Study: Some Prenatal Vitamins Lack Enough Iodine

Many brands of multivitamins for pregnant women may not contain all the iodine they claim, potentially putting babies at risk of poor brain development, a new study suggests.

Tests on 60 brands that listed iodine as an ingredient on their labels found many fell short of the stated amount. The risk of too little iodine appears greater with "natural" vitamins that get their iodine from kelp rather than a salt form, the study found.

"If these numbers are all real, then they're not meeting their label claim and that's a problem," said William Obermeyer, a former Food and Drug Administration scientist who co-founded ConsumerLab.com, a private testing service. Obermeyer was not part of the research.

The study was done by scientists at the Boston University Iodine Research Laboratory. Results were reported in a letter published in Thursday's New England Journal of Medicine. No brands were named in the analysis.

Iodine is commonly added to table salt and can be found in seafood, dairy products and bread. Iodine deficiency affects more than 2 billion people worldwide and is the leading cause of mental retardation.

Pregnant and nursing women need 220 to 290 micrograms of iodine a day, according to the Institute of Medicine. Expecting mothers who don't get enough can put their babies at greater risk of mental retardation and growth, hearing and speech problems.

The American Thyroid Association recommends that pregnant women take a daily dose of prenatal multivitamins containing 150 micrograms of iodine, which is needed for proper thyroid function. During pregnancy, having enough thyroid hormones is important for fetal brain development.

There is no law requiring vitamin makers to add iodine to prenatal multivitamins, which are available by prescription or bought over-the-counter as dietary supplements.

Boston University scientists last year looked at 223 prenatal multivitamins available by prescription or sold over-the-counter in the United States. About half of them — 114 — listed iodine on their labels.