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Background: The relationship between iodine intake and depression is unknown. The aim of the present study was to investigate whether iodine intake was associated with symptoms of perinatal emotional distress and depression in a mild- to moderately iodine deficient population., Methods: The study population comprised 67,812 women with 77,927 pregnancies participating in the Norwegian Mother, Father and Child Cohort Study. Self-reported emotional distress and depressive symptoms were reported in pregnancy and at six months postpartum. Iodine intake was assessed by a food frequency questionnaire in mid-pregnancy. Urinary iodine concentration (UIC) was available for 2792 pregnancies., Results: The median iodine intake from food was 121 μg/day and the median UIC was 68 μg/L. The prevalence of high scores for emotional distress was 6.6 % in pregnancy and 5.8 % six months postpartum, and for high scores on postpartum depression it was 10.3 %. In non-users of iodine supplements (63 %), a low maternal iodine intake from food (lower than ~100-150 μg/day) was associated with increased risk of high scores of emotional distress and depression both in pregnancy and six months postpartum (p < 0.001). Iodine supplement use was associated with increased risk of high scores of emotional distress in pregnancy compared to no supplement use or use of supplements without iodine., Limitations: Observational design, self-report information, and short scales to assess symptoms of emotional distress and depression., Conclusion: A low habitual iodine intake was associated with increased prevalence of perinatal emotional distress and depression. The potential non-beneficial effect of iodine supplements may have biological explanations. More studies are needed., Competing Interests: Conflict of Interest M.H.A. was until Dec. 2019 employed by the Norwegian dairy company TINE SA, and she participated in this project as an industrial Ph.D.-student financed partly by TINE SA and partly by The Research Council of Norway. This project is designed, owned, and administered by The Norwegian Institute of Public Health (NIPH) and analysis of the data follow from protocol. All results of analysis in the project are to be published regardless of the results. TINE SA supported the project to raise awareness on the importance of iodine and to gain more knowledge about the potential health effects of milk in the Norwegian diet. Today, M.H.A. is a full-time researcher at the NIPH. The other authors declare that they have no competing interests., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Severe iodine deficiency impacts fertility and reproductive outcomes. The potential effects of mild-to-moderate iodine deficiency are not well known. The aim of this study was to examine whether iodine intake was associated with subfecundity (i.e. > 12 months trying to get pregnant), foetal growth, and adverse pregnancy outcomes in a mild-to-moderately iodine-deficient population., Methods: We used the Norwegian Mother, Father and Child Cohort Study (MoBa) and included 78,318 pregnancies with data on iodine intake and pregnancy outcomes. Iodine intake was calculated using an extensive food frequency questionnaire in mid-pregnancy. In addition, urinary iodine concentration was available in a subsample of 2795 pregnancies. Associations were modelled continuously by multivariable regression controlling for a range of confounding factors., Results: The median iodine intake from food was 121 μg/day and the median urinary iodine was 69 μg/L, confirming mild-to-moderate iodine deficiency. In non-users of iodine supplements (n = 49,187), low iodine intake (< 100-150 μg/day) was associated with increased risk of preeclampsia (aOR = 1.14 (95% CI 1.08, 1.22) at 75 vs. 100 μg/day, p overall < 0.001), preterm delivery before gestational week 37 (aOR = 1.10 (1.04, 1.16) at 75 vs. 100 μg/day, p overall = 0.003), and reduced foetal growth (- 0.08 SD (- 0.10, - 0.06) difference in birth weight z-score at 75 vs. 150 μg/day, p overall < 0.001), but not with early preterm delivery or intrauterine death. In planned pregnancies (n = 56,416), having an iodine intake lower than ~ 100 μg/day was associated with increased prevalence of subfecundity (aOR = 1.05 (1.01, 1.09) at 75 μg/day vs. 100 μg/day, p overall = 0.005). Long-term iodine supplement use (initiated before pregnancy) was associated with increased foetal growth (+ 0.05 SD (0.03, 0.07) on birth weight z-score, p < 0.001) and reduced risk of preeclampsia (aOR 0.85 (0.74, 0.98), p = 0.022), but not with the other adverse pregnancy outcomes. Urinary iodine concentration was not associated with any of the dichotomous outcomes, but positively associated with foetal growth (n = 2795, p overall = 0.017)., Conclusions: This study shows that a low iodine intake was associated with restricted foetal growth and a higher prevalence of preeclampsia in these mild-to-moderately iodine-deficient women. Results also indicated increased risk of subfecundity and preterm delivery. Initiating iodine supplement use in pregnancy may be too late.

