Iodine status and determinants in adults in Norway – results from a population-based health examination survey (The HUNT Study)

Marianne Hope Abel; Torunn Holm Totland; Kristin Holvik; Anne Lise Brantsæter; Steinar Krokstad; Bjørn Olav Åsvold; Haakon Eduard Meyer

doi:10.29219/fnr.v68.9761

Marianne Hope Abel Department of Physical Health and Ageing, Norwegian Institute of Public Health, Oslo, Norway https://orcid.org/0000-0001-6519-2064
Torunn Holm Totland Department of Physical Health and Ageing, Norwegian Institute of Public Health, Oslo, Norway https://orcid.org/0000-0001-6663-6907
Kristin Holvik Department of Physical Health and Ageing, Norwegian Institute of Public Health, Oslo, Norway https://orcid.org/0000-0003-3132-2822
Anne Lise Brantsæter Department of Food Safety, Norwegian Institute of Public Health, Oslo, Norway https://orcid.org/0000-0001-6315-7134
Steinar Krokstad Norwegian University of Science and Technology and Levanger Hospital https://orcid.org/0000-0002-2932-6675
Bjørn Olav Åsvold Norwegian University of Science and Technology, NTNU, Levanger, Norway; K.G. Jebsen Center for Genetic Epidemiology, Department of Public Health and Nursing, NTNU, Norwegian University of Science and Technology, Trondheim, Norway; Department of Endocrinology, Clinic of Medicine, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway; 7Department of Community Medicine and Global Health, Institute of Health and Society, University of Oslo, Oslo, Norway https://orcid.org/0000-0003-3837-2101
Haakon Eduard Meyer Department of Physical Health and Ageing, Norwegian Institute of Public Health, Oslo, Norway; Department of Community Medicine and Global Health, Institute of Health and Society, University of Oslo, Oslo, Norway https://orcid.org/0000-0002-3262-8260

DOI: https://doi.org/10.29219/fnr.v68.9761

Keywords: iodine, monitoring, urinary iodine concentration, dietary determinants, cross-sectional study

Abstract

Background: In Norway, there is a lack of knowledge about the iodine status in the general and older adult population, and there is no established national monitoring programme for iodine. Several studies have indicated that iodine deficiency is prevalent in subgroups of the population. Salt iodisation is currently being considered as a measure to increase the population iodine status. In this cross-sectional study, the aim was to evaluate iodine status and determinants in the adult and older adult population in Mid-Norway, before salt iodisation is likely to be initiated.

Methods: The study sample was a subsample of participants in the fourth wave of the population-based Trøndelag Health Study (HUNT4, 2017–2019) with available spot-urine samples. This subsample included participants with 25–64 years (n = 500) and 70–79 years (n = 250). The urine samples were analysed for iodine and creatinine. Information on the habitual intake of milk/yoghurt, fish, supplement use, use of thyroid medication and relevant background factors was collected through a general questionnaire. Multivariable quantile regression was used to model differences in the median urinary iodine concentration (UIC) by determinants. Estimates were weighted to match the age and sex distribution of the Norwegian population aged 25–79 years in 2019.

Results: Median UIC was 97 µg/L (95% confidence interval [CI]: 92, 103) indicating borderline iodine deficiency at a group level. The median UIC increased with age, and iodine status was insufficient in participants below age 55 years (median 92 µg/L [95% CI: 85, 99]). Important determinants of UIC were habitual milk/yoghurt intake, daily supplement use and current use of thyroid medication, but not intake of lean or fatty fish. Risk of mild-to-moderate iodine deficiency was seen in those with a low intake of milk/yoghurt, no supplement use and who did not use thyroid medication. No group was identified as being at risk of iodine excess.

Conclusion: Iodine status was adequate in older adults but mildly deficient in adults under 55 years. Milk intake, supplement use and use of thyroid medication are important determinants of iodine intake in Norway.

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Author Biographies

Marianne Hope Abel, Department of Physical Health and Ageing, Norwegian Institute of Public Health, Oslo, Norway

Researcher, Department of physical health and ageing

Torunn Holm Totland, Department of Physical Health and Ageing, Norwegian Institute of Public Health, Oslo, Norway

Researcher, Department of physical health and ageing

Kristin Holvik, Department of Physical Health and Ageing, Norwegian Institute of Public Health, Oslo, Norway

Researcher, Department of physical health and ageing

Anne Lise Brantsæter, Department of Food Safety, Norwegian Institute of Public Health, Oslo, Norway

Senior researcher, Department of food safety

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