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Iodine lacking in prenatal multivitamins

Only 51% of prenatal vitamins in the United States contained iodine.

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The iodine content stated on prenatal vitamin bottle labels was discordant with the measured levels of iodine in the vitamins.

Despite iodine intake recommendations for pregnant and breastfeeding women by the Institute of Medicine, the World Health Organization and the American Thyroid Association, iodine content of prenatal vitamins is not mandated in the United States.

“Because dietary iodine intake is likely to be low among at least a subset of pregnant women in the United States, and iodine intake in pregnancy is critical for fetal neurodevelopment, the ATA has recommended that all pregnant women in the United States and Canada take a daily supplement containing 150 mcg of iodine,” said Elizabeth N. Pearce, MD, MSc, assistant professor of medicine, Boston University School of Medicine.

“The best advice at present for pregnant or lactating women is to read labels carefully and to choose a prenatal vitamin that contains iodine in the form of potassium iodide and not kelp,” she told Endocrine Today.

Iodine needed

Pearce and colleagues identified 114 prenatal multivitamins with labels claiming to contain iodine in the form of kelp (n=42), potassium iodide (n=67) or another ingredient (n=5). They measured the iodine content of 60 randomly selected prenatal multivitamins.

In 35 potassium iodide vitamins, the mean level of iodine per daily dose was 119.0 mcg. According to the researchers, potassium iodide contains 76% iodide; therefore, iodine content was equivalent to 76% of the total potassium iodide content.

There was 33 mcg to 610 mcg of iodine per daily dose in 25 brands of vitamins containing kelp; 13 brands had iodine levels that did not match label values by ≥50% and 10 brands had values lower by ≥50%, according to the study.

“Manufacturers of prenatal multivitamins in the United States should be encouraged to use only potassium iodide to maintain consistency in labeling and to ensure that these vitamins contain 150 mcg of supplemental daily iodine by including at least 197 mcg of potassium iodide per daily dose, as recommended by the ATA,” the researchers wrote. – by Christen Haigh

Leung AM. N Engl J Med. 2009;360:939-940.