A systematic review and meta-analysis of 24-h urinary output of children and adolescents: impact on the assessment of iodine status using urinary biomarkers

Exposure risk assessment of di(2-ethylhexyl)phthalate (DEHP) using human population pharmacokinetic modeling of DEHP and its major in vivo metabolites

Di(2-ethylhexyl)phthalate (DEHP) is widely used as a plasticizer and is associated with potential adverse health effects, including endocrine disruption and organ toxicity. Accurate assessment of DEHP exposure risks requires robust pharmacokinetic models capable of capturing inter-individual variability and integrating human biomonitoring data. This study aimed to develop and validate a population pharmacokinetic model for DEHP and its major metabolites, mono(2-ethylhexyl)phthalate (MEHP), 2-ethyl-5-hydroxy-hexylphthalate (5-OH MEHP), and 2-ethyl-5-oxo-hexylphthalate (5-Oxo MEHP), to quantitatively assess DEHP exposure risks in human populations. Clinical data from DEHP-d4, a radiolabeled DEHP isotope, were used to construct a pharmacokinetic model using non-linear mixed effects modeling. The model incorporated plasma concentration and urinary excretion data for DEHP and its metabolites. Biomonitoring data were integrated using reverse dosimetry to estimate external exposure levels, and margins of safety were then calculated by comparing these estimates with established reference doses. The model demonstrated robust correlations (R2 > 0.99) between external DEHP exposure and internal biomarker levels. Predicted external exposure levels ranged from 0.52 to 157.52 µg/kg/day, with margins of safety varying between 0.13 and 38.17. Despite substantial inter-individual variability, the model accurately captured population-level pharmacokinetic diversity and provided reliable risk assessments. The developed pharmacokinetic model offers a versatile tool for integrating biomonitoring data and conducting rapid, population-specific DEHP risk assessments. These findings underscore the importance of ongoing monitoring and stringent regulatory measures to mitigate DEHP-associated health risks.

Urinary Caffeine Levels in Chinese Children: Insights from Diet, Gender, and Regional Variations

BACKGROUND/OBJECTIVES

The consumption of caffeine products among children in China is on the rise, yet there remains a paucity of evidence regarding the variability of caffeine consumption and the influencing factors. Urinary caffeine levels provide a valid indicator of caffeine intake, as it directly reflects the quantitative measure of consumption within the population. This study aimed to investigate the effects of diet, gender, and region on urinary caffeine concentrations in Chinese children and their parents, specifically focusing on participants from Guangdong province and Guangxi province.

METHODS

Morning urine samples were pretreated using liquid-liquid extraction. Caffeine and creatinine concentrations were analyzed using ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-MS/MS), with quality control measures ensuring method accuracy (recovery rate: 92.8-122%, RSD < 20%). Caffeine exposure was assessed through estimated daily intake (EDI) calculations, and statistical analyses, including weighted regression and Spearman correlation, were conducted to evaluate associations with demographic and dietary variables.

RESULTS

The findings revealed that urinary caffeine levels and detection rates among Chinese children were significantly lower than those observed in the United States (30.1 ng/mL), with a median concentration of 2.18 ng/mL and a detection rate of 45%. Urinary caffeine concentrations in males were slightly higher than in females; however, these gender differences were not statistically significant. Certain dietary habits, particularly milk consumption, were found to influence urinary caffeine levels and detection rates. Using the random forest method, urine caffeine detection was highest (nearly 60%) when milk was consumed three times a week. Regionally, children in Guangdong had marginally higher urinary caffeine concentrations compared to those in Guangxi (median: 5.20 μg/gcrea vs. 1.58 μg/gcrea). The estimated daily caffeine intake suggested that children in China consume less caffeine than their counterparts in other countries.

CONCLUSIONS

These results indicate that dietary habits significantly correlated with caffeine consumption in children, and urinary caffeine concentration serves as a valuable measure for dietary research.

