In the developing baby, iodine is necessary for thyroid function and normal brain development. According to a recent Lancet study, even children born to women with mild-to-moderate iodine deficiency during pregnancy are at increased risk for lower IQ and reading ability (assessed at age 9). The most severe effects were observed among children born to women with severe deficiency.
To reduce the risk of iodine deficiency, iodine was added to table salt. Nowadays, however, most salt consumed by Americans comes from processed foods which is prepared with salt that is not iodized. In addition, sea salt and kosher salt are used more commonly now; neither of these contains iodine. At greatest risk for iodine deficiency are women who are vegan (and others who do not consume dairy and fish). It turns out that many American women may be marginally iodine deficient, and studies estimate that only 15 to 20 percent of pregnant and nursing women are taking supplements containing iodine. Many women may thus need iodine supplementation.
Unfortunately, not all prenatal vitamins contain adequate amounts of iodine; you need to read the label carefully. It is recommended that pregnant and breastfeeding women should take a supplement that includes at least 150 micrograms of iodide, and should use iodized table salt. The US recommended daily allowances (RDA) for iodine intake are 150 mcg in adults, 220 to 250 mcg in pregnant women, and 250 to 290 mcg in breastfeeding women.
Last year the American Academy of Pediatrics released a policy statement that all pregnant and breast-feeding women should take a vitamin supplement with adequate iodide. The American Thyroid Association (ATA) and other groups are now lobbying for the inclusion of the iodine prenatal vitamin supplement recommendation into the 2015 Dietary Guidelines for Americans.
There is, however, an upper safety limit for iodine supplementation. Taking more than 1100 mcg per day is not recommended because this increases the risk for thyroid dysfunction, particularly in pregnant and lactating women. It is important to read the label carefully; it should be noted that many iodine and kelp supplements contain levels of iodine that are much higher than the daily recommended allowance.
Ruta Nonacs, MD PhD
Iodine Needs in the Pregnant and Postpartum Woman (American Thyroid Association)
Policy Statement: Iodine Deficiency, Pollutant Chemicals, and the Thyroid: New Information on an Old Problem. Pediatrics. 2014; 133:1163-1166.
Leung AM, Avram AM, Brenner AV, et al. Potential risks of excess iodine ingestion and exposure: statement by the american thyroid association public health committee. Thyroid. 2015 Feb; 25(2):145-6.