A child's silhouette filled with an iodized salt shaker landscape, against a backdrop of a concerned thyroid gland symbolizing iodine deficiency.

Iodine Levels in Kids: Are We Losing Ground?

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Jordan Keane in Health & Wellness October 2026 • 4 min read.

"A new study from Brazil raises concerns about a potential resurgence of iodine deficiency in schoolchildren after a decade of progress."


Iodine is an essential nutrient, critical for thyroid hormone production, which in turn regulates growth and metabolism. Without enough iodine, the thyroid can't function properly, leading to a range of health problems, especially in children. These problems can include goiter (an enlarged thyroid gland), hypothyroidism (underactive thyroid), and impaired cognitive development.

For decades, public health initiatives have focused on ensuring adequate iodine intake, primarily through iodized salt. These programs have been largely successful in reducing iodine deficiency worldwide. However, maintaining this success requires constant monitoring and adaptation, as dietary habits and food policies can change.

Now, a new study is casting doubt on whether those gains are sustainable. Researchers in Brazil have found that iodine levels in schoolchildren are dropping, raising concerns about a potential resurgence of deficiency.

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The Scope of Iodine Deficiency in Children

Iodine deficiency remains a significant global public health concern, particularly affecting children's cognitive development and overall health. While comprehensive recent statistics are still being gathered, health organizations continue to monitor iodine status across different populations. The effects of iodine deficiency on children's brain development and intellectual capacity have been documented in numerous studies worldwide, though the exact prevalence varies by region and dietary habits.

Monitoring Iodine Status: Schoolchildren as Sentinels

Schoolchildren have traditionally been used as sentinel populations for monitoring iodine nutritional status, though this approach has recognized limitations. The WHO has established guidelines for assessing iodine deficiency disorders, with school-age children serving as the primary target group for surveillance. While gross effects like goiter were recognized over a century ago, the full spectrum of iodine deficiency disorders affecting all age groups was only emphasized in the late twentieth century. Urinary iodine concentration remains a key biomarker, though its interpretation requires consideration of recent iodine intake and individual variation.

A Century of Understanding Iodine's Role

Iodine is essential for thyroid hormone synthesis, which regulates metabolism, growth, and development. Iodine deficiency causes adverse health effects across the lifespan, but is particularly problematic during pregnancy when it can lead to irreversible fetal brain damage. High prevalence of severe iodine deficiency, manifesting as endemic goiter and cretinism, predated modern intervention efforts. The elimination of iodine deficiency disorders represents one of the great public health achievements of the twentieth century, particularly in the Americas where dramatic progress has been documented.

The Brazilian Study: A Closer Look

A child's silhouette filled with an iodized salt shaker landscape, against a backdrop of a concerned thyroid gland symbolizing iodine deficiency.

Researchers from the University of Ribeirão Preto and the Faculty of Medicine of Ribeirão Preto USP conducted a study comparing iodine concentrations in kitchen salt and urine samples from schoolchildren in 2007 and 2015. They also assessed thyroid volume through palpation. The study aimed to evaluate the impact of changes in salt iodization regulations in Brazil, which reduced the amount of iodine allowed in salt for domestic consumption from 20-60 mg/kg to 15-45 mg/kg in 2013.

Here's a breakdown of what they found:

  • Declining Iodine Levels: Urinary iodine concentrations in schoolchildren decreased significantly between 2007 and 2015.
  • Increase in Goiter Prevalence: The prevalence of goiter, an enlarged thyroid gland often caused by iodine deficiency, increased in one of the schools studied.
  • Variability in Salt Iodization: While salt samples in 2015 were more uniform in iodine content compared to 2007, some children still had iodine levels below the recommended threshold.
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Recent Developments in Iodine Research

Scientific understanding of iodine's role in child development continues to evolve through ongoing research and systematic reviews. Researchers are examining the relationships between iodine status, dietary patterns, and cognitive outcomes in various populations. New studies are employing more comprehensive assessment tools to evaluate the nuanced effects of iodine deficiency on children's intellectual functioning. The field continues to develop improved methodologies for measuring iodine status and its impacts on health outcomes.

Challenges in Iodine Deficiency Interventions

Despite significant progress, challenges remain in addressing iodine deficiency globally. Some regions still struggle with implementation of effective salt iodization programs, while others face issues of sustainability. The balance between addressing deficiency and preventing excessive iodine intake presents ongoing public health dilemmas. Economic constraints, cultural dietary practices, and supply chain issues continue to undermine iodine intervention programs in various parts of the world.

Cognitive Impacts Across Iodine Status Levels

Research comparing cognitive function across different iodine status levels has revealed important differences in children's intellectual capabilities. Studies using comprehensive cognitive assessment tools, including the complete Wechsler Intelligence Scale for Children, have documented how moderate iodine deficiency negatively impairs cognitive function in schoolchildren. The cognitive profile of children with moderate iodine deficiency shows several changes compared to their iodine-sufficient peers. These differences are particularly evident in perceptual reasoning and other cognitive domains, suggesting that mild to moderate deficiency may prevent children from reaching their full intellectual potential.

The study highlights a potential link between the change in salt iodization regulations and a decrease in iodine intake among schoolchildren. While the overall iodine intake of the students was generally satisfactory, individual iodine health was compromised, with some children showing urinary iodine levels lower than 100 µg/L and increased thyroid volumes.

What Does This Mean?

This study serves as a warning sign that we can't take the success of iodine fortification for granted. Constant monitoring and adaptation of public health strategies are crucial to ensure that future generations receive enough iodine for healthy development. Further research is needed to determine if this trend is isolated to Ribeirão Preto, or indicative of a broader problem. If the latter, adjustments to salt iodization levels and other interventions may be necessary.

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Expert Insights on Iodine Nutrition

Recent research has provided new insights into the prevalence and impact of iodine deficiency among children. National-level estimates indicate concerning rates of iodine deficiency in certain populations, with identification of predisposing dietary factors. Studies have also demonstrated that iodine supplementation can improve cognitive outcomes, particularly perceptual reasoning, in mildly iodine-deficient children. Experts suggest that even mild iodine deficiency may prevent children from attaining their full intellectual potential, underscoring the importance of adequate iodine nutrition during critical developmental periods.

Pathways Forward in Iodine Research

Future research will likely focus on more precise biomarkers and longitudinal studies to better understand iodine's impact across the lifespan. Advances in nutritional assessment technologies may enable more accurate monitoring of iodine status in populations. The development of innovative intervention strategies, including food fortification beyond salt, represents promising avenues for addressing persistent deficiency. Greater integration of iodine nutrition into broader public health frameworks may help sustain progress and address emerging challenges.

Global Perspectives on Iodine Disorders

According to the World Health Organization, iodine-deficiency disorders can start before birth and jeopardize children's mental health and survival. During neonatal period, childhood and adolescence, these disorders can lead to hypothyroidism and hyperthyroidism. Interestingly, research has also identified cases of excessive iodine status among school-aged children in certain regions, highlighting the complexity of iodine nutrition. The balance between preventing deficiency and avoiding excess requires careful attention to local dietary patterns, salt iodization levels, and other iodine sources.

Interventions That Make a Difference

Practical interventions have demonstrated the ability to improve iodine status and cognitive outcomes in deficient populations. Research on fortified iodine milk has shown promise in reducing iodine deficiency and supporting cognitive development among schoolchildren. School-based interventions represent an important delivery mechanism for improving iodine nutrition and food literacy related to iodine. The global burden of iodine deficiency continues to drive public health efforts, with researchers analyzing prevalence, incidence, and disability-adjusted life-year rates to guide resource allocation and intervention priorities.

What urine and thyroid measurements can show

Urinary iodine is useful for tracking recent iodine intake because much of the iodine absorbed is excreted in urine. It reflects current intake, rather than directly measuring thyroid function or size, so the urine results alone cannot establish thyroid effects in individual children.[1] [2]

A national median can look adequate while concealing differences between population groups or regions. It also combines iodine from all dietary sources, so it cannot by itself show how much salt iodization contributed.[3] [4]

Brazilian figures in a wider monitoring picture

Brazil’s national median urinary iodine concentration was 276.7 μg/L, with regional medians ranging from 248.0 μg/L in the South to 298.8 μg/L in the Northeast. The state medians spanned a wider range, from 169.3 μg/L in Amazonas to 361.0 μg/L in Rio Grande do Norte, underscoring how a national figure can obscure local variation.[3]

Other schoolchild samples provide different reference points: a municipality in the semi-arid region reported median urinary iodine levels of 150.8 μg/L in its urban population and 119.2 μg/L in its rural population, while Chinese samples reported medians of 185.14 μg/L and 226.4 μg/L. These are separate populations, not direct comparisons of the same children or conditions.[5] [6] [7]

Earlier Brazilian surveillance collected 16,803 urine samples, but only 7,702 could be matched to clinical records. That gap means the linked urine-and-clinical analysis represents a subset of the samples collected, rather than every child with a urine measurement.[8]

The available Brazilian evidence also has limits for comparing work across time and place: a national review included only seven studies, and reported iodine measurements used methods and units that were not always convertible. A separate assessment noted the lack of a recent national survey of household table-salt iodine and of continuous monitoring of overall population iodine status.[9] [10]

What remains unresolved about iodine status

  • Did the lower urinary iodine results in the 2015 comparison reflect the revised salt rules, or other changes in iodine sources? The urine measure reflects intake from recent dietary sources, while the national median does not isolate salt’s contribution.[1] [4] [11]
  • How closely do urine measurements correspond to thyroid changes in the children being monitored? Urinary iodine does not directly assess thyroid function or size.[2]

Sources

  1. Iodine deficiency (www.who.int)
  2. Urinary iodine concentration (UIC) could be a promising biomarker for predicting goiter among school-age children: A systematic review and meta-analysis (pmc.ncbi.nlm.nih.gov)
  3. Iodine Status of Brazilian School-Age Children: A National Cross-Sectional Survey (pmc.ncbi.nlm.nih.gov)
  4. ign.org (ign.org)
  5. Iodine Malnutrition and Associated Factors in Schoolchildren Aged 6 to 14 Years in a Municipality Situated in the Semi-Arid Region of the State of Minas Gerais, Brazil, 2008 (www.scirp.org)
  6. Iodine Nutritional Status and Related Factors among Chinese School-Age Children in Three Different Areas: A Cross-Sectional Study (pmc.ncbi.nlm.nih.gov)
  7. A Cross-Sectional Study of Iodine Nutritional Status Among School-Age Children in Chongqing, China (pmc.ncbi.nlm.nih.gov)
  8. [Endemic goiter prevalence survey in Brazilian schoolchildren 6 to 14 years old, 1994-1996]. (pubmed.ncbi.nlm.nih.gov)
  9. Brasil - Iodine nutritional status in Brazil: a meta-analysis of all studies performed in the country pinpoints to an insufficient evaluation and heterogeneity Iodine nutritional status in Brazil: a m (www.scielo.br)
  10. www.aem-sbem.com (www.aem-sbem.com)
  11. Comparison of Iodine Concentrations in Kitchen Salt and Urine with the Thyroid Volume of Schoolchildren from Ribeirão Preto, São Paulo, Brazil: Warning of Worsening After 10 Years of Study. (pubmed.ncbi.nlm.nih.gov)

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

Everything You Need To Know

1

Why is iodine important for children's health?

Iodine is crucial for children because it is essential for the production of thyroid hormones. These hormones regulate growth and metabolism. Without adequate iodine, children can develop goiter, experience hypothyroidism (underactive thyroid), and suffer impaired cognitive development. These health problems can have long-lasting effects on a child's physical and mental well-being, underscoring the importance of ensuring sufficient iodine intake.

2

What did the study in Ribeirão Preto, Brazil, reveal about iodine levels in schoolchildren?

The study conducted in Ribeirão Preto, Brazil, revealed a concerning decline in iodine levels among schoolchildren between 2007 and 2015. Researchers found that urinary iodine concentrations decreased significantly. Furthermore, the prevalence of goiter, an indicator of iodine deficiency, increased in one of the schools studied. These findings suggest a potential reversal of the progress made in iodine intake over the past decade in the region, prompting worries about the children's health.

3

How did changes in salt iodization regulations in Brazil impact iodine levels in schoolchildren?

The study in Ribeirão Preto examined the effect of altered salt iodization regulations in Brazil. In 2013, the amount of iodine allowed in salt for domestic consumption was reduced from 20-60 mg/kg to 15-45 mg/kg. The study suggests a link between this regulatory change and the observed decline in iodine levels among schoolchildren. While salt samples in 2015 were more uniform in iodine content, some children still had iodine levels below the recommended threshold. The study indicates the importance of maintaining the right iodine levels in salt to ensure children receive enough iodine.

4

What are the implications of declining iodine levels in schoolchildren, as seen in the study?

The decline in iodine levels among schoolchildren, as shown in the Ribeirão Preto study, raises several critical implications. Primarily, it signals a potential resurgence of iodine deficiency and its associated health risks. This includes the increased risk of goiter, hypothyroidism, and impaired cognitive development. This study serves as a warning that public health initiatives focusing on iodine fortification, like the use of iodized salt, need continuous monitoring and adjustments to maintain their effectiveness. If the trend observed in Ribeirão Preto extends to other regions, modifications to salt iodization and other public health interventions may become necessary.

5

How can we ensure that children receive enough iodine for healthy development, given the study's findings?

To ensure children receive enough iodine, a multi-faceted approach is needed, as suggested by the study's implications. Constant monitoring of iodine levels in the population, particularly in schoolchildren, is crucial. This requires regular assessments of urinary iodine concentrations and thyroid health. Adjustments to salt iodization regulations may be necessary to ensure adequate iodine intake through this primary source. Furthermore, public health strategies should be adapted to address specific dietary habits and any changes in food policies that could affect iodine intake. Education campaigns about the importance of iodine-rich foods or iodine supplementation may also play a role, especially if iodine levels are significantly compromised.

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