Purpose: Some studies indicate that mild-to-moderate iodine deficiency in pregnant women might negatively affect offspring neurocognitive development, including previous results from the Norwegian Mother and Child Cohort study (MoBa) exploring maternally reported child development at age 3 years. The aim of this follow-up study was to investigate whether maternal iodine intake in pregnancy is associated with language and learning at 8 years of age., Methods: The study sample includes 39,471 mother-child pairs participating in MoBa with available information from a validated food frequency questionnaire covering the first half of pregnancy and a questionnaire on child neurocognitive development at 8 years. Multivariable regression was used to explore associations of iodine intake from food and supplements with maternally reported child outcomes., Results: Maternal iodine intake from food less than ~ 150 µg/day was associated with poorer child language skills (p-overall = 0.013), reading skills (p-overall = 0.019), and writing skills (p-overall = 0.004) as well as poorer school test result in reading (p < 0.001), and increased likelihood of the child receiving special educational services (p-overall = 0.042) (in non-iodine supplement users). Although significant, differences were generally small. Maternal use of iodine supplements in pregnancy was not significantly associated with any of the outcomes., Conclusions: Low habitual iodine intake in pregnant women, i.e., lower than the recommended intake for non-pregnant women, was associated with mothers reporting poorer child language, school performance, and increased likelihood of special educational services. We found no indications of benefits or harm of using iodine-containing supplements in pregnancy. Initiating use in pregnancy might be too late.

Background: In 2016, the Norwegian National Nutrition Council concluded that inadequate iodine intake is widespread in sections of the Norwegian population, and that effective measures should be undertaken immediately. This literature review aims to summarise articles published since January 2016 that describe the iodine intake in Norway., Material and Method: Literature searches were conducted in PubMed and Embase. Altogether thirteen articles that reported intake of iodine from the diet or urinary iodine concentration were included., Results: The recent studies confirm that inadequate iodine intake is widespread among women of fertile age, pregnant and breastfeeding women, infants who are exclusively breastfed, elderly persons, vegans and immigrants. There are few sources of iodine in the diet, and persons who avoid or have a low intake of milk and white fish are particularly vulnerable., Interpretation: Inadequate iodine intake is a matter of particular concern in women of fertile age. Healthcare personnel should be aware of this and in certain cases recommend iodine-rich foods or iodine supplements to these and other vulnerable groups.

