Iodine in Early Life : A cross-sectional study of children 0–2 years of age and their mothers in Norway
Doctoral thesis

Åpne
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https://hdl.handle.net/11250/3131767Utgivelsesdato
2024-06-10Metadata
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Bakgrunn: Jod trengs for produksjonen av tyreoideahormoner, som er viktige for metabolismen og for normal vekst og utvikling av hjernen og nervesystemet. Både for mye og for lite jod kan medføre endringer i produksjonen av disse hormonene og føre til uheldige helseeffekter. Selv om andelen med jodmangel og relaterte sykdommer har blitt betydelig redusert de siste tiårene, er mild-til-moderat jodmangel utbredt i enkelte befolkningsgrupper, både i Norge og i andre land. Til tross for viktigheten av jod for vekst og utvikling, er det kunnskapshull om jodstatus og jodinntak blant små barn.
Mål: Det overordnede målet var å beskrive jodtatus og jodinntak blant barn mellom 0–2 år og deres mødre i Innlandet, samt å estimere sammenhengen mellom mors og barns jodinntak.
Methode: En tverrsnittsstudie ble gjennomført i to faser i Innlandet: fase I) blant mor-barn par (barns alder 0–12 måneder) i to kommuner fra oktober til desember 2018, og fase II) blant mor-barn par (barn 0–2 år) i 30 kommuner fra november 2020 til oktober 2021. Prøver av urin og morsmelk ble samlet inn og analysert for jod. Jodinntak ble beregnet ved bruk av ulike metoder: fase I) spørreskjema for nylig og habituelt inntak, og fase II) repeterte 24-timers kostintervju og matvarefrekvensspørreskjema. I fase II ble det statistiske verktøyet «Multiple Source Method» brukt til å estimere distribusjonen av habituelt inntak av jod fra 24-timers kostintervju.
Resultater: Totalt ble 463 mor-barn par inkludert i analysene av jodinntak og jodstatus (130 fra fase I og 333 fra fase II). I fase I var barnas median jodkonsentrasjon i urin (UIC) 145 μg/L, som indikerer tilstrekkelig jodstatus ifølge grenseverdien satt av WHO på 100 μg/L. Habituelt jodinntak ble ikke estimert for alle barna i fase I, men median nylig (24-timers) jodinntak var 50 μg/dag og innenfor anbefalt inntak [«recommended intake» (RI)] på 50–70 μg/dag (NNR2012).
I fase II, som inkluderte et representativt utvalg mor-barn par fra Innlandet, var barnas median UIC 145 μg/L, også over WHOs grenseverdi for tilstrekkelig jodstatus. Median habituelt jodinntak basert på repeterte 24-timers kostintervju var 83 μg/dag og under nylig oppdatert referanseinntak [«adequate intake», (AI)] for denne aldersgruppen på 90–100 μg/dag (NNR2023). Videre hadde 35% av barna et suboptimalt jodinntak [under «estimated average requirement» (EAR) på 72 μg/dag], og <1 % hadde et for høyt jodinntak [over «upper limit» (UL) på 200 μg/day].
Median UIC blant mødrene i fase II var 92 μg/L, som indikerer utilstrekkelig jodstatus (<100 μg/L). Median jodkonsentrasjon i morsmelk (BMIC) var 74 μg/L. Videre hadde 23% av kvinnene et suboptimalt habituelt jodinntak [under «average requirement» (AR) på 100 μg/dag], mens ingen hadde et for høyt jodinntak (over UL på 600 μg/dag). Barnas UIC og jodinntak var positivt assosiert med BMIC, mors UIC, og mors habituelle jodinntak.
Konklusjon: Barna hadde en adekvat jodstatus på gruppenivå, indikert ved en median UIC over gjeldende grenseverdi på 100 μg/L. 24-timers kostintervjuene indikerte at mer enn en tredjedel av barna hadde et utilstrekkelig jodinntak, mens veldig få barn hadde et for høyt jodinntak. Funnene samsvarer med tidligere funn av lave jodinntak blant ammende kvinner. Med tanke på viktigheten av jod for vekst og utvikling er det behov for tiltak for å øke jodinntaket blant små barn og kvinner i fertil alder. Background: As a component of the thyroid hormones (THs), iodine is a micronutrient essential for normal neurodevelopment and metabolism. Both iodine deficiency and iodine excess may alter TH production and are associated with an increased risk of adverse health effects. While there has been substantial global progress in tackling iodine deficiency disorders over recent decades, mild-to-moderate iodine deficiency remains a threat in certain countries and population groups, including Norway. Despite the importance of iodine in early life, data on iodine nutrition in young children are scarce.