Urinary paraben concentrations among children from the northernmost of Thailand: Cross-sectional study for exposure and health risks

Parabens are widely used as antimicrobial preservatives in foods, personal care, cosmetics, and pharmaceutical products. The metabolization of parabens in the human body is excreted via urine in free plus conjugated forms. Currently, the prevalent use of parabens has increased alarms about health risks linked with endocrine disrupting effects. A cross-sectional study was used to gather information from participants in Chiang Rai province. The purposes of the study are to investigate paraben concentrations in urine, to analyze the correlation of urinary parabens, and to assess health risks among children in pre-schools and primary schools. Overall, 140 first morning void urine samples were collected and measured by LC-MS/MS to determine methyl paraben (MeP), ethyl paraben (EtP), and propyl paraben (PrP). The detection rate and geometric mean without adjusting and adjusting urine specific gravity of MeP, EtP, and PrP in overall samples were (100.00 %; 27.94 µg/L; 30.14 µg/L), (46.43 %; 0.77 µg/L; 0.83 µg/L), and (97.86 %; 2.80 µg/L; 3.02 µg/L), respectively. Almost three urinary paraben concentrations in pre-schools were higher than in primary schools. The highest significant positive correlation of parabens (p < 0.01) was MeP and PrP both in pre-schools and primary schools. The geometric mean of estimated daily intake (EDI urine) for MeP, EtP, and PrP were 6.27, 0.22, and 1.09 µg/kg-bw/day, respectively. The estimated daily intake and health risks indicated PrP led to potential human health risks at 5.70 % of overall samples. Additionally, Thai children are widely exposed to parabens and relatively higher PrP and MeP exposure than the concentration reported in several countries. This is the first study assessing urinary parabens in Thailand. The finding demonstrates that children's exposure to parabens in the study areas would impact their health, so there should be confirmation for further management.

Occurrence and Exposure Assessment of Zearalenone in the Zhejiang Province, China

This study aims to examine the hazards of zearalenone (ZEN) to humans and assess the risk of dietary exposure to ZEN, particularly in relation to precocious puberty in children from the Zhejiang Province. The test results from five types of food from the Zhejiang Province show that corn oil has the highest detection rate of 87.82%. The levels of ZEN do not exceed the existing safety standards in any sample investigated in this study. According to the data from the Food Consumption Survey of Zhejiang Province residents, rice is the primary source of ZEN exposure, accounting for 55.85% of total exposure among all age groups. Based on the 50th exposure percentile, it would take 6.25 years of rice consumption to reach 1 year of safe ZEN exposure. Overall, the majority of the residents in the Zhejiang Province have a low risk of exposure to ZEN. In an extreme case (based on the 95th exposure percentile), the total ZEN exposure from the studied foods with respect to children aged ≤6 years and 7-12 years is 0.38 μg/kg b.w. and 0.26 μg/kg b.w., respectively-both exceeding the safety limit of 0.25 μg/kg b.w. set by the European Food Safety Authority, indicating a potential risk of exposure. Precocious puberty assessments show that ZEN exposure levels in children in the Zhejiang Province are significantly lower than those associated with precocious puberty; thus, precocious puberty is unlikely to occur in this area. Given ZEN's estrogenic effect, it is necessary to monitor the level of ZEN in different food items, revise the relevant standards as needed, and focus on exposure to ZEN in younger age groups.

Widespread occurrence of glyphosate and aminomethylphosphonic acid in indoor dust from urban homes across the United States and its contribution to human exposure

Glyphosate is the most widely used herbicide worldwide, with concerns over human exposure and potential health risks. Nevertheless, little is known about the sources of human exposure to glyphosate and its degradation product, aminomethylphosphonic acid (AMPA). In this study, we measured glyphosate and AMPA in 99 indoor dust samples collected from urban homes in sixteen states in the USA. Glyphosate and AMPA were detected in all samples at geometric mean (GM) concentrations of 193 and 30.8 ng/g, respectively. We found a strong and significant positive correlation between glyphosate and AMPA concentrations (r = 0.70, p < 0.01), indicating that the latter mainly originated from glyphosate. The concentrations of glyphosate (r = 0.40, p < 0.01) and AMPA (r = 0.33, p < 0.01) in indoor dust were significantly correlated with the county-wide agricultural usage of this herbicide. Human exposure to glyphosate and AMPA through dust ingestion were in the ranges of 0.05-0.85 and 0.01-0.14 ng/kg body weight (BW)/day, respectively, for various age groups, which were more than two orders of magnitude below the acceptable daily intake for glyphosate (500 μg/kg BW/day). Further studies are needed to identify the sources and health outcomes of human exposure to glyphosate.

