and vice chair of ACOG’s committee on obstetrics practices. Ecker was not among the experts involved in the published opinion paper.
Iodine deficiency among pregnant and nursing women is not as prevalent in the U.S. as it is in other countries, Ecker said.
“Many women will already have sufficient amounts of iodine and those that don’t would only have a mild deficiency,” said Ecker. “It’s not something that crossed my mind before, but now that it has, it’s hard not to agree with the recommended conclusion.”
Prolonged and high doses of iodine – often exceeding 900 micrograms -- can cause thyroid problems. But experts agreed that the recommended amount is not enough to bring on negative side effects.
The U.S. Institute of Medicine recommends 220 micrograms of iodine per day for pregnant women, and 290 micrograms per day for women who are breastfeeding.
“With the increased level needed, I’m hard pressed to see where 150 micrograms is going to put someone at excess,” he said.
However, experts agreed that women should not go looking for potassium iodide supplements if it is not already included in their prenatal vitamins.
Consuming iodized salt, rather than kosher or sea salt, and drinking more milk are some ways to increase iodine intake naturally.
“Just because you’re taking vitamins without iodine in it, it shouldn’t cause concern or an immediate need to switch,” said Ecker, who recommended consulting a doctor first.
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