THE FULL ARTICLE TITLE:
Patel A et al 2018 Iodine content of the best-selling United States adult and prenatal multivitamin preparations. Thyroid. Epub 2018 Oct 30. PMID: 30266075.
SUMMARY OF THE STUDY
Data for this study was obtained from Information Resources, Inc. (Chicago, IL), a market research firm. It provided information about the 99 US adult and 60 prenatal multivitamins with the largest market share from July 2016 to July 2017. Supplements sold at food, drug, value chains, mass merchandise and military stores were included. However, not included were sales made over the Internet, direct selling and specialty stores. The iodine content and its source was determined using the product labels. Ten products from the adult multivitamin group and one from the prenatal group were excluded because their label was either unavailable or the iodine content could not be determined.
Nearly 74% of the adult multivitamin brands contained iodine, and approximately 75% of these contained 150 mcg per daily dose. The source of the iodine was potassium iodide in all these products. Although some products contained as little as 38 mcgs, none exceeded 150 mcgs per daily dose. Of the prenatal multivitamins, almost 58% of products contained iodine, and 91% contained 150 mcgs per daily dose. The iodine source was potassium iodide in about 75% of the brands, and the sources for the rest was kelp and one brand used inactivated yeast. These last two sources have previously been shown to be variable in their iodine content. Overall, the price of prenatal vitamins is higher than the general adult multivitamin.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Although the majority of the best-selling US brands of adult multivitamins contain iodine, a relatively high proportion (25%) do not. Among the prenatal multivitamins, 40% do not contain iodine. Even though most products contain the recommended amount, there is a wide range in iodine content going from as little as 25 mcgs to 93% higher than the recommended daily dose.
The limitations of this study include the fact that it relied on the manufacturers’ listed iodine content, which may not match the actual content. Also, although using consumer data it was possible to determine how many doses were purchased, it was unclear how many doses were actually consumed, and data from products purchased for example, on the internet was not included.
In summary, multivitamin products appear to be a significant source of iodine nutrition for many US adults. However, in spite of recommendations regarding iodine content in prenatal vitamins, about 40% of the evaluated products do not contain iodine. Therefore, it is extremely important that women, especially when pregnant, breastfeeding or planning a pregnancy, read the labels of their multivitamin supplements to ensure that they are receiving an adequate amount of iodine.