Thyroid function and iodine intake: global recommendations and relevant dietary trends

Iodine is a micronutrient that is essential for thyroid hormone production. Adequate iodine intake is especially important during pregnancy and early life, when brain development is dependent on thyroid hormones. Iodine intake recommendations vary around the world, but most recommendations generally reflect the increased requirements during pregnancy and lactation, although adequate iodine intake before pregnancy is also important. Tremendous progress has been made in improving iodine intake across the world over the past 30 years, mainly through salt-iodization programmes. However, in countries without strong iodine fortification programmes, and with shifts in dietary patterns, a need has arisen for health organizations, governments and clinicians to ensure that adequate iodine is consumed by everyone in the population. For example, in countries in which adequate iodine intake depends on individual food choice, particularly of iodine-rich milk and dairy products, intake can be highly variable and is also vulnerable to changing dietary patterns. In this Review, iodine is considered in the wider context of the increasing prevalence of overweight and obesity, the dietary trends for salt restriction for cardiovascular health and the increasing uptake of plant-based diets.

Pregnant women at risk for iodine deficiency but adequate iodine intake in school-aged children of Zhejiang Province, China

The median urinary iodine concentration (UIC) of school-aged children has been commonly used as a surrogate to assess iodine status of a population including pregnant women. However, pregnant women have higher iodine requirements than children due to increased production of thyroid hormones. The aim of the study was to evaluate the iodine status of pregnant women and children as well as their household salt iodine concentration (SIC) in Quzhou, Zhejiang Province, China. Eligible pregnant women and children from all six counties of Quzhou in 2021 were recruited into the study. They were asked to complete a socio-demographic questionnaire and provide both a spot urine and a household table salt sample for the determination of UIC and SIC. A total of 629 pregnant women (mean age and gestation weeks of 29.6 years and 21.6 weeks, respectively) and 1273 school-aged children (mean age of 9 years and 49.8% of them were females) were included in the study. The overall median UIC of pregnant women and children in our sample was 127 (82, 193) μg/L and 222 (147, 327) μg/L, respectively, indicating sufficient iodine status in children but a risk of mild-to-moderate iodine deficiency in pregnant women. Distribution of iodine nutrition in children varied significantly according to their sex and age (P < 0.05). The rate of adequately household iodised salt samples (18-33 mg/kg) provided by pregnant women and children was 92.4% and 90.6%, respectively. In conclusion, our results indicated a risk of insufficient iodine status in pregnant population of China, but iodine sufficiency in school-aged children. Our data also suggested that median UIC of children may not be used as a surrogate to assess iodine status in pregnant women.

Iodine intake in the Swiss population 100 years after the introduction of iodised salt: a cross-sectional national study in children and pregnant women

PURPOSE

The Swiss voluntary salt iodisation programme has successfully prevented iodine deficiency for 100 years, but dietary habits are changing and today only one-third of processed foods contain iodised salt. We aimed to monitor the current iodine status in children and pregnant women.

METHODS

We conducted a nationwide cross-sectional study in children (6-12 years) and pregnant women and measured the urinary iodine concentration (UIC) in spot urine samples. We estimated the iodine intake using UIC and urinary creatinine concentration (UCC) and determined the prevalence of intakes below the average requirement (AR) using the SPADE method. We measured dried blood spot (DBS) thyroglobulin (Tg), TSH and total T4 in pregnant women.

RESULTS

The median UIC was 127 μg/L (bootstrapped 95% CI 119, 140, n = 362) in children and 97 μg/L (bootstrapped 95% CI 90, 106, n = 473) in pregnant women. The estimated prevalence of inadequate iodine intake (< 65 μg/day) was 5.4% (bootstrapped 95% CI 0.0, 14.6) in children. Half (47%) of the women consumed iodine-containing multivitamin and mineral supplements (≥ 150 μg/day). Compared to non-users, users had higher median UIC (129 vs. 81 μg/L, P < 0.001), lower prevalence of inadequacy (< 160 μg/day; 0.2 vs. 31%) and lower DBS-Tg (23 vs. 29 μg/L, P < 0.001). All women were euthyroid.

