Insufficient iodine status in pregnant women as a consequence of dietary changes.

Solveig Adalsteinsdottir,Petra Arohonka,Bryndis Eva Birgisdottir,Ellen Alma Tryggvadottir,Ingibjorg Gunnarsdottir,Iris Erlund,Ingibjorg Th Hreidarsdottir,Laufey Hrolfsdottir,Hildur Hardardottir,Thorhallur I Halldorsson

doi:10.29219/fnr.v64.3653

Abstract

BackgroundHistorically, Iceland has been an iodine-sufficient nation due to notably high fish and milk consumption. Recent data suggest that the intake of these important dietary sources of iodine has decreased considerably.ObjectiveTo evaluate the iodine status of pregnant women in Iceland and to determine dietary factors associated with risk for deficiency.MethodsSubjects were women (n = 983; 73% of the eligible sample) attending their first ultrasound appointment in gestational weeks 11–14 in the period October 2017–March 2018. Spot urine samples were collected for assessment of urinary iodine concentration (UIC) and creatinine. The ratio of iodine to creatinine (I/Cr) was calculated. Median UIC was compared with the optimal range of 150–249 μg/L defined by the World Health Organization (WHO). Diet was assessed using a semiquantitative food frequency questionnaire (FFQ), which provided information on main dietary sources of iodine in the population studied (dairy and fish).ResultsThe median UIC (95% confidence interval (CI)) and I/Cr of the study population was 89 μg/L (42, 141) and 100 (94, 108) μg/g, respectively. UIC increased with higher frequency of dairy intake, ranging from median UIC of 55 (35, 79) μg/L for women consuming dairy products <1 time per week to 124 (98, 151) μg/L in the group consuming dairy >2 times per day (P for trend <0.001). A small group of women reporting complete avoidance of fish (n = 18) had UIC of 50 (21, 123) μg/L and significantly lower I/Cr compared with those who did not report avoidance of fish (58 (34, 134) μg/g vs. 100 (94, 108) μg/g, P = 0.041). Women taking supplements containing iodine (n = 34, 3.5%) had significantly higher UIC compared with those who did not take supplements (141 (77, 263) μg/L vs. 87 (82, 94), P = 0.037).ConclusionFor the first time, insufficient iodine status is being observed in an Icelandic population. There is an urgent need for a public health action aiming at improving iodine status of women of childbearing age in Iceland.

Highlights

Iceland has been an iodine-sufficient nation due to notably high fish and milk consumption
Multiparous women had a higher urinary iodine concentration (UIC) (P = 0.002) and iodine to creatinine (I/Cr) (P = 0.04) than nulliparous women, which could be explained by higher intake of dairy products by multiparous women compared with nulliparous women
Women were asked how many portions of dairy they consumed yesterday, and clear trend toward higher UIC and I/Cr was seen with higher number of portions (Supplementary Table 1)

Summary

Introduction

Iceland has been an iodine-sufficient nation due to notably high fish and milk consumption. Objective: To evaluate the iodine status of pregnant women in Iceland and to determine dietary factors associated with risk for deficiency. Spot urine samples were collected for assessment of urinary iodine concentration (UIC) and creatinine. Diet was assessed using a semiquantitative food frequency questionnaire (FFQ), which provided information on main dietary sources of iodine in the population studied (dairy and fish). Women taking supplements containing iodine (n = 34, 3.5%) had significantly higher UIC compared with those who did not take supplements (141 [77, 263] μg/L vs 87 [82, 94], P = 0.037). Conclusion: For the first time, insufficient iodine status is being observed in an Icelandic population.

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