Objectives: The main objective of this thesis was to describe iodine nutrition (iodine status and intake) in children between 0–2 years of age and their mothers in Innlandet County, Norway, and relate it to markers of maternal iodine nutrition.
Methods: A two-phase cross-sectional study in Innlandet County was performed: phase I in mother-infant pairs (infants 0–12 months of age) in two municipalities from October to December 2018, and phase II in mother-child pairs (children 0–2 years of age) in 30 municipalities from November 2020 to October 2021. Urine and breast milk samples were collected and analyzed for iodine. Iodine intake was estimated using different dietary assessment methods: phase I) questionnaires addressing the recent and usual intake of iodine- rich foods, and phase II) repeated 24-hour dietary recalls (24-HRs) and a food frequency questionnaire (FFQ). The second phase applied the Multiple Source Method to estimate usual iodine intake distributions from the repeated 24-HRs.
Results: In total, 463 mother-child pairs were included in the final analyses of iodine nutrition (130 from phase I and 333 from phase II). In phase I, the infant median urinary iodine concentration (UIC) was 146 μg/L, indicating sufficient iodine status according to the current WHO cut-off of 100 μg/L. Usual iodine intake was not estimated for the whole group of children, but the median recent (24-hour) iodine intake was 50 μg/day and within the recommended intake (RI) at that time point of 50–70 μg/day (NNR2012).
In phase II, which evaluated a representative sample of mother-child pairs in Innlandet County, the median UIC in the children was 145 μg/L, which was also above the current WHO cut-off for iodine sufficiency. The median usual iodine intake based on the repeated 24-HRs was 83 μg/day, which was below the updated adequate intake (AI) for this age group of 90–100 μg/day (NNR2023). Further, 35% of the children had a suboptimal usual iodine intake [below the proposed estimated average requirement (EAR) of 72 μg/day], and <1% had an excessive usual iodine intake [above the upper limit (UL) of 200 μg/day].
The median maternal UIC in phase II was 92 μg/L, indicating insufficient iodine status in the women (<100 μg/L), and the median breast milk iodine concentration (BMIC) was 74 μg/L. Further, 23% of the women had a suboptimal usual iodine intake (below the AR of 100 μg/day), while none had an excessive usual iodine intake (above the UL of 600 μg/day). The children’s UIC and iodine intake was positively associated with all markers of maternal iodine nutrition (BMIC, UIC, and estimated iodine intake).
Conclusion: The children had an adequate iodine status on a population level, as indicated by a median UIC above the current cut-off of 100 μg/L. However, the extensive dietary data in phase II suggested that more than a third of the children had a suboptimal usual iodine intake. Furthermore, the proportion of children with an excessive usual iodine intake was low. Our findings support previous findings of a low iodine intake in postpartum and lactating women. Considering the role of iodine for growth and development, urgent measures are required to improve iodine intake in young children and women of childbearing age.
Består av
Paper I. Bakken KS, Aarsland TE, Groufh-Jacobsen S, Solvik BS, Gjengedal ELF, Henjum S, Strand TA. Adequate Urinary Iodine Concentration among Infants in the Inland Area of Norway. Nutrients. 2021;13(6). The article is available at: https://hdl.handle.net/11250/2770727.Paper II. Aarsland TE, Kaldenbach S, Bakken KS, Solvik BS, Holten-Andersen M, Strand TA. Inadequate Iodine Intake in Mothers of Young Children in Innlandet County, Norway. Curr Dev Nutr, 2023. 7(3): p. 100047. The article is available at: https://hdl.handle.net/11250/3115074.
Paper III. Aarsland TE, Solvik BS, Bakken KS, Sleire SN, Kaldenbach S, Holten-Andersen M, Nermo KR, Fauskerud IT, Østvedt TH, Lohne S, Gjengedaal ELF, Strand TA. Iodine Nutrition in Children ≤2 years of Age in Norway. J Nutr, 2023. 153(11): p. 3237-3246. The article is available at: https://hdl.handle.net/11250/3112675.