Iodine for Cognitive Function

Research suggests that iodine status plays a meaningful role in cognitive function, particularly during critical developmental windows such as pregnancy and early childhood, with multiple observational studies and reviews indicating that deficiency during these periods is associated with lower IQ scores, impaired memory, and reduced processing speed in children. A 2022 study in Portuguese schoolchildren found that moderately iodine-deficient children scored approximately 15 IQ points lower than their adequately nourished peers, and a 2025 review of maternal iodine intake concluded that the relationship between iodine and neurodevelopment follows a U-shaped pattern, meaning both deficiency and excessive intake may harm cognitive outcomes — a finding echoed by rat studies showing that very high iodine levels in pregnant mothers disrupted offspring brain development similarly to deficiency. The evidence is more mixed and less conclusive in adult and older populations: a 2023 Bangladeshi cohort study found modest associations between low iodine and reduced processing speed in children but noted that most participants had adequate intake, while a 2025 cross-sectional NHANES study unexpectedly found that iodine-deficient older adults showed lower risk of poor cognitive performance compared to those with adequate levels — a counterintuitive result the authors caution against over-interpreting given the study's inability to establish causation. Most of the available evidence comes from observational studies, cross-sectional analyses, and narrative reviews rather than controlled trials, and researchers have consistently noted that more rigorous clinical trials are needed to establish whether iodine supplementation during mild-to-moderate deficiency translates into measurable, long-term cognitive benefits.