Long-term iodine nutrition is associated with longevity in older adults: a 20 years’ follow-up of the Randers–Skagen study

Abstract Iodine intake affects the occurrence of thyroid disorders. However, the association of iodine intake with longevity remains to be described. This led us to perform a 20 years’ follow-up on participants from the Randers–Skagen (RaSk) study. Residents in Randers born in 1920 (n 210) and Skagen born in 1918–1923 (n 218) were included in a clinical study in 1997–1998. Mean iodine content in drinking water was 2 µg/l in Randers and 139 µg/l in Skagen. We collected baseline data through questionnaires, performed physical examinations and measured iodine concentrations in spot urine samples. Income data were retrieved from Danish registries. We performed follow-up on mortality until 31 December 2017 using Danish registries. Complete follow-up data were available on 428 out of 430 of participants (99·5 %). At baseline, the median urinary iodine concentration was 55 µg/l in Randers and 160 µg/l in Skagen residents. Participants were long-term residents with 72·8 and 92·7 % residing for more than 25 years in Randers and Skagen, respectively. Cox regression showed that living in Skagen compared with Randers was associated with a lower hazard ratio (HR) of death in both age- and sex-adjusted analyses (HR 0·60, 95 % CI 0·41, 0·87, P = 0·006), but also after adjustment for age, sex, number of drugs, Charlson co-morbidity index, smoking, alcohol and income (HR 0·60, 95 % CI 0·41, 0·87, P = 0·008). Residing in iodine-replete Skagen was associated with increased longevity. This indicates that long-term residency in an iodine-replete environment may be associated with increased longevity compared with residency in an iodine-deficient environment.

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Association between Iodine Nutrition Status and Thyroid Disease-Related Hormone in Korean Adults: Korean National Health and Nutrition Examination Survey VI (2013–2015)

Nutrients ◽

10.3390/nu11112757 ◽

2019 ◽

Vol 11 (11) ◽

pp. 2757 ◽

Cited By ~ 3

Author(s):

Kim ◽

Kwon ◽

Kim ◽

Hong ◽

Park

Keyword(s):

National Health ◽

Thyroid Disease ◽

Urinary Iodine ◽

Iodine Intake ◽

Thyroid Stimulating Hormone ◽

Nutrition Status ◽

Urinary Iodine Concentration ◽

Nutrition Examination Survey ◽

Iodine Nutrition ◽

Health And Nutrition

This study aimed to observe the relationship between iodine nutrition status (dietary iodine intake and estimated iodine intake based on urinary iodine concentration (UIC)) and thyroid disease-related hormones. This study involved 6090 subjects >19 years old with valid UIC, assessed between 2013 and 2015 by the Korean National Health and Nutrition Examination Survey, using a stratified, multistage, clustered probability-sampling design. The estimated iodine intake in participants was measured using UIC and urine creatinine. To examine the effect of iodine intake on thyroid disease, the iodine intake was divided into Korean Dietary Reference Intakes groups, and logistic regression analysis was performed via the surveylogistic procedure to obtain odds ratios (ORs) and 95% confidence intervals (CIs). The estimated iodine intake showed a significant positive correlation with dietary iodine intake (r = 0.021, p < 0.001), UIC (r = 0.918, p < 0.001), and thyroid-stimulating hormone (TSH) (r = 0.043, p < 0.001), but a significant negative correlation with free thyroxine (FT4) (r = −0.037, p < 0.001). Additionally, as the estimated iodine intake increased, age, TSH, and UIC increased, but FT4 decreased (p for trend < 0.0001). The risk of thyroid disease was higher in the “≥tolerable upper intake level (UL ≥ 2400 µg/day)” group than in the “<estimated average requirement (EAR < 150 µg/day)” group in females (OR: 2.418; 95% CI: 1.010–5.787). Also, as iodine intake increased, the risk of thyroid disease increased (p for trend < 0.038).

