A multi-centre pilot study of iodine status in UK schoolchildren, aged 8-10 years

Climate changes affecting global iodine status

Global warming is now universally acknowledged as being responsible for dramatic climate changes with rising sea levels, unprecedented temperatures, resulting fires and threatened widespread species loss. While these effects are extremely damaging, threatening the future of life on our planet, one unexpected and paradoxically beneficial consequence could be a significant contribution to global iodine supply. Climate change and associated global warming are not the primary causes of increased iodine supply, which results from the reaction of ozone (O3) arising from both natural and anthropogenic pollution sources with iodide (I-) present in the oceans and in seaweeds (macro- and microalgae) in coastal waters, producing gaseous iodine (I2). The reaction serves as negative feedback, serving a dual purpose, both diminishing ozone pollution in the lower atmosphere and thereby increasing I2. The potential of this I2 to significantly contribute to human iodine intake is examined in the context of I2 released in a seaweed-abundant coastal area. The bioavailability of the generated I2 offers a long-term possibility of increasing global iodine status and thereby promoting thyroidal health. It is hoped that highlighting possible changes in iodine bioavailability might encourage the health community to address this issue.

The impact of replacing milk with plant-based alternatives on iodine intake: a dietary modelling study

PURPOSE

Cow's milk is the primary source of iodine in the UK, but consumption of plant-based milk alternatives (PBMA) is increasing and these products are often not fortified with iodine. We evaluated the impact that replacing current milk consumption with PBMA would have on iodine intake.

METHODS

We used data from the National Diet and Nutrition Survey (2016-2019) for children (1.5-10 years), girls 11-18 years, and women of reproductive age (WRA). We used a dietary modelling approach with scenarios using brand-level iodine-fortification data (0, 13, 22.5, 27.4 and 45 µg/100 mL). Relative to usual diet, we calculated change in iodine intake, and the proportion with intake below the Lower Reference Nutrient Intake (LRNI) or above the upper limit.

RESULTS

For all groups, replacement with PBMA, either unfortified or fortified at the lowest concentration, resulted in a meaningful decrease in iodine intake, and increased the proportion with intake < LRNI; compared to usual diet, iodine intake reduced by 58% in children 1.5-3 years (127 vs. 53 µg/day) and the proportion with intake < LRNI increased in girls (11-18 years; 20% to 48%) and WRA (13% to 33%) if an unfortified PBMA was used. Replacement of milk with PBMA fortified at 27.4 µg/100 mL had the lowest impact.

CONCLUSION

Replacing milk with commercially available PBMAs has potential to reduce population iodine intake, depending on the fortification level. PBMAs fortified with ≥ 22.5 and < 45 µg iodine/100 mL would be required to minimize the impact on iodine intake. Research is needed on the impact of total dairy replacement.

Association between Elevated Iodine Intake and IQ among School Children in Portugal

The goal of this work was to examine whether elevated iodine intake was associated with adverse effects on IQ among school-age children in Portugal. In a representative sample of children from the north of the country, IQ percentiles by age (assessed with Raven’s Colored Progressive Matrices) were dichotomized to <50 (“below-average” IQs) and ≥50. Morning urine iodine concentrations, corrected for creatinine, were dichotomized to <250 µg/g and ≥250 µg/g, according to the European Commission/Scientific Committee on Food’s tolerable upper level of daily iodine intake for young children. Data were examined with Chi-square tests, logistic regression, and GLM univariate analysis. The sample (N = 1965) was classified as generally iodine-adequate (median urinary iodine concentration = 129 µg/L; median iodine-to-creatinine ratio = 126 µg/g) according to the WHO’s criteria. A greater proportion of children in the ≥250 µg/g group had below-average IQs, compared to children with less than 250 µg/g (p = 0.037), despite a sizable (though non-significant) proportion of children in the less-than-250 µg/g group also presenting below-average IQs, at the bottom of the iodine distribution (<50 µg/g). The proportion of below-average IQs increased with increasingly elevated iodine concentrations (p = 0.047). The association remained significant after the adjustment for confounders, with the elevated iodine group showing increased odds of having below-average IQs when compared with the non-elevated iodine group (OR 1.55; 95% CI 1.11−2.17; p = 0.011). Consistently, the former group presented a lower mean IQ than the latter (p = 0.006). High iodine intake was associated with lower IQs even in a population classified as iodine-adequate. These results bear on child cognition and on initiatives involving iodine supplementation.

