Ingestion of infant formula constituted from fluoridated water associated with IQ deficit

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Till C, Green R, Flora D, Hornung R, Martinez-Mier EA, Blazer M, et al. Fluoride exposure from infant formula and child IQ in a Canadian birth cohort. Environ Int 2020;134:105315.

Question

Among otherwise normal preschool children, what is the association between fluoridated water used to constitute formula as infants/toddlers and IQ?

Design

Multicenter, prospective study drawn from participants in the Maternal-Infant Research on Environmental Chemicals (MIREC) program.

Setting

6 cities across Canada.

Participants

398 mother-child dyads, the children of which were 3-4 years old.

Intervention

Wechsler Primary and Preschool Scale of Intelligence-III.

Outcomes

IQ score.

Main Results

38% of the dyads lived in cities with fluoridated water. An increase of 0.5 mg/L in water fluoride concentration corresponded to a 9.3- and 6.2-point decrement in Performance IQ among both formula-fed (95% CI: −13.77 to −4.76) and breast-fed children (95% CI: −10.45 to −1.94), respectively.

Conclusions

Ingestion of formula constituted from fluoridated water is associated with Performance IQ deficits.

Commentary

This study