Our IQ Will Start Dropping Soon (new evidence)

Goiter and Iodine Deficiency

• Goiter is an enlarged thyroid gland, often visible as swelling at the front of the neck.
• Early observations in animals and humans linked thyroid enlargement to what was later understood as insufficient iodine.

Key Medical Hypothesis and Human Experiment (1917–1922)

• David Marin (a pathologist) proposed that what was seen as a “poison” could be a cure for goiter by providing iodine.

Study design (as described)

• Target population: ~4,500 schoolgirls in Ohio (fifth grade and older)
• Intervention: sodium iodide dissolved in water, given in short courses every 6 months
• Grouping:
  • Girls with parental consent received iodine
  • Girls without parental response served as the control group
• Rationale for girls: goiter was reported as about twice as common in girls as in boys

Results

• Control (no iodine): >25% developed goiter
• Iodine group: goiter appeared in only 0.2%

Public Health “Supply Chain” Intervention: Iodized Salt

• David Murray Cowie linked goiter prevalence to geography (“goiter zone”), arguing that glaciers removed fertile soil—including iodine.
• Proposed/used mechanism: iodine is best delivered via a widely consumed, shelf-stable staple.

Intervention

• Add potassium iodide to table salt

Timeline and reported impact

• Since 1924, American table salt contained potassium iodide; goiter incidence fell sharply
• Similar outcomes were reported from Switzerland and Italy (associated with iodized salt and school curricula)
• Estimated global cost: 2–5 cents per person per year

“Accidental Iodine” Sources Declined

Even when iodized salt content dropped, population iodine status was partially protected by:

• Iodine in dairy: iodine-based antiseptics used in milking equipment contaminated milk with iodine
• Iodate in bread/flour: iodate used as a flour improver for machine processing

Decline drivers (as described)

• Dairy farmers switched away from iodine disinfectants
• Around 1980, bakers replaced iodate with bromate

Reported iodine decrease in the US

• Between the early 1970s and early 1990s, iodine levels dropped more than half (about 320 → 145)

Example outside the US

• In Australia, after dairy industry changes in the 1990s, iodine deficiency returned within 5 years

Iodine and Cognitive Performance

Randomized controlled trial (2009, Dunedin, New Zealand)

• Participants: 184 schoolchildren
• Outcome: the iodine group showed ~0.19 standard deviations higher overall cognitive performance, including improved perceptual thinking

Natural-Experiment Evidence Linking Iodine to IQ

• Economists analyzed US military draft records (2013 study)

Logic

• Iodized salt introduced in 1924
• Those born after iodization were tested about 18 years later (pre-WWII draft testing), while earlier cohorts had more deficiency exposure

Reported finding

• Males born after iodized salt introduction scored ~1 standard deviation higher (about 15 IQ points) than earlier cohorts

Caveat noted in the video: not a randomized controlled trial, but consistent with other evidence.

Summarized literature estimate

• Moderate–severe childhood iodine deficiency linked to ~12–13.5 IQ point reduction

Current Risk: Iodine Deficiency Resurgence and Weakened Pillars

• WHO framing: iodine deficiency is the most common preventable cause of intellectual disability worldwide.

Reported US trend (iodine levels)

• Adults (2001–2020): 153 → 116
• Children: 243 → 166

Interpretation (in the video)

• Not yet severely deficient, but iodine supply has eroded and may fall further.

Reasons given

• Reduced coverage of iodized salt (described as voluntary, not mandated)
• Loss of incidental iodine from dairy and bread
• Non-iodized “trendy” salts (sea salt, kosher salt, pink Himalayan salt)
• Many processed foods use non-iodized salt

Diet-based insufficiency claim

• Fish/eggs may not provide enough iodine compared with requirements
  • Example: canned tuna ~7 micrograms vs daily need ~150 micrograms
• Many plant foods are listed as low in iodine (~1–3 micrograms)

Pregnancy and Iodine Needs

• The video claims pregnancy increases iodine requirement by ~50% during brain development.
• It also links low maternal iodine status to risk of childhood neurodevelopment issues.

Testing Limitations and Clinical Recommendation

Testing limitations (as stated)

• Urine testing: reflects population levels but is not ideal for individual “dynamic” changes
• TSH: can appear normal even with low iodine intake

Recommendations described

• Pregnant women: iodine supplement 150 micrograms + folate (per clinical guidelines cited in the video)
• Adults/children: generally avoid high-dose iodine unless there is a medical indication

Supplement Quality Control

• Suggestion: check iodine supplements for accurate testing and labeling via ConsumerLab.com or Labdoor.com, citing inconsistencies between label claims and measured content.

Salt Substitutes and Blood Pressure/Stroke

• Evidence referenced (as stated in the video):
  • Salt reduction lowers blood pressure (meta-analysis across 85 studies)
  • Salt substitute trial: 14% reduced stroke risk over 4.74 years

Researchers / Sources Featured (as explicitly named)

• David Marin
• O. P. Kimball
• O. J. Kimball (co-mentioned with O.P. Kimball in the experiment)
• David Murray Cowie
• World Health Organization (WHO)
• Economists (2013 study) — not individually named in the subtitles
• Randomized controlled trial investigators (2009 Dunedin, NZ) — not individually named in the subtitles
• ConsumerLab.com
• Labdoor.com