Thyroglobulin levels among iodine deficient pregnant women living in Northern Ireland

BACKGROUND

Iodine deficiency has re-emerged among pregnant cohorts in the UK. Thyroglobulin (Tg) is a protein produced uniquely by the thyroid gland which appears to mount a U-shaped response to extremes of iodine status. Tg has been suggested as an alternative marker for chronic iodine deficiency but the value of Tg in pregnancy has not been fully elucidated. A recent non-European study suggested a median Tg ≤10 µg/L with <3% of values >44 µg/L was indicative of sufficiency in the second trimester of pregnancy.

METHODS

We measured serum Tg levels in each trimester in 241 pregnant women living in Northern Ireland, a population with mild iodine deficiency at all stages of pregnancy as defined by urinary iodine concentration (UIC) and iodine: creatinine ratio (ICR). Women with Tg antibodies (6% in 1st trimester) were excluded.

RESULTS

The median UIC in this cohort was in the deficient range at 73, 94 and 117 µg/L in sequential trimesters (adequacy ≥ 150 µg/L). Corresponding median Tg levels were 19, 16 and 16 µg/L respectively. Median Tg for all samples was 17 μg/L (IQR 11-31) suggestive of iodine deficiency. Tg was >44 μg/L in 14.3%, 9.4% and 12.4% of women in sequential trimesters respectively. Women with either UIC/ICR below the cut-offs 150 µg/L and 150 µg/g creatinine had higher Tg concentrations in 1st and 2nd trimester (p < 0.01; p < 0.001) but not in 3rd trimester.

CONCLUSION

This study adds to the evolving evidence that Tg measurement is of value in reflecting iodine status in pregnancy.

Dairy as a Source of Iodine and Protein in the UK: Implications for Human Health Across the Life Course, and Future Policy and Research

This narrative review summarizes key concepts in dairy nutrition for supporting human health throughout the life course. Milk and dairy products have been a staple component of our diet for thousands of years and provide a wide range of important nutrients that are otherwise difficult to obtain from dairy-free diets. In this review, we provide a broad perspective on the nutritional roles of iodine and dairy protein in supporting human health during pregnancy and early life, childhood and adolescence, mid- and later-life. New methodologies to identify biomarkers of dairy intake via high-throughput mass spectrometry are discussed, and new concepts such as the role of the food matrix in dairy nutrition are introduced. Finally, future policy and research related to the consumption of dairy and non-dairy alternatives for health are discussed with a view to improving nutritional status across the lifespan.

The Characteristics of Iodine Nutrition Status in China After 20 Years of Universal Salt Iodization: An Epidemiology Study Covering 31 Provinces

Background: Despite the implementation of the universal salt iodization (USI) program for correction of iodine deficiency in China for ∼20 years, the actual iodine nutrition status of Chinese residents and the prevalence of iodine deficiency and iodine excess are issues that need to be addressed. This nationally representative cross-sectional study was conducted across all 31 provinces of mainland China to gather extensive data on iodine nutrition status and the influential factors. Methods: This study included 78,470 participants, aged 18 years or older, who were interviewed and asked to answer a questionnaire. Urine iodine concentration (UIC) was measured by the inductively coupled plasma mass spectrometry method, and goiter was examined by thyroid ultrasonography. In addition, sixty 9-11 years old school children in each province were randomly selected to evaluate the UIC and thyroid ultrasonography. The iodine nutrition status was determined according to the World Health Organization guidelines. Results: The iodized salt coverage was 95.37%. The median urine iodine (MUI) was 177.89 μg/L (interquartile range [IQR], 117.89-263.90 μg/L) and goiter prevalence was 1.17% (confidence interval [95% CI 0.95-1.43]) in the adult population. The MUI was 199.75 μg/L (IQR, 128.41-303.37 μg/L) in school-age children, and goiter prevalence was 3.50% [95% CI, 2.93-4.13]. The percentage of individuals with UIC <50 μg/L was 3.43%, <20%. Analysis indicated that sex, age, geographic factors, body mass index, and smoking habits influence the iodine nutrition level. Conclusion: The mandatory USI program has successfully eliminated iodine deficiency disorders, and the findings indicate that the iodine nutrition level in the general population is within the safe range.