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Dried Blood Spot Thyroglobulin as a Biomarker of Iodine Status in Pregnant Women

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2016-2829 ◽

2016 ◽

Vol 102 (1) ◽

pp. 23-32 ◽

Cited By ~ 30

Author(s):

Sara Stinca ◽

Maria Andersson ◽

Sandra Weibel ◽

Isabelle Herter-Aeberli ◽

Ralph Fingerhut ◽

...

Keyword(s):

Pregnant Women ◽

Reference Range ◽

Urinary Iodine ◽

Iodine Intake ◽

Dried Blood Spot ◽

Urinary Iodine Concentration ◽

Iodine Nutrition ◽

Cross Sectional ◽

Iodine Status ◽

Blood Spot

Abstract Context: Thyroglobulin (Tg) could be a sensitive biomarker of iodine nutrition in pregnant women (PW). A dried blood spot (DBS) assay would simplify collection and transport in field studies. Objectives: Our aims were to (1) establish and test a reference range for DBS-Tg in PW; (2) determine whether co-measurement of Tg antibodies (Abs) is necessary to define population iodine status. Design, Setting, and Participants: Standardized cross-sectional studies of 3870 PW from 11 countries. For the DBS-Tg reference range, we included TgAb-negative PW (n = 599) from 3 countries with sufficient iodine intake. Main Outcome Measures: We measured the urinary iodine concentration and DBS thyroid-stimulating hormone, total thyroxin, Tg, and TgAb. Results: In the reference population, the median DBS-Tg was 9.2 μg/L (95% confidence interval, 8.7 to 9.8 μg/L) and was not significantly different among trimesters. The reference range was 0.3 to 43.5 μg/L. Over a range of iodine intake, the Tg concentrations were U-shaped. Within countries, the median DBS-Tg and the presence of elevated DBS-Tg did not differ significantly between all PW and PW who were TgAb-negative. Conclusions: A median DBS-Tg of ∼10 μg/L with <3% of values ≥44 μg/L indicated population iodine sufficiency. Concurrent measurement of TgAb did not appear necessary to assess the population iodine status.

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Assessment of the iodine nutritional status among Chinese school-aged children

Endocrine Connections ◽

10.1530/ec-19-0568 ◽

2020 ◽

Vol 9 (5) ◽

pp. 379-386

Author(s):

Ning Yao ◽

Chunbei Zhou ◽

Jun Xie ◽

Xinshu Li ◽

Qianru Zhou ◽

...

Keyword(s):

Nutritional Status ◽

Urinary Iodine ◽

Thyroid Volume ◽

Iodine Content ◽

Iodine Concentration ◽

Iodine Intake ◽

Iodized Salt ◽

Urinary Iodine Concentration ◽

School Aged Children ◽

Goiter Prevalence

Objective The remarkable success of iodine deficiency disorders (IDD) elimination in China has been achieved through a mandatory universal salt iodization (USI) program. The study aims to estimate the relationship between urinary iodine concentration (UIC) and iodine content in edible salt to assess the current iodine nutritional status of school aged children. Methods A total of 5565 students from 26 of 39 districts/counties in Chongqing participated in the study, UIC and iodine content in table salt were measured. Thyroid volumes of 3311 students were examined by ultrasound and goiter prevalence was calculated. Results The overall median UIC of students was 222 μg/L (IQR: 150-313 μg/L). Median UIC was significantly different among groups with non-iodized salt (iodine content <5 mg/kg), inadequately iodized salt (between 5 and 21 mg/kg), adequately iodized (between 21 and 39 mg/kg) and excessively iodized (>39 mg/kg) salt (P < 0.01). The total goiter rate was 1.9% (60/3111) and 6.0% (186/3111) according to Chinese national and WHO reference values, respectively. Thyroid volume and goiter prevalence were not different within the three iodine nutritional status groups (insufficient, adequate and excessive, P > 0.05). Conclusions The efficient implementation of current USI program is able to reduce the goiter prevalence in Chongqing as a low incidence of goiter in school aged children is observed in this study. The widened UIC range of 100–299 μg/L indicating sufficient iodine intake is considered safe with a slim chance of causing goiter or thyroid dysfunction. Further researches were needed to evaluate the applicability of WHO reference in goiter diagnose in Chongqing or identifying more accurate criteria of normal thyroid volume of local students in the future.