CONCLUSIONS

The Swiss diet and current salt fortification provides adequate iodine intake in children, but not in all pregnant women. Iodine supplements cover the dietary gap in pregnancy but are not universally consumed. Therefore, improved use of iodised salt in processed foods is desired to ensure adequate iodine intake in all population groups. This trial was registered at clinicaltrials.gov as NCT04524013.

Urine Se concentration poorly predicts plasma Se concentration at sub-district scales in Zimbabwe, limiting its value as a biomarker of population Se status

Introduction

The current study investigated the value of urine selenium (Se) concentration as a biomarker of population Se status in rural sub-Saharan Africa.

Method

Urine and plasma Se concentrations were measured among children aged 6-59 months (n = 608) and women of reproductive age (WRA, n = 781) living in rural Zimbabwe (Murehwa, Shamva, and Mutasa districts) and participating in a pilot national micronutrient survey. Selenium concentrations were measured by inductively coupled plasma-mass spectrometry (ICP-MS), and urine concentrations were corrected for hydration status.

Results

The median (Q1, Q3) urine Se concentrations were 8.4 μg/L (5.3, 13.5) and 10.5 μg/L (6.5, 15.2) in children and WRA, respectively. There was moderate evidence for a relationship between urine Se concentration and plasma Se concentration in children (p = 0.0236) and WRA (p = < 0.0001), but the relationship had poor predictive value. Using previously defined thresholds for optimal activity of iodothyronine deiodinase (IDI), there was an association between deficiency when indicated by plasma Se concentrations and urine Se concentrations among WRA, but not among children.

Discussion

Urine Se concentration poorly predicted plasma Se concentration at sub-district scales in Zimbabwe, limiting its value as a biomarker of population Se status in this context. Further research is warranted at wider spatial scales to determine the value of urine Se as a biomarker when there is greater heterogeneity in Se exposure.

Accuracy of equations for predicting 24-h urinary potassium excretion from spot urine samples in Chinese children

Accurate assessments of potassium intake in children are important for the early prevention of CVD. Currently, there is no simple approach for accurate estimation of potassium intake in children. We aim to evaluate the accuracy of 24-h urinary potassium excretion (24UKV) estimation in children using three common equations: the Kawasaki, Tanaka and Mage formulas, in a hospital-based setting. A total of 151 participants aged 5-18 years were initially enrolled, and spot urine samples were collected in the whole 24-h duration to measure the concentrations of potassium and creatinine. We calculated the mean difference, absolute and relative difference and misclassification rate between measured 24UKV and the predicted ones using Kawasaki, Tanaka and Mage formulas in 129 participants. The mean measured 24UKV was 1193·3 mg/d in our study. Mean differences between estimated and measured 24UKV were 1215·6, -14·9 and 230·3 mg/d by the Kawasaki, Tanaka and Mage formulas, respectively. All estimated 24UKV were significantly different from the measured values in all the time point (all P < 0·05), except for the predicted values from Tanaka formula using morning, afternoon and evening spot urine. The proportions with relative differences over 40 % were 87·2%, 32·5% and 47·3 % for Kawasaki, Tanaka and Mage formulas, respectively. Misclassification rates were 91·5 % for Kawasaki, 44·4 % for Tanaka and 58·9 % for Mage formula at the individual level. Our findings showed that misclassification could occur on the individual level when using Kawasaki, Tanaka and Mage formulas to estimate 24UKV from spot urine in the child population.

Urinary sodium, iodine, and volume in relation to metabolic syndrome in Mesoamerican children and their parents

BACKGROUND AND AIMS

The roles of sodium or iodine intake on the metabolic syndrome (MetS) etiology remain controversial. We evaluated the associations of 24 h urinary sodium and iodine with MetS among Mesoamerican children and their adult parents.

METHODS AND RESULTS

We conducted a cross-sectional study among 217 school-age children and 478 parents from 9 Mesoamerican cities. Exposures were high 24 h urinary sodium excretion and concentration (>2000 mg/d or mg/L, respectively) and high 24 h urinary iodine excretion and concentration (≥300 μg/d or μg/L, respectively). In children, the outcome was a standardized metabolic score from five criteria analogous to the Adult Treatment Panel (ATP) III criteria. In adults, MetS was defined according to the ATP III criteria. We estimated adjusted mean differences in the metabolic risk score and adjusted prevalence ratios of MetS between exposure categories using multivariable regression. In children, high sodium concentration was associated with a 0.10 units (43% of a SD) higher score (P = 0.001) and high iodine concentration was related to a 0.09 units (39% of a SD) higher score (P = 0.009). Unexpectedly, high 24 h urinary volume was associated with a lower metabolic score. In adults, high 24 h sodium excretion was related to hypertension and high iodine concentration was related to increased MetS prevalence.

CONCLUSION

High sodium and iodine concentrations, but not 24 h iodine excretion, are significantly associated with MetS in children, whereas high 24 h urinary volume is related to a decreased metabolic score. In adults, high iodine concentration tends to be related to increased MetS prevalence, but not 24 h iodine excretion.

Iodine Status of Mother-Infant Dyads from Montréal, Canada: Secondary Analyses of a Vitamin D Supplementation Trial in Breastfed Infants

BACKGROUND

Most pregnant or lactating women in Canada will not meet iodine requirements without iodine supplementation.

OBJECTIVES

To assess the iodine status of 132 mother-infant pairs based on secondary analyses of a vitamin D supplementation trial in breastfed infants from Montréal, Canada.

METHODS

Maternal iodine status was assessed using the breastmilk iodine concentration (BMIC). Singleton, term-born infants were studied from 1-36 months of age. Usual (adjusted for within-person variation) iodine intakes were estimated from urinary iodine and creatinine concentrations. Iodine status was assessed using median urinary iodine concentrations (UICs) and by estimating inadequate intakes by the cut-point method using a proposed Estimated Average Requirement for infants 0-6 months of age (72 μg/d).

RESULTS

At 1, 3, and 6 months of age, 70%, 63%, and 3% of infants, respectively, were exclusively breastfed. From 1-36 months of age (n = 82-129), the median UICs were ≥100 μg/L (range, 246-403 μg/L), which is the cutoff for adequate intakes set by the WHO for children <2 years. Almost all (98%-99%) infants at 1 and 2 months, 2 and 3 months, and 3 and 6 months of age had usual creatinine-adjusted iodine intakes ≥ 72 μg/d. The median BMIC was higher (P < 0.001) at 1 month compared to 6 months of lactation [1 month, 198 μg/kg (IQR, 124-274; n = 105) and 6 months, 109 μg/kg (IQR, 67-168; n = 78)]. At 1 and 6 months, 96% and 79% of mothers, respectively, had a BMIC ≥ 60 μg/kg, the lower limit of a normal reference range. The percentages of mothers that used a multivitamin-mineral (MVM) supplement containing iodine were 90% in pregnancy and 79% and 59% at 1 and 6 months of lactation, respectively.

CONCLUSIONS

The iodine status of infants was adequate throughout infancy. These results support a recommendation that all women who could become pregnant, who are pregnant, or who are breastfeeding take a daily MVM supplement containing iodine.

OUP accepted manuscript

Context

Adequate iodine intake is essential throughout life. Key dietary sources are iodized salt and animal products, but dietary patterns in Europe are changing, for example toward lower salt intake and a more plant-based diet.

Objective

To review iodine intake (not status) in European populations (adults, children, and pregnant women) to identify at-risk groups and dietary sources.

Data sources

PubMed, Embase, and Cochrane databases, as well as European national nutrition surveys were searched for data on had iodine intake (from dietary assessment) and sources of iodine, collected after 2006.

Data selection

In total, 57 studies were included, comprising 22 national surveys and 35 sub-national studies. Iodine intake data were available from national surveys of children aged <10 years (n = 11), 11–17 years (n = 12), and adults (n = 15), but data from pregnancy were only available from sub-national studies.

Results

Iodine intake data are lacking—only 17 of 45 (38%) European countries had iodine-intake data from national surveys. Iodine intake reported from national surveys was below recommendations for: (1) children aged <10 years in 2 surveys (18%), (2) boys and girls aged 11–17 years in 6 (50%) and 8 (68%) surveys, respectively, and (3) adult men and women in 7 (47%) and 12 (80%) surveys, respectively. In pregnant women, intake was below recommendations except where women were taking iodine-containing supplements. Just 32% of national surveys (n = 7) included iodized salt when estimating iodine intake. Milk, dairy products, fish, and eggs were important contributors to intake in many countries, suggesting limited sources in plant-based diets.

Conclusion

Results are limited by the challenges of dietary assessment for measuring iodine intake. Future national surveys should include iodine intake. Policy makers should consider dietary sources alongside any iodized salt policies when considering methods for improving population iodine intake.

Systematic Review Registration

PROSPERO 2017 CRD42017075422.

Association of Salt Iodization and Urine Iodine Concentration in Schoolchildren from Public Schools in Northeast of Brazil

Iodine deficiency (ID) is recognized as a leading risk factor for child development. Universal salt iodization (USI) is an effective and well-established intervention strategy for the prevention of iodine deficiency disorders (IDD). To evaluate the levels of iodine in household salt samples and the urinary iodine concentration (UIC) in schoolchildren aged 6 to 14 years in public schools in Bahia, Brazil. A cross-sectional study was conducted with 1231 students (6 to 14 years old) from 17 public schools in Bahia. The iodine concentration was evaluated in salt and UIC samples. The adapted Sandell-Kolthoff reaction was used to determine urinary iodine levels. A spectrophotometer (UV-Vis) was used to examine the reduction of ceric ammonium sulfate. A standard iodine solution using a potassium iodate was used to extrapolate the iodine concentrations. The total of 665 salt samples had a median iodine concentration of 24 mg/kg (25th-75th percentile 17.0 to 28.5 mg/kg). The largest proportion (79.6%) of salt samples had iodine concentration in the recommended range, 17.6% of the samples presented iodine at a salt concentration below the established level (<15 mg/kg) and a small proportion was above it (2.8%). The general mean urinary iodine concentration (MUIC) was 217.53 ± 28.30 μg/L and median was 205.50 μg/L. The students evaluated and the salt samples analyzed showed satisfactory results, as recommended by Brazilian legislation and nutritional recommendations of the World Health Organization (WHO).

Neonatal heel prick screening TSH concentration in the Netherlands as indicator of iodine status

Background

Neonatal Thyroid Stimulating Hormone (nTSH) is proposed as indicator of iodine deficiency in a population. Population’s iodine sufficiency is indicated by a proportion of the newborns less than 3% having nTSH above 5 mIU/L. The aim of this study was to explore the Dutch neonatal heel prick screening TSH data to assess iodine status in the Netherlands and identify determinants and potential confounders of this assessment.

Methods

All newborns born in the Netherlands between 2007 and 2015 with a heel prick collection at day 3-7 were included (n = 1,435,600), except preterm neonates and baby’s with a low birth weight. Total T4 was measured for all children, nTSH was measured in the ~ 20% children with lowest total T4.

Results

The proportion with nTSH > 5mIU/L fluctuated between 0.6-1.3% in 2007-2015. nTSH was significantly associated with laboratory performing the nTSH assay and age of heel prick sampling. The overall increasing trend in proportion nTSH >1mIU/L was confounded by the laboratories with different and changed assays.

Conclusions

The low proportion neonates with high nTSH suggests a sufficient iodine status in the Netherlands. Whether the increased proportion nTSH>1mIU/L over the years is an early indicator of deterioration of the iodine status remains unclear, due to differences and changes in analytical assays. nTSH might be a valuable and inexpensive way to get crude insight in the (trend in) iodine status, but more research is needed on the validity and potential conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12937-021-00722-4.