Iodine Levels in Kids: Are We Sliding Backwards?
"A Brazilian study raises concerns about iodine intake among schoolchildren, highlighting the need for ongoing monitoring and adjustments to salt iodization programs."
Iodine is a trace element crucial for thyroid hormone production. These hormones regulate metabolism, growth, and development, especially in the brain. A deficiency can lead to a range of health problems, from goiters (enlarged thyroid glands) to impaired cognitive function, particularly in children.
For decades, universal salt iodization has been a cornerstone of public health efforts to combat iodine deficiency. By adding iodine to table salt, a readily accessible food item, populations worldwide have seen a dramatic reduction in iodine-related disorders.
However, a recent study conducted in Ribeirão Preto, São Paulo, Brazil, suggests that this progress may be stalling. The research, published in the journal Thyroid, examined iodine concentrations in kitchen salt and urine samples of schoolchildren and compared them to thyroid volume measurements. The findings raise concerns about a potential resurgence of iodine deficiency and underscore the importance of continuous monitoring of iodine status.
How Iodine Status Is Monitored
The WHO guide presents methods for monitoring iodine status and determining urinary iodine. It also provides procedures for monitoring salt iodine content at the factory, importation site, and household level. A guideline developed by WHO, UNICEF, and the International Council for Control of Iodine Deficiency Disorders, now the Iodine Global Network, frames these activities within programs for assessing deficiency and monitoring its elimination.
From Goiter to Salt Iodization
Iodine deficiency disorders include hypothyroidism, goiter, and adverse obstetric outcomes because inadequate iodine can limit thyroid hormone synthesis. Goiter was documented by physicians and naturalists across thousands of years and dozens of civilizations, with ancient healers in China, India, and Rome experimenting with seaweed and burned sea. Salt iodization, first used in Switzerland and the United States in the 1920s, became the mainstay of prevention efforts and was associated with a dramatic reduction in global iodine deficiency disorders over the following 30 years.
The Brazilian Iodine Study: Key Findings
Researchers from the University of Ribeirão Preto and the Faculty of Medicine of Ribeirão Preto USP conducted two studies, one in 2007 and another in 2015, involving schoolchildren aged 8-10 years from three schools representing different socioeconomic levels. They analyzed iodine levels in salt samples from the children's homes and in their urine, correlating these with thyroid volume assessed by palpation.
- Discrepancies in Salt Iodine (2007): Significant variation in iodine concentrations in salt samples.
- Adequate Urinary Iodine (2007): Most children had adequate urinary iodine levels, with a substantial portion exceeding the World Health Organization's (WHO) recommended limit.
- Shift in Salt Iodination Norms: A change in Brazilian regulations lowered the target range for salt iodination between the two studies.
- Lower Ioduria Levels (2015): A significant reduction in urinary iodine levels was observed in the 2015 study, with a concerning percentage of children showing levels below 100 µg/L, the WHO's cutoff for iodine deficiency.
- Increased Goiter Prevalence (2015): A higher proportion of children in the lowest socioeconomic school (School 1) exhibited goiter.
- Iodide Concentration (mg/kg) Findings: The iodine concentration in the industrialized salt samples for domestic consumption (mg/kg) were more uniform in 2015 and were within the range recommended by ANVISA. Iodine concentrations varied from 8.42 mg/kg at School 2 to 125 mg/kg at School 3 in 2007 and from 23.36 mg/kg at School 1 to 39.86 mg/kg at School 2 in 2015.
Signs of a Possible Reemergence
A 2024 review reports that iodine deficiency hypothyroidism is an important cause of neurocognitive and motor impairment in children globally. In the United States, universal salt iodization began in the 1920s and led to a dramatic decline in iodine deficiency hypothyroidism, but the review says deficiency may be reemerging alongside increased consumption of noniodized salts and decreased dairy iodine concentrations. A separate retrospective review at a tertiary pediatric endocrine clinic identified four children who met its diagnostic criteria for iodine deficiency, defined by a low urine iodine level.
Why Deficiency Still Matters
The reported consequences of iodine deficiency are substantial rather than limited to thyroid enlargement. One review identifies mental developmental problems in children, including lower IQ levels in school-aged children, and impaired maternal and fetal thyroid-hormone synthesis during pregnancy. WHO states that iodine-deficiency disorders can begin before birth and, during the neonatal period, childhood, and adolescence, can lead to hypothyroidism and hyperthyroidism.
Evidence Across Populations
The Cochrane review searched for studies comparing iodine supplementation with placebo in children and adolescents at risk of iodine deficiency and assessed confidence according to study methods and sample sizes. A pediatric review reports that iodine deficiency from the first months of life can significantly affect psychosomatic development, while prevention policies in many countries have improved dietary iodine status. In children with classical galactosaemia, iodine-fortified dairy-alternative milk was the leading dietary source, followed by fish or shellfish and eggs.
What Does This Mean for You?
The Brazilian study serves as a reminder that the fight against iodine deficiency is not over. Here are key takeaways: <b>Stay Informed:</b> Be aware of iodine recommendations, especially for children and pregnant women. The WHO recommends 120 µg of iodine daily for schoolchildren (7-12 years), 150 µg for adults, and 250 µg for pregnant and breastfeeding women. <b>Check Your Salt:</b> Ensure that your table salt is iodized. Look for the iodine symbol or check the label for potassium iodide or iodate. <b>Dietary Sources:</b> Include iodine-rich foods in your diet, such as seafood, dairy products, and eggs. <b>Consult Your Doctor:</b> If you have concerns about your iodine levels or thyroid health, talk to your healthcare provider. They can assess your iodine status and recommend appropriate interventions. By staying informed and proactive, you can help ensure that you and your family get enough iodine for optimal health and development.
Monitoring Remains Essential
Adequate iodine nutrition is essential for children's brain development and physical growth. The source on recent prevalence trends says vulnerable age groups remain at greater risk of iodine deficiency. It therefore argues for continuous monitoring of prevalence rather than assuming that earlier public-health gains have eliminated the problem.
Progress With Persistent Gaps
Nutritional deficiencies in iodine, vitamin A, and iron remain public-health challenges for children under 15 years, affecting growth, cognitive development, and long-term health outcomes. The cited epidemiological study reports that disparities persist across socioeconomic strata despite global interventions. Its projections indicate sustained declines in iodine and vitamin A deficiencies, while iron deficiency may stagnate, particularly in conflict-affected areas.
A Global and Unequal Burden
Nutritional deficiencies remain major public-health challenges for children under 15 years, and the cited research reports disparities across socioeconomic strata. Inadequate iodine intake affects populations in both developed and developing countries and is associated with goiter, hypothyroidism, impaired neurodevelopment, stillbirth, and infant mortality. A 2026 review adds that both iodine deficiency and iodine excess remain significant global challenges despite decades of progress in improving iodine supply.