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Inadequate iodine intake is associated with subfecundity in mild-to-moderately iodine deficient Norwegian women

Proceedings of The Nutrition Society ◽

10.1017/s0029665120000609 ◽

2020 ◽

Vol 79 (OCE2) ◽

Author(s):

Anne Lise Brantsaeter ◽

Marianne H. Abel ◽

Ida H. Caspersen ◽

Verena Sengpiel ◽

Bo Jacobsson ◽

...

Keyword(s):

Iodine Deficiency ◽

Cox Regression ◽

Smoking Status ◽

Daily Intake ◽

Urinary Iodine ◽

Iodine Intake ◽

Urinary Iodine Concentration ◽

Childbearing Age ◽

Time To Pregnancy ◽

Supplement Use

AbstractIodine is an essential micronutrient and an integral part of the thyroid hormones. In women of childbearing age, the estimated average iodine requirement is 95 μg/day and the recommended daily intake is 150 μg/day. While severe iodine deficiency poses reproductive risks, including infertility and abortions, the potential impact of mild-to-moderate iodine deficiency on subfecundity is unknown.We examined whether iodine intake was associated with risk of subfecundity (i.e. > 12 months trying to get pregnant) in a large cohort of mild-to-moderately iodine deficient women.Women enrolled in the Norwegian Mother and Child Cohort Study in gestational week 15 were asked to report whether the pregnancy was planned and how many months the couple had sexual relations without any contraception before getting pregnant. Information about time to pregnancy, maternal characteristics and iodine intake was available for 56,416 planned pregnancies. The median (interquartile range) time to pregnancy was 1.5 (0.5–6.0) months and the prevalence of subfecundity was 10.8%). We used iodine intake assessed by a validated food frequency questionnaire administered in pregnancy as a proxy for long-term (pre-pregnancy) iodine intake. We used logistic regression to estimate the association between iodine intake and subfecundity, using flexible modelling with restricted cubic splines, and adjusted for maternal age, BMI, parity, education, smoking status, energy intake and fiber intake. The median calculated iodine intake was 121 μg/day and the median urinary iodine concentration in a subsample of n = 2795 women was 69 μg/L.The prevalence of subfecundity was lowest for iodine intakes ~100 μg/day and increased at lower intakes (p overall = 0.005). Compared to an intake of 100 μg/day (reference), intakes ~75 μg/day was associated with 5% (95%CI: 1%, 9%) higher prevalence and intakes ~50 μg/day with 14% (95%CI: 4%, 26%) higher prevalence. Use of dietary supplements was recorded only for the last 6 months prior to conception and women were included in the analysis regardless of their reported supplement use. In a sensitivity analysis, we excluding women who reported iodine-containing supplement use in the period 26–9 weeks before conception and the result remained unchanged. We also modelled time to pregnancy by Cox regression, and the result was consistent with the result for subfecundity.The only good dietary sources of iodine in Norway are milk and white fish, and many women of fertile age have low intakes of these food items. This study shows that low habitual iodine intake may be a risk factor for subfecundity.

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Abstract P359: Assessment of Household Salt Types, Iodine Intake, and Iodine Status in 2019-2020 NHANES

Circulation ◽

10.1161/circ.141.suppl_1.p359 ◽

2020 ◽

Vol 141 (Suppl_1) ◽

Author(s):

Abby G Ershow ◽

Jaime Gahche ◽

Nancy Potischman ◽

Judith Spungen ◽

Pamela Pehrsson

Keyword(s):