Background: Studies indicate that mild to moderate iodine deficiency in pregnancy may have a long-term negative impact on child neurodevelopment. These effects are likely mediated via changes in maternal thyroid function, since iodine is essential for the production of thyroid hormones. However, the impact of iodine availability on thyroid function during pregnancy and on thyroid function reference ranges are understudied. The aim of this study was to investigate the association between iodine intake and thyroid function during pregnancy., Design: In a population-based pregnancy cohort including 2910 pregnant women participating in The Norwegian Mother and Child Cohort Study, we explored cross sectional associations of maternal iodine intake measured (1) by a food frequency questionnaire and (2) as iodine concentration in a spot urine sample, with plasma thyroid hormones and antibodies., Results: Biological samples were collected in mean gestational week 18.5 (standard deviation 1.3) and diet was assessed in gestational week 22. Median iodine intake from food was 121 μg/day (interquartile range 90, 160), and 40% reported use of iodine-containing supplements in pregnancy. Median urinary iodine concentration (UIC) was 59 μg/L among those who did not use supplements and 98 μg/L in the women reporting current use at the time of sampling, indicating mild to moderate iodine deficiency in both groups. Iodine intake as measured by the food frequency questionnaire was not associated with the outcome measures, while UIC was inversely associated with FT3 (p = 0.002) and FT4 (p < 0.001). Introduction of an iodine-containing supplement after gestational week 12 was associated with indications of lower thyroid hormone production (lower FT4, p = 0.027, and nonsignificantly lower FT3, p = 0.17). The 2.5th and 97.5th percentiles of TSH, FT4, and FT3 were not significantly different by groups defined by calculated iodine intake or by UIC., Conclusion: The results indicate that mild to moderate iodine deficiency affect thyroid function in pregnancy. However, the differences were small, suggesting that normal reference ranges can be determined based on data also from mildly iodine deficient populations, but this needs to be further studied. Introducing an iodine-containing supplement might temporarily inhibit thyroid hormone production and/or release.

Inadequate iodine status affects the synthesis of the thyroid hormones and may impair brain development in fetal life. The aim of this study was to explore the association between maternal iodine status in pregnancy measured by urinary iodine concentration (UIC) and child neurodevelopment at age 6, 12 and 18 months in a population-based cohort. In total, 1036 families from nine locations in Norway were enrolled in the little in Norway cohort. The present study includes n = 851 mother-child pairs with singleton pregnancies, no use of thyroid medication in pregnancy, no severe genetic disorder, data on exposure (UIC) in pregnancy and developmental outcomes (Bayley Scales of Infant and Toddler Development, third edition). Data collection also included general information from questionnaires. We examined associations between UIC (and use of iodine-containing supplements) and repeated measures of developmental outcomes using multivariable mixed models. The median UIC in pregnancy was 78 µg/L (IQR 46⁻130), classified as insufficient iodine intake according to the WHO. Eighteen percent reported use of iodine-containing multisupplements. A UIC below ~100 was associated with reduced receptive ( p = 0.025) and expressive language skills ( p = 0.002), but not with reduced cognitive or fine- and gross motor skills. Maternal use of iodine-containing supplements was associated with lower gross motor skills (b = -0.18, 95% CI = -0.33, -0.03, p = 0.02), but not with the other outcome measures. In conclusion, an insufficient iodine intake in pregnancy, reflected in a UIC below ~100 µg/L, was associated with lower infant language skills up to 18 months. The use of iodine-containing supplements was not associated with beneficial effects.

Current knowledge about the relationship between mild to moderately inadequate maternal iodine intake and/or supplemental iodine on child neurodevelopment is sparse. Using information from 77,164 mother-child pairs in the Norwegian Mother and Child Cohort Study, this study explored associations between maternal iodine intake and child attention-deficit/hyperactivity disorder (ADHD) diagnosis, registered in the Norwegian Patient Registry and maternally-reported child ADHD symptoms at eight years of age. Pregnant women reported food and supplement intakes by questionnaire in gestational week 22. In total, 1725 children (2.2%) were diagnosed with ADHD. In non-users of supplemental iodine (53,360 mothers), we found no association between iodine intake from food and risk of child ADHD diagnosis ( p = 0.89), while low iodine from food (<200 µg/day) was associated with higher child ADHD symptom scores (adjusted difference in score up to 0.08 standard deviation (SD), p < 0.001, n = 19,086). In the total sample, we found no evidence of beneficial effects of maternal use of iodine-containing supplements ( n = 23,804) on child ADHD diagnosis or symptom score. Initiation of iodine supplement use in gestational weeks 0-12 was associated with an increased risk of child ADHD (both measures). In conclusion, insufficient maternal iodine intake was associated with increased child ADHD symptom scores at eight years of age, but not with ADHD diagnosis. No reduction of risk was associated with maternal iodine supplement use., Competing Interests: The first author of this paper is employed by a Norwegian dairy company (TINE SA), and she participates in this project as an industrial PhD-student financed partly by the dairy company and partly by The Research Council of Norway. This project is designed, owned and administered by The Norwegian Institute of Public Health and analysis of the data follow from protocol. All results of analysis in the project are to be published regardless of the results. The dairy company supports the study to raise awareness on the importance of iodine and to gain more knowledge about the potential health effects of milk in the Norwegian diet. Apart from the PhD-student, no one from the dairy company has been involved in the study, and in itself, the company had no direct influence on the analysis and interpretation of the results. The other authors had no conflicts of interest.

