By Margarita Nahapetyan
Most prenatal multivitamins marketed in the United States, do not contain all the iodine they state on the label, potentially posing infants at risk of poor brain development, researchers reported earlier this week. A new study found that only 51 per cent of all prenatal vitamin brands contained any iodine in spite of the fact that the chemical element is critical for neuro-cognitive development.
Using the Internet, doctors at Boston University Medical Center examined 223 brands of prenatal multivitamins available in the United States at present moment, 127 prescription and 96 nonprescription brands. Only about half of them - 114 - listed iodine on their labels: 87 of the nonprescription and 27 of the prescription brands. According to the labeling, 101 (89 per cent) of these products contained at least 150 micrograms of iodine in a daily dose.
Prescription prenatal multivitamins face more strict government scrutiny than vitamins sold over-the-counter, which do not have to be proven safe before being put out to market. However, problems have been found with both types when iodine levels were tested in 60 prescription and over-the-counter prenatal vitamin supplements. Sixty-seven vitamins contained iodine from potassium iodide, 42 from kelp, and five from some other source.
Tests showed that of all vitamins with potassium iodide, the average level of iodine was 119 mcg per daily dose, which is less than the recommended dosage. Among vitamins containing kelp, the iodine levels ranged from 33 to 610 mcg per daily dose. Scientists say that taking too much iodine can result in problems, especially for women with a thyroid problem. In more than 10 brands, the actual iodine levels were less than half than what was being advertised on their labels, and three brands had iodine levels at least 50 per cent higher from what was stated on the labeling. Variations were greater among kelp-containing vitamins.
"Iodine nutrition is critically important in pregnancy," stated Dr. Elizabeth Pearce, a co-author of the study and an assistant professor of medicine at Boston University Medical Center. "Women who are deficient in pregnancy have children often with lower IQs or neuro-cognitive delays. Deficiency in iodine is the leading cause of preventable mental retardation in the world."
However, according to new findings, "it seems that an ideal prenatal vitamin, in terms of iodine, does not exist," she said. "Almost half of them have iodine that is being derived from kelp and that is very variable."
Iodine is an essential chemical element that makes it possible for thyroid gland to produce thyroid hormones. Iodine deficiency is a leading cause of preventable mental retardation affecting more than two billion people all around the world. Iodine is commonly added to table salt and can be found in seafood, dairy products and bread.
The American Thyroid Association recommends that pregnant and nursing women take a daily dose of prenatal multivitamins containing 150 micrograms of iodine, which is necessary for proper thyroid function. During pregnancy, women who do not have sufficient levels of thyroid hormones, put their babies, besides of the risk of mental retardation and growth, also to the higher risk of hearing and speech problems.
A letter appears in the Feb. 26, 2009 issue of the New England Journal of Medicine.