At Risk ◽

Dietary Supplements ◽

Age Groups ◽

Urinary Iodine ◽

Iodine Content ◽

Iodine Intake ◽

Iodized Salt ◽

Urinary Iodine Concentration ◽

Iodine Status ◽

The U.S

Background: Iodine is an essential nutrient required for normal thyroid function in all age groups as well as healthy fetal, infant, and child development and growth. Because iodine levels in most foods are low, iodine usually must be provided through dietary supplements or fortified foods (such as salt). In recent NHANES cycles, sub-optimal iodine status has been observed in some U.S. populations, most notably pregnant women. Recent health campaigns have emphasized consuming less sodium and have focused on the primary source of the excess sodium in the U.S. diet: commercially prepared foods, most of which are made with non-iodized salt. Also, recent secular trends towards less home cooking and more use of non-iodized table salts may be contributing to relatively low usage of iodized salt, which was estimated in 2014 to comprise only half of retail salt sales. Therefore, for individuals who also limit their home use of salt in food preparation or at the table, an unintended consequence may be a decline in iodine intake. Population-level data thus are needed on the relative contributions of various foods to iodine intake in relation to iodine status markers, to characterize population groups at risk and develop guidance on appropriate dietary and supplementation strategies. Objective: Describe new measures of iodine intake and iodine status added into NHANES 2019-20, which is a nationally representative survey of the U.S. population. Methods: Iodine intake is being assessed through a questionnaire about household salt types (such as iodized salt or sea salt) and measured iodine content of household iodized salt, as well as individual 24-hour dietary recalls and use of iodine containing dietary supplements. This will be the first time NHANES will estimate dietary iodine intake using a newly developed USDA Special Interest Database on Iodine Content of Foods. Biomarkers include a thyroid panel (including thyroglobulin), inhibitors of iodine uptake in the thyroid (e.g., perchlorates), and urinary iodine concentration. Conclusions: The upcoming NHANES cycle will yield novel data on U.S. population coverage of household iodized salt, as well as individual thyroid and iodine status in relation to dietary iodine intake. Groups at risk from increased physiologic need or dietary preferences that limit iodine sources will be identified. A key tool in undertaking this work will be a new food composition database on the iodine content of U.S. foods. Clarification of key sources of iodine in the U.S. diet will be important in developing dietary guidance.

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Iodine nutrition status in clinically euthyroid pregnant women attending in BSMMU

Bangabandhu Sheikh Mujib Medical University Journal ◽

10.3329/bsmmuj.v9i1.28942 ◽

2016 ◽

Vol 9 (1) ◽

pp. 38

Author(s):

Md. Anowar Hossain ◽

M. Abul Hasanat ◽

Murshed Ahamed Khan ◽

Jobaida Naznin ◽

Kazi Ashraful Alam ◽

...

Keyword(s):

Pregnant Women ◽

Urinary Iodine ◽

Iodine Content ◽

Iodine Concentration ◽

Nutrition Status ◽

Urinary Iodine Concentration ◽

Digestion Method ◽

Iodine Nutrition ◽

Cross Sectional ◽

Nutritional Problem

Background: Iodine deficiency disorders (IDD) are common nutritional problem globally. All groups of people are affected by it, but the pregnant women and their neonates are most vulnerable.Objectives: This study was carried out to see the iodine status of pregnant women using median urinary iodine concentration (MUI) as a measure of outcome. Methods: This cross sectional observational study assessed the MUI in casual urine samples from 225 pregnant women (75 pregnants from each trimester) and 75 non-pregnant healthy controls. The urinary iodine content was estimated in urine sample using the method of Dunn et al. with the modification of Sandell & Kolthoff (wet digestion method).Results: Median value of urinary iodine in pregnant women was 48.21Ug/L compared to 52.27

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Iodine Status and Thyroid Function in a Group of Seaweed Consumers in Norway

Nutrients ◽

10.3390/nu12113483 ◽

2020 ◽

Vol 12 (11) ◽

pp. 3483

Author(s):

Inger Aakre ◽

Lidunn Tveito Evensen ◽

Marian Kjellevold ◽

Lisbeth Dahl ◽

Sigrun Henjum ◽

...

