LOS ANGELES — 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 cofounded 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.
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.
Prescription prenatal vitamins face more stringent government scrutiny than
their supplement counterparts, which do not have to be proven safe before they
are sold.
However, researchers found problems with both types when they tested iodine
levels in 60 prescription and over-the-counter prenatal multivitamins. The
iodine was in the form of kelp or potassium iodide.
In 10 brands, iodine levels were less than half than what was listed on their
labels. Three brands contained iodine levels 50 percent or higher than the
amount advertised. Variations were greater among kelp-containing vitamins.
Based on the study's findings, pregnant women should take prenatal multivitamins
that contain potassium iodide instead of kelp, said Dr. Elizabeth Pearce, one of
the researchers.