Background: Severe iodine deficiency in pregnancy has major effects on child neurodevelopment, but less is known about the potential consequences of mild-to-moderate deficiency and iodine supplement use. Objective: We explored the associations between maternal iodine intake and child neurodevelopment at 3 y of age and the potential impact of maternal intake of iodine from supplements on the same outcomes. Methods: This population-based prospective observational study included 48,297 mother-child pairs recruited during pregnancy from 2002 to 2008. Maternal iodine intake was calculated based on a validated food-frequency questionnaire answered during midpregnancy that covered mean intake since the beginning of pregnancy. Associations between iodine intake and maternal-reported child language and motor development and behavior problems were explored by multivariable regression analyses. Results: In 33,047 mother-child pairs, excluding iodine supplement users, maternal iodine intake was associated with child language delay ( P = 0.024), externalizing and internalizing behavior problems (both P < 0.001), and fine motor skills ( P = 0.002) but not gross motor skills or the risk of not walking unaided at 17 mo of age. In 74% of the participants who had an iodine intake <160 μg/d (Estimated Average Requirement), suboptimal iodine intake was estimated to account for ∼5% (95% CI: -5%, 14%) of the cases of language delay, 16% (95% CI: 0%, 21%) of the cases of externalizing behavior problems >1.5 SD, and 16% (95% CI: 10%, 21%) of the cases of internalizing behavior problems >1.5 SD. In 48,297 mother-child pairs, including iodine supplement users, we found no protective effects of supplemental iodine during pregnancy on neurodevelopment. Conclusions: Maternal iodine intake below the Estimated Average Requirement during pregnancy was associated with symptoms of child language delay, behavior problems, and reduced fine motor skills at 3 y of age. The results showed no evidence of a protective effect of iodine supplementation during pregnancy., Competing Interests: Author disclosures: IHC, HMM, MH, REB, HA, JA, LET, and A-LB, no conflicts of interest. MHA is employed by TINE SA. This is a free access article, distributed under terms (http://www.nutrition.org/publications/guidelines-and-policies/license/) that permit unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited., (© 2017 American Society for Nutrition.)

Pregnant women and infants are exceptionally vulnerable to iodine deficiency. The aims of the present study were to estimate iodine intake, to investigate sources of iodine, to identify predictors of low or suboptimal iodine intake (defined as intakes below 100 μg/day and 150 μg/day) in a large population of pregnant Norwegian women and to evaluate iodine status in a sub-population. Iodine intake was calculated based on a validated Food Frequency Questionnaire in the Norwegian Mother and Child Cohort. The median iodine intake was 141 μg/day from food and 166 μg/day from food and supplements. Use of iodine-containing supplements was reported by 31.6%. The main source of iodine from food was dairy products, contributing 67% and 43% in non-supplement and iodine-supplement users, respectively. Of 61,904 women, 16.1% had iodine intake below 100 μg/day, 42.0% had iodine intake below 150 μg/day and only 21.7% reached the WHO/UNICEF/ICCIDD recommendation of 250 μg/day. Dietary behaviors associated with increased risk of low and suboptimal iodine intake were: no use of iodine-containing supplements and low intake of milk/yogurt, seafood and eggs. The median urinary iodine concentration measured in 119 participants (69 μg/L) confirmed insufficient iodine intake. Public health strategies are needed to improve and secure the iodine status of pregnant women in Norway.