Keyword(s):

Thyroid Function ◽

Urinary Iodine ◽

Iodine Content ◽

Iodine Concentration ◽

Iodine Intake ◽

Thyroid Stimulating Hormone ◽

Urinary Iodine Concentration ◽

Free Triiodothyronine ◽

Iodine Status ◽

Excessive Iodine

Seaweeds, or macroalgae, may be a good dietary iodine source but also a source of excessive iodine intake. The main aim in this study was to describe the iodine status and thyroid function in a group of macroalgae consumers. Two urine samples were collected from each participant (n = 44) to measure urinary iodine concentration (UIC) after habitual consumption of seaweed. Serum thyroid stimulating hormone (TSH), free thyroxine (fT4), free triiodothyronine (fT3), and peroxidase autoantibody (TPOAb), were measured in a subgroup (n = 19). A food frequency questionnaire and an iodine-specific 24 h recall were used to assess iodine intake and macroalgae consumption. The median (p25–p75) UIC was 1200 (370–2850) μg/L. Median (p25–p75) estimated dietary iodine intake, excluding macroalgae, was 110 (78–680) μg/day, indicating that seaweed was the major contributor to the iodine intake. TSH levels were within the reference values, but higher than in other comparable population groups. One third of the participants used seaweeds daily, and sugar kelp, winged kelp, dulse and laver were the most common species. Labelling of iodine content was lacking for a large share of the products consumed. This study found excessive iodine status in macroalgae consumers after intake of dietary seaweeds. Including macroalgae in the diet may give excessive iodine exposure, and consumers should be made aware of the risk associated with inclusion of macroalgae in their diet.

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Naturally occurring iodine in humic substances in drinking water in Denmark is bioavailable and determines population iodine intake

British Journal Of Nutrition ◽

10.1017/s0007114507803941 ◽

2008 ◽

Vol 99 (2) ◽

pp. 319-325 ◽

Cited By ~ 23

Author(s):

Stig Andersen ◽

Klaus M. Pedersen ◽

Finn Iversen ◽

Steen Terpling ◽

Peter Gustenhoff ◽

...

Keyword(s):

Drinking Water ◽

Humic Substances ◽

Natural Waters ◽

Tap Water ◽

Urinary Iodine ◽

Iodine Content ◽

Iodine Intake ◽

Urinary Iodine Excretion ◽

Spot Urine ◽

Naturally Occurring

Iodine intake is important for thyroid function. Iodine content of natural waters is high in some areas and occurs bound in humic substances. Tap water is a major dietary source but bioavailability of organically bound iodine may be impaired. The objective was to assess if naturally occurring iodine bound in humic substances is bioavailable. Tap water was collected at Randers and Skagen waterworks and spot urine samples were collected from 430 long-term Randers and Skagen dwellers, who filled in a questionnaire. Tap water contained 2 μg/l elemental iodine in Randers and 140 μg/l iodine bound in humic substances in Skagen. Median (25; 75 percentile) urinary iodine excretion among Randers and Skagen dwellers not using iodine-containing supplements was 50 (37; 83) μg/24 h and 177 (137; 219) μg/24 h respectively (P < 0·001). The fraction of samples with iodine below 100 μg/24 h was 85·0 % in Randers and 6·5 % in Skagen (P < 0·001). Use of iodine-containing supplements increased urinary iodine by 60 μg/24 h (P < 0·001). This decreased the number of samples with iodine below 100 μg/24 h to 67·3 % and 5·0 % respectively, but increased the number of samples with iodine above 300 μg/24 h to 2·4 % and 16·1 %. Bioavailability of iodine in humic substances in Skagen tap water was about 85 %. Iodine in natural waters may be elemental or found in humic substances. The fraction available suggests an importance of drinking water supply for population iodine intake, although this may not be adequate to estimate population iodine intake.

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Reliability of studies of iodine intake and recommendations for number of samples in groups and in individuals

British Journal Of Nutrition ◽

10.1017/s0007114507842292 ◽

2007 ◽

Vol 99 (4) ◽

pp. 813-818 ◽

Cited By ~ 151

Author(s):

Stig Andersen ◽

Jesper Karmisholt ◽

Klaus M. Pedersen ◽

Peter Laurberg

Keyword(s):

Standard Deviation ◽

Urinary Iodine ◽

Iodine Intake ◽

Urine Samples ◽

Urinary Iodine Excretion ◽

Iodine Nutrition ◽

Cross Sectional ◽

Spot Urine ◽

Iodine Excretion ◽

And Gender

The iodine intake level in a population is determined in cross-sectional studies. Urinary iodine varies considerably and the reliability of studies of iodine nutrition and the number of samples needed is unsettled. We performed a longitudinal study of sixteen healthy men living in an area of mild to moderate iodine deficiency. Iodine and creatinine concentrations were measured in spot urine samples collected monthly for 13 months. From these data we calculated the number of urine samples needed to determine the iodine excretion level for crude urinary iodine and for 24 h iodine excretion estimated from age- and gender-specific creatinine excretions. We found that mean urinary iodine excretion varied from 30 to 87 μg/l (31 to 91 μg/24 h). Sample iodine varied from 10 to 260 μg/l (20 to 161 μg/24 h). Crude urinary iodine varied more than estimated 24 h iodine excretion (population standard deviation 32v. 26; individual standard deviation 29v. 21; Bartlett's test,P < 0·01 for both). The number of spot urine samples needed to estimate the iodine level in a population with 95 % confidence within a precision range of ± 10 % was about 125 (100 when using estimated 24 h iodine excretions), and within a precision range of ± 5 % was about 500 (400). A precision range of ± 20 % in an individual required twelve urine samples or more (seven when using estimated 24 h iodine excretions). In conclusion, estimating population iodine excretion requires 100–500 spot urine samples for each group or subgroup. Less than ten urine samples in an individual may be misleading.

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Assessment of Iodine Nutrition of School Children in Gonda, India, Indicates Improvement and Effectivity of Salt Iodization

Public Health Nutrition ◽

10.1017/s1368980021001956 ◽

2021 ◽

pp. 1-18

Author(s):

Kushagra Gaurav ◽

Subhash Yadav ◽

Sheo Kumar ◽

Anjali Mishra ◽

Madan M Godbole ◽

...

Keyword(s):

School Children ◽

Urinary Iodine ◽

Thyroid Volume ◽

Iodine Content ◽

North India ◽

Urinary Iodine Concentration ◽

Iodine Nutrition ◽

Cross Sectional ◽

Significant Difference ◽

Salt Iodine

Abstract Objective: To study the total goiter rate (TGR), urinary iodine concentration (UIC), and salt iodine content among school children in a previously endemic area for severe iodine deficiency disorder (IDD). Design: Cross-sectional epidemiological study. Setting: The study was carried out in the Gonda district (sub-Himalayan region) of North India. Participants: Nine hundred and seventy-seven school children (6-12 years) were studied for parameters such as height, weight, UIC, and salt iodine content. Thyroid volume (TV) was measured by ultrasonography to estimate TGR. Results: The overall TGR in the study population was 2.8% (95% CI: 1.8-3.8%). No significant difference in TGR was observed between boys and girls (3.5% vs. 1.9%, p=0.2). There was a non-significant trend of increasing TGR with age (p=0.05). Median UIC was 157.1 μg/L (IQR: 94.5-244.9). At the time of the study, 97% of salt sample were iodized and nearly 86% of salt samples had iodine content higher than or equal to 15 ppm. Overall, TGR was significantly lower (2.8% vs. 31.0%, p<0.001), and median UIC was significantly higher (157.1 vs. 100.0 μg/L, p<0.05) than reported in the same area in 2009. Conclusions: A marked improvement was seen in overall iodine nutrition in the Gonda district after three and a half decades of USI. To sustainably control IDD, USI and other programs such as health education, must be continuously implemented along with putting mechanisms to monitor the program at regular intervals in place.

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