Research needs for assessing iodine intake, iodine status, and the effects of maternal iodine supplementation

Abstract

The Office of Dietary Supplements of the NIH convened 3 workshops on iodine nutrition in Rockville, Maryland, in 2014. The purpose of the current article is to summarize and briefly discuss a list of research and resource needs developed with the input of workshop participants. This list is composed of the basic, clinical, translational, and population studies required for characterizing the benefits and risks of iodine supplementation, along with related data, analyses, evaluations, methods development, and supporting activities. Ancillary studies designed to use the participant, biological sample, and data resources of ongoing and completed studies (including those not originally concerned with iodine) may provide an efficient, cost-effective means to address some of these research and resource needs. In the United States, the foremost question is whether neurobehavioral development in the offspring of mildly to moderately iodine-deficient women is improved by maternal iodine supplementation during pregnancy. It is important to identify the benefits and risks of iodine supplementation in all population subgroups so that supplementation can be targeted, if necessary, to avoid increasing the risk of thyroid dysfunction and related adverse health effects in those with high iodine intakes. Ultimately, there will be a need for well-designed trials and other studies to assess the impact of maternal supplementation on neurodevelopmental outcomes in the offspring. However, 2 basic information gaps loom ahead of such a study: the development of robust, valid, and convenient biomarkers of individual iodine status and the identification of infant and toddler neurobehavioral development endpoints that are sensitive to mild maternal iodine deficiency during pregnancy and its reversal by supplementation.

A Role for Iodide and Thyroglobulin in Modulating the Function of Human Immune Cells

“…This is observed in persons with sufficient iodine levels where typically an iodine urinary loading test shows excretion of 90% or more of the ingested iodine within 24 h and much less in iodine deficient populations ( 71 , 72 ). In fact, studies focusing on assessment of long-term levels of iodine status suggest biomarkers such as TG or urinary iodine as the more sensitive markers for iodine levels ( 50 – 52 , 73 , 74 ). Ingested iodine is therefore either rapidly absorbed by the thyroid and tissues expressing iodine transporters that are widely distributed or is excreted by the urine in quantities inversely correlated with whole-body sufficiency ( 28 , 69 , 72 ).…”

New Iodine Food Composition Database and Updated Calculations of Iodine Intake among Norwegians

“…In addition, changes in the environment in which fish live and in the processing of fish, changes in soil, use of fertilizers, changes in the composition and fortification of cattle and chicken fodder, and use of iodized salt in food processing, all influence the total iodine content in our diets [ 14 , 15 , 16 ]. Furthermore, changes in food habits may influence the dietary intake of iodine and individuals whose diets exclude or restrict iodine-rich food sources, for health, religious, or other reasons are at a special risk of deficiency [ 17 ].…”

The joint role of thyroid function and iodine concentration on gestational diabetes risk in a population‐based study

“…The most common sources of iodine in the Finnish diet are from dairy products (from voluntarily fortified feed) and iodized salt; however, consumption of both dairy and salt in the country has declined over the past decade . Characterization of the potential risks of mild iodine deficiency is also crucial for estimating possible health gains from improved iodine supplementation policies . While numerous studies have examined the effects of iodine deficiency on birth outcomes in offspring, few studies have explored associations between mild iodine deficiency, its relation with thyroid function, and GDM.…”