Iodine status of the United States population

Historically iodine deficiency was common in the U.S. in an area referred to as the “goiter belt”. After the introduction of iodized salt in the 1920's iodine deficiency virtually disappeared. The iodine status of the U.S. population has been monitored as part of the the National Health and Nutrition Examination Surveys (NHANES) since the early 1970s. In NHANES I (1971-74), based on median urinary iodine concentration (UIC), there was concern that iodine intake was too high. In subsequent NHANES the median UIC dropped substantially with most population groups having median UICs in the “adequate” range. In the youngest children the iodine status has been “above requirements” while in pregnant women the iodine status has been around the “insufficient iodine intake” level for many years. Based on the low median UIC in pregnant women, the American Thyroid Association, the Endocrine Society, and the Teratology Society recommend daily iodine supplementation for pregnant and lactating women. The primary source of iodine in the U.S. is dairy products. Multivitamins containing iodine are also an important source of iodine. However, not all multivitamins contain iodine, including many prenatal vitamins. Iodized salt contributes a small amount of iodine to the diet but around 50% of adult women rarely or never use table salt and it has been estimated that around 70% of household salt is iodized. Recent data indicate that the iodine status of pregnant women in the U.S. may be insufficient.