Iodine Nutrition in the United States. Trends and Public Health Implications

JG Hollowell, et al (CDC), "Iodine Nutrition in the United States. Trends and Public Health Implications: Iodine Excretion Data from National Health and Nutrition Examination Surveys I and III (1971–1974 and 1988–1994)", Journal of Clinical Endocrinology and Metabolism, October 1998.

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Conclusion:

Clearly, the iodine intake in the United States has decreased over the past 20 yr. Awareness of a possible continuing decline in iodine intake in this population can be achieved by monitoring the food supply, especially the intake of iodine in women of child-bearing age. This monitoring can be performed by continuing the measurement of iodine in the Total Diet Study and by including UI in the next NHANES survey, which is about to begin. Surveillance of thyroid diseases should be emphasized, but we should not wait for the prevalence of goiter to increase or for changes in thyroid disease patterns to occur due to decreased iodine intake. Should surveillance indicate a further decrease in iodine intake, measures may be required to increase the amount of iodine consumed by the U.S. population to prevent the possibility of the reemergence of iodine deficiency in the United States.

Nine years later, Dr. Hollowell and a collegue published "The prevalence of iodine deficiency in women
of reproductive age in the United States of America" in Public Health Nutriition, October 2007.  Read it here.

Conclusion:

When a subgroup, such as women of reproductive age, is demonstrated to be affected by moderate or severe iodine deficiency, immediate remedies would be indicated for the entire population. The data at hand do not support the conclusion that the group of pregnant women, or any other group in the USA, is deficient in iodine.  The WHO thresholds are based on UI concentrations correlated with goitre rates in school children. These measurements have been used to estimate the adequacy of iodine nutrition in children and then generalised to estimate the iodine status of the population. The time has come to establish similar guidelines and criteria for other age groups or biological states, such as pregnancy. These criteria should be derived by relating the UI concentration of each subgroup with physiological outcomes, such as the goitre rate, the serum thyroglobulin concentration or, perhaps some other sensitive biological outcome. Until this is done, the estimated risk for the subgroup being studied may not be understood and could be inaccurate. Until such research is completed, we support the use of iodine supplements by all pregnant women because of the potential harm of iodine deficiency during pregnancy.