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.
Evidence
Categorization
- corroborated: 2 independent passages support this claim
- XREF: connects to: Iodizing salt in 1924 closed a 15-point IQ gap cheaply; 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. — Cretinism - an overview; 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. — Timing of Vulnerability of the Brain to Iodine Deficiency in Endemic Cretinism (+20 more)
Related
- 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 0.95)
- We find that for the one quarter of the population most deficient in iodine this intervention raised IQ by approximately one standard deviation. (similarity 0.93)
- 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 0.92)
- 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. (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 0.91)
- 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 0.91)
- 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 0.90)
- 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 0.90)
- 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 0.90)
- 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 0.90)
- Introduction of iodized salt increased IQ by approximately 15 points for those most deficient in iodine. (similarity 0.88)
- Iodine played a substantial role in cognitive improvements across the American population in the 20th century. (similarity 0.88)
- Iodine deficiency is the leading global cause of mental retardation (similarity 0.88)
- A 2013 study found a gradual increase in average intelligence of 1 standard deviation, 15 points in iodine-deficient areas and 3.5 points nationally after the introduction of iodised salt. (similarity 0.88)
- 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 0.87)
Library Connections
- Adding iodine to salt in 1924 raised average U.S. IQ scores
#corroborates(0.90) — Did iodized salt raise the IQ of 50 million Americans by 15 points? - Iodine deficiency is a major unrecognized cause of lowered intelligence
#corroborates(0.85) — Harriet A. Washington, A Terrible Thing to Waste, 21 - Adding iodine to salt closed a 15-point IQ gap cheaply
#corroborates(0.85) — Harriet A. Washington, A Terrible Thing to Waste, 18