Suboptimal Iodine Concentration in Breastmilk and Inadequate Iodine Intake among Lactating Women in Norway.

Sigrun Henjum,Elin Lovise Folven Gjengedal,Anne Lise Brantsæter,Anna Dudareva,Inger Aakre,Helle Margrete Meltzer,Anne Marie Lilleengen

doi:10.3390/nu9070643

Abstract

Breastfed infants depend on sufficient maternal iodine intake for optimal growth and neurological development. Despite this, few studies have assessed iodine concentrations in human milk and there is currently no published data on iodine status among lactating women in Norway. The aim of this study was to assess iodine concentrations in breast milk (BMIC) in lactating women and estimate iodine intake. Five Mother and Child Health Centres in Oslo were randomly selected during 2016, and 175 lactating women between 2nd and 28th weeks postpartum participated. Each of the women provided four breastmilk samples which were pooled and analysed for iodine concentrations. Participants also provided information on iodine intake from food and supplements covering the last 24 h and the habitual iodine intake (food frequency questionnaire). The median (p25, p75 percentiles) BMIC was 68 (45, 98) µg/L and 76% had BMIC <100 µg/L. Only 19% had taken an iodine-containing supplement during the last 24 h. The median 24 h iodine intake from food (p25, p75) was 121 (82, 162) µg/day and the total intake (food and supplements) was 134 (95, 222) µg/day. The majority of lactating women had suboptimal BMIC and inadequate intake of iodine from food and supplements.

Highlights

Breastfed infants are entirely dependent on iodine supplied via breastmilk to ensure sufficient thyroid hormone production [1]
Halfofofthe thewomen womenhad had more than four years higher education and were born in reported smoking and had some type of higher education and 65% were born in Norway
There is no scientific consensus on the breast milk iodine concentration (BMIC) that represents a sufficient iodine intake, and a wide range of BMIC values have been reported in areas with varying iodine sufficiency [3,29,40]

Summary

Introduction

Breastfed infants are entirely dependent on iodine supplied via breastmilk to ensure sufficient thyroid hormone production [1]. Infants are vulnerable to iodine deficiency because the fetal and newborn thyroid is immature and has limited iodine stores [2,3,4]. In the Nordic countries, there are indications that pregnant and lactating women are mildly iodine deficient [10,11,12]. This has raised concerns that ID has been overlooked as a public health concern in developed countries, including the Nordic countries [11]

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Conclusion