Food sources of iodine in schoolchildren and relationship with 24-h urinary iodine excretion in Victoria, Australia

Dietary recalls have been used previously to identify food sources of iodine in Australian schoolchildren. Dietary assessment can provide information on the relative contributions of individual food groups which can be related to a robust objective measure of daily intake (24-h urinary iodine excretion (UIE)). In Australia, the government has mandated the use of iodised salt in breadmaking to address iodine deficiency. The aim of this study was to determine the dietary intake and food sources of iodine to assess their contribution to iodine excretion (UIE) in a sample of Australian schoolchildren. In 2011-2013, UIE was assessed using a single 24-h urine sample and dietary intake was assessed using one 24-h dietary recall in a convenience sample of primary schoolchildren from schools in Victoria, Australia. Of the 454 children with a valid recall and urine sample, 55 % were male (average age 10·1 (1·3 (sd) years). Mean UIE and dietary iodine intake were 108 (sd 54) and 172 (sd 74) μg/d, respectively. Dietary assessment indicated that bread and milk were the main food sources of iodine, contributing 27 and 25 %, respectively, to dietary iodine. Milk but not bread intake was positively associated with UIE. Multiple regression (adjusted for school cluster, age and sex) indicated that for every 100 g increase in milk consumption, there was a 3 μg/d increase in UIE (β = 4·0 (se 0·9), P < 0·001). In conclusion, both bread and milk were important contributors to dietary iodine intake; however, consumption of bread was not associated with daily iodine excretion in this group of Australian schoolchildren.

Iodine, Seaweed, and the Thyroid

BACKGOUND

Even a minor iodine deficiency can result in adverse thyroidal health consequences while excess iodine intake can also result in thyroid function disorders. One source of iodine is seaweed which as a foodstuff is enjoying an increasing profile in Western countries. Apart from its potential involvement in thyroidal health, gaseous iodine released from seaweeds plays a significant role in influencing coastal climate through cloud formation.

SUMMARY

Sources of dietary iodine, its assessment, recommended dietary intake, and consequences of iodine excess are outlined. The benefits and possible dangers of dietary intake of iodine-rich seaweed are described. Studies linking seaweed intake to breast cancer prevalence are discussed as is the role of gaseous iodine released from seaweeds influencing weather patterns and contributing to iodine intake in coastal populations.

KEY MESSAGES

Universal salt iodization remains the optimum method of achieving optimum iodine status. Promoting increased dietary iodine intake is recommended in young women, in early pregnancy, and in vegan and vegetarian diets. Even where iodine intake is enhanced, regular assessment of iodine status is necessary. Caution against consumption of brown seaweeds (kelps) is required as even small amounts can have antithyroid actions while product labelling may be insufficient. Gaseous iodine produced from seaweeds can have a significant effect on cloud formation and associated global warming/cooling. Increased overall iodine deposition through rainfall and apparent uptake in populations dwelling in seaweed-rich coastal regions may provide a partial natural remedy to global iodine deficits.

Current iodine nutrition status in Poland (2017): is the Polish model of obligatory iodine prophylaxis able to eliminate iodine deficiency in the population?

OBJECTIVE

The monitoring of the populations' iodine status is an essential part of successful programmes of iodine deficiency elimination. The current study aimed at the evaluation of current iodine nutrition in school children, pregnant and lactating women as a marker of the effectiveness and sustainability of mandatory iodine prophylaxis in Poland.

DESIGN

The following iodine nutrition indicators were used: urinary iodine concentration (UIC) (all participants) and serum thyroglobulin (pregnant and lactating women).

SETTING

The study was conducted in 2017 within the National Health Programme in five regions of Poland.

PARTICIPANTS

The research included 300 pregnant women, 100 lactating women and 1000 school children (aged 6-12 years).

RESULTS

In pregnant women, median UIC was 111·6 µg/l; there was no significant difference in median UIC according to the region of residence. In 8 % of pregnant women, thyroglobulin level was >40 ng/ml (median thyroglobulin 13·3 ng/ml). In lactating women, median UIC was 68·0 µg/l. A significant inter-regional difference was noted (P = 0·0143). In 18 % of breastfeeding women, thyroglobulin level was >40 ng/ml (median thyroglobulin 18·5 ng/ml). According to the WHO criteria, the investigated sample of pregnant and lactating women was iodine-deficient. Median UIC in school children was 119·8 µg/l (with significant inter-regional variation; P = 0·0000), which is consistent with iodine sufficiency. Ninety-four children (9·4 %) had UIC < 50 µg/l.

CONCLUSIONS

Mandatory iodisation of household salt in Poland has led to a sustainable optimisation of iodine status in the general population. However, it has failed to assure adequate iodine nutrition during pregnancy and lactation.

Histopathological Verification of the Diagnostic Performance of the EU-TIRADS Classification of Thyroid Nodules-Results of a Multicenter Study Performed in a Previously Iodine-Deficient Region

Background: To validate the European Thyroid Imaging and Reporting Data System EU-TIRADS classification in a multi-institutional database of thyroid nodules by analyzing the obtained scores and histopathology results. Methods: A total of 842 thyroid lesions (613 benign, 229 malignant) were identified in 428 patients (mean age 62.7 years) and scored according to EU-TIRADS, using ultrasound examination. In all tumors, histopathological verification was performed. Results: In EU-TIRADS 2 (154 nodules) all nodules were benign; in EU-TIRADS 3, only 3/93 malignancies were identified. In EU-TIRADS 4, 12/103 were malignant, and in EU-TIRADS 5 (278 benign vs. 214 malignant). The malignant nodules that would not have qualified for biopsy were: EU-TIRADS 3, 2/3 (67%) malignancies were <20 mm, in EU-TIRADS 4, 7/12 (58%) were <15 mm. In EU-TIRADS 5, 72/214 (34%) were <10 mm; in total, 81/229 (36%) malignant lesions would have been missed. The cutoff between EU-TIRADS 3/4 had sensitivity of 100%, specificity of 25.1%. Using cutoff for EU-TIRADS 5, 93.4%, 54.6%, respectively. Conclusion: The application of EU-TIRADS guidelines allowed us to achieve moderate specificity. The vast majority of malignancies in EU-TIRADS 3, 4, and 5 would not have been recommended for biopsy because having a smaller size than that proposed classification.

Neonatal TSH levels in Northern Ireland from 2003 to 2014 as a measure of population iodine status

OBJECTIVE

The re-emergence of iodine deficiency in the UK has recently been reported in a large cohort of teenage girls including from Northern Ireland (NI) using the gold standard spot urinary iodine concentration. We wished to explore and confirm this by analysing neonatal thyroid-stimulating hormone (nTSH) levels in the NI population.

DESIGN

We analysed the nTSH heel prick tests results from the NI national screening database between 2003 and 2014. The WHO proposes a definition for population iodine sufficiency at <3% of the population with nTSH results >5 mIU/L.

METHODS

Anonymized results from 288 491 nTSH tests were retrieved, and prevalence rates of results at increasing cut-offs including >2 mIU/L and >5 mIU/L calculated. We also assessed for possible seasonal variation in nTSH results.

RESULTS

An overall population prevalence of 0.49% with TSH >5 mIU/L was found, indicating population iodine sufficiency with no year attaining a prevalence >3%. The prevalence of nTSH >2 mIU/L decreased to 4.1% in 2007 and subsequently increased to 9.8% in 2014. Modest seasonal variation was also detected, with higher levels among April/May births.

CONCLUSIONS

The neonatal TSH database suggests iodine sufficiency in the NI population. However, the rising frequency of results >2 mIU/L may indicate an emerging mild iodine deficiency. This is one of the largest and longest studies of its kind in the UK and the first carried out in NI. The summer months may be a time of increased risk of iodine deficiency in our pregnant women whose requirements are increased and who are not currently targeted by any iodine fortification programme in the UK.

Has iodized salt reduced iodine-deficiency disorders among school-aged children in north-west Iran? A 9-year prospective study

OBJECTIVE

Low iodine intakes are associated with goitre and other iodine-deficiency disorders (IDD) that have affected billions of people worldwide. We aimed to assess total goitre rate (TGR) and urinary iodine concentration (UIC) in schoolchildren between 2007 and 2015, percentage of iodized salt consumption by households, and salt iodine content at production, distribution and household levels in north-west Iran. Design/Setting/Subjects UIC assessed among schoolchildren in nine consecutive years; 240 schoolchildren aged 8-10 years selected by systematic random sampling each year in the West Azerbaijan Province.

RESULTS

Median UIC was >100 μg/l in all years. More than 50 % of children had iodine deficiency (UIC≤99 μg/l) in 2010 and 2011, while this rate was approximately 15-35 % in other years. Proportion with UIC below 50 μg/l was <20 % in all years except 2010 and 2011. Excessive UIC (≥300 μg/l) rate was between 5·4 and 27·5 %. TGR decreased from 44 % in 1996 to 7·6 % and 0·4 % in 2001 and 2007, respectively. Regular surveys from 2002 to 2015 showed that 98 % or more of households consumed iodized salt. Iodine level ≥20 ppm was observed in 87·5, 83 and 73 % of salt at production, distribution and household level, respectively (data from national study in 2007). The last national study in 2014 showed that median iodine level in household salt was 27 ppm.

CONCLUSIONS

Our focused data suggest that the universal salt iodization programme is improving the iodine status of schoolchildren in the West Azerbaijan Province of Iran. Reduction of TGR to less than 5 % in schoolchildren indicates successful elimination of IDD as a major public health problem.

Iodine concentration of milk-alternative drinks available in the UK in comparison with cows' milk

Iodine deficiency is present in certain groups of the UK population, notably in pregnant women; this is of concern as iodine is required for fetal brain development. UK milk is rich in iodine and is the principal dietary iodine source. UK sales of milk-alternative drinks are increasing but data are lacking on their iodine content. As consumers may replace iodine-rich milk with milk-alternative drinks, we aimed to measure the iodine concentration of those available in the UK. Using inductively coupled plasma-MS, we determined the iodine concentration of seven types of milk-alternative drink (soya, almond, coconut, oat, rice, hazelnut and hemp) by analysing forty-seven products purchased in November/December 2015. For comparison, winter samples of conventional (n 5) and organic (n 5) cows' milk were included. The median iodine concentration of all of the unfortified milk-alternative drinks (n 44) was low, at 7·3 μg/kg, just 1·7 % of our value for winter conventional cows' milk (median 438 μg/kg). One brand (not the market leader), fortified its soya, oat and rice drinks with iodine and those drinks had a higher iodine concentration than unfortified drinks, at 280, 287 and 266 μg/kg, respectively. The iodine concentration of organic milk (median 324 μg/kg) was lower than that of conventional milk. Although many milk-alternative drinks are fortified with Ca, at the time of this study, just three of forty-seven drinks were fortified with iodine. Individuals who consume milk-alternative drinks that are not fortified with iodine in place of cows' milk may be at risk of iodine deficiency unless they consume alternative dietary iodine sources.

First Israeli National Iodine Survey Demonstrates Iodine Deficiency Among School-Aged Children and Pregnant Women

BACKGROUND

National data on iodine status in Israel are lacking. Reliance on iodine-depleted desalinated water, the absence of a salt iodization program, and reports of increased use of thyroid medication in Israel suggest that the population's iodine intake is likely inadequate. The aims of this study were therefore to determine the iodine status of Israeli school-age children (SAC) and pregnant women (PW) in a nationally representative sample obtained by a novel approach of using pre-discard urinalysis samples collected from a centralized national laboratory.

METHODS

Spot urine samples from 1023 SAC and 1074 PW, representing all regions and major sectors in Israel, were collected during 2016 at the Maccabi Healthcare Services central laboratory. Urinary iodine concentration (UIC) was measured, and the results were analyzed by trimester, sex, region, and sector.

RESULTS

SAC were iodine deficient, with a median (interquartile range [IQR]) UIC of 83 μg/L (52-127 μg/L); 62% of SAC UICs were below the World Health Organization adequacy range for SAC (100-199 μg/L). PW were also iodine deficient, with a median (IQR) UIC of 61 μg/L (36-97 μg/L); 85% of PW UICs were below the adequacy range for PW (150-249 μg/L). For both SAC and PW, the median UIC was below the World Health Organization's adequacy range across all sectors, sexes, and districts. Among SAC, the median (IQR) UIC was lower among females (75 μg/L; 48-119 μg/L) than males (92 μg/L; 59-133 μg/L; p < 0.05). Median UIC values of PW correlated significantly with the median UIC for SAC by sub-district (R² = 0.3, p < 0.05).

CONCLUSIONS

Urine sampling via a centralized national laboratory was efficient and cost-saving. Iodine deficiency in Israeli SAC and PW is a serious public-health concern. A national program of salt iodization and iodine supplementation of PW should be urgently considered.

Iodine Status and Iodised Salt Consumption in Portuguese School-Aged Children: The Iogeneration Study

The World Health Organization promotes salt iodisation to control iodine deficiency. In Portugal, the use of iodised salt in school canteens has been mandatory since 2013. The present study aimed to evaluate iodine status in school-aged children (6-12 years) and to monitor the use of iodised salt in school canteens. A total of 2018 participants were randomly selected to participate in a cross-sectional survey in northern Portugal. Children's urine and salt samples from households and school canteens were collected. A lifestyle questionnaire was completed by parents to assess children's eating frequency of iodine food sources. Urinary iodine concentration (UIC) was measured by inductively coupled plasma-mass spectrometry. The median UIC was 129 µg/L which indicates the adequacy of iodine status and 32% of the children had UIC < 100 µg/L. No school canteen implemented the iodised salt policy and only 2% of the households were using iodised salt. Lower consumption of milk, but not fish, was associated with a higher risk of iodine deficiency. Estimation of sodium intake from spot urine samples could be an opportunity for adequate monitoring of population means. Implementation of iodine deficiency control policies should include a monitoring program aligned with the commitment of reducing the population salt intake.