Iodine Status and Thyroid Function in a Group of Seaweed Consumers in Norway.

Inger Aakre,Lise Madsen,Marian Kjellevold,Lidunn Tveito Evensen,Jan Alexander,Lisbeth Dahl,Maria Wik Markhus,Sigrun Henjum

doi:10.3390/nu12113483

Abstract

Seaweeds, or macroalgae, may be a good dietary iodine source but also a source of excessive iodine intake. The main aim in this study was to describe the iodine status and thyroid function in a group of macroalgae consumers. Two urine samples were collected from each participant (n = 44) to measure urinary iodine concentration (UIC) after habitual consumption of seaweed. Serum thyroid stimulating hormone (TSH), free thyroxine (fT4), free triiodothyronine (fT3), and peroxidase autoantibody (TPOAb), were measured in a subgroup (n = 19). A food frequency questionnaire and an iodine-specific 24 h recall were used to assess iodine intake and macroalgae consumption. The median (p25–p75) UIC was 1200 (370–2850) μg/L. Median (p25–p75) estimated dietary iodine intake, excluding macroalgae, was 110 (78–680) μg/day, indicating that seaweed was the major contributor to the iodine intake. TSH levels were within the reference values, but higher than in other comparable population groups. One third of the participants used seaweeds daily, and sugar kelp, winged kelp, dulse and laver were the most common species. Labelling of iodine content was lacking for a large share of the products consumed. This study found excessive iodine status in macroalgae consumers after intake of dietary seaweeds. Including macroalgae in the diet may give excessive iodine exposure, and consumers should be made aware of the risk associated with inclusion of macroalgae in their diet.

Highlights

Iodine is an essential micronutrient required for the synthesis of thyroid hormones [1]
urinary iodine concentration (UIC) measured 3–4 and 7–8 h after ingestion of macroalgae is presented in Table 2, together with habitual and 24 h iodine intake
It is considered a strength that we have two urine samples per participant, it must be noted that UIC from this study provides information about the iodine status after macroalgae consumption

Summary

Introduction

Iodine is an essential micronutrient required for the synthesis of thyroid hormones [1]. It is found in few foods of terrestrial origin [2], in countries where fodder is enriched with iodine, milk, dairy products and eggs may be good dietary sources [3,4]. Marine foods, such as fish and shellfish are naturally high in iodine due to the high iodine concentration in seawater [2]. Macroalgae has entered the global food market, and has become increasingly popular in the western part of the world [12,13]

Objectives

Methods

Results

Discussion

Conclusion