Iodine deficiency results in a global loss of 10-15 IQ points at a population level and is the world’s greatest single cause of preventable brain damage.

Evidence

Cretinism - an overview (ScienceDirect)

Categorization

• corroborated: 2 independent passages support this claim
• XREF: connects to: Iodizing salt in 1924 closed a 15-point IQ gap cheaply; For the quarter of the population most deficient in iodine, salt iodization raised IQ by approximately one standard deviation, explaining roughly a decade’s worth of the Flynn Effect. — The Cognitive Effects of Micronutrient Deficiency: Evidence from Salt Iodization in the United States; Iodine deficiency is the leading global cause of mental retardation — The Cognitive Effects of Micronutrient Deficiency: Evidence from Salt Iodization in the United States (+15 more)

Related

• For the quarter of the population most deficient in iodine, salt iodization raised IQ by approximately one standard deviation, explaining roughly a decade’s worth of the Flynn Effect. (similarity 0.92)
• In populations with severe endemic iodine deficiency, mild mental impairment occurs five times as frequently as cretinism, shifting the population IQ curve 10 points to the left. (similarity 0.92)
• Iodine deficiency impairs brain development in children even without obvious physical effects like goiter, and even relatively low fetal deficiency can significantly reduce IQ. (similarity 0.91)
• Iodine deficiency is the leading global cause of mental retardation (similarity 0.91)
• A randomized trial in Ethiopia found iodized salt raised children’s cognitive scores by only about 4 IQ points (effect size d=0.17), far below a full standard deviation. (similarity 0.87)
• The lower range of estimates is consistent with iodization raising IQ by 15 points, but also documents at least 10,000 excess deaths from iodine-induced hyperthyroidism. (similarity 0.86)
• Iodine played a substantial role in cognitive improvements across the American population in the 20th century. (similarity 0.86)
• Iodized salt raised IQs by a full standard deviation (15 points) in iodine-deficient areas, and may explain a decade’s worth of the Flynn effect. (similarity 0.86)
• A 2017 study found that the introduction of iodized salt in 1924 raised IQ for the one-quarter of the population most deficient in iodine. (similarity 0.86)
• We find that for the one quarter of the population most deficient in iodine this intervention raised IQ by approximately one standard deviation. (similarity 0.85)
• Results are consistent with iodization raising IQ by 15 points in iodine-deficient areas and a nationwide average increase of ~3.5 IQ points. (similarity 0.85)
• Salt iodization beginning in 1924 raised IQ by approximately one standard deviation (15 points) for the quarter of the population most deficient in iodine. (similarity 0.85)
• Iodine deficiency is a major unrecognized cause of lowered intelligence (similarity 0.84)
• Introduction of iodized salt increased IQ by approximately 15 points for those most deficient in iodine. (similarity 0.84)
• Salt iodization raised IQ scores of millions of people by 15 IQ points in iodine-deficient regions and is highly cost-effective at pennies per person per year. (similarity 0.84)

Library Connections

• Iodine deficiency is the leading global cause of mental retardation #corroborates (0.95) — The Cognitive Effects of Micronutrient Deficiency: Evidence from Salt Iodization in the United States
• Iodine deficiency is a major unrecognized cause of lowered intelligence #corroborates (0.90) — Harriet A. Washington, A Terrible Thing to Waste, 21
• Adding iodine to salt closed a 15-point IQ gap cheaply #exemplifies (0.90) — Harriet A. Washington, A Terrible Thing to Waste, 18
• Adding iodine to salt in 1924 raised average U.S. IQ scores #exemplifies (0.85) — Did iodized salt raise the IQ of 50 million Americans by 15 points?