Selenium and iodine: essential trace elements for the thyroid

Peer-reviewed / Manuscript (overview) received: November 09, 2018 / Revision accepted: March 14, 2019

Introduction

Selenium and iodine are among the essential trace elements. Ensuring a comprehensive, adequate supply of these elements remains a challenge across the globe to this day, despite extensive efforts (such as the iodination of table salt). Factors that play a decisive role in the supply of these nutrients include not only soil conditions and traditional foods, but also the increasing spread of dietary trends, particularly in Europe.

A recently published study recorded the nutrient intakes of 32,423 study participants (EPIC- Oxford cohort) using diet questionnaires adapted to the participants’ eating habits [1]. Both, this study and similar studies conducted in Germany showed that vegetarians had a lower selenium intake than people who consume meat and fish. Vegans are particularly at risk of inadequate iodine intake (exception: those who consume seaweed) [2]. The same conclusion was drawn by studies that used biomarkers to determine the status of both of these trace elements [3, 4].

In addition to diet, another cause of inadequate supply of trace elements are diseases such as inflammatory bowel disease or renal insufficiency, which can cause changes in the uptake or excretion of trace elements, respectively.

Abstract

Selenium and iodine are essential trace elements that work together to ensure that the thyroid functions optimally. A deficiency in one or both of these elements leads to fluctuations in thyroid hormone production, which have far-reaching consequences in terms of metabolic processes, neurological development, and disease. Iodine and selenium supply also play an important role in autoimmune diseases of the thyroid. Both the total selenium concentration in the serum and the concentration of selenoprotein P are suitable biomarkers for determining selenium status. Iodine concentration in the urine is the most commonly used method of determining iodine status. In order to improve assessment of supply status for these two essential trace elements plus an additional four, the TraceAge research group is identifying age- and sex-specific trace element profiles as well as new functional biomarkers for the individual trace elements. In addition, the research group will investigate interactions with other trace elements in more detail.

Keywords: selenium, iodine, thyroid gland, autoimmune diseases of the thyroid, selenoproteins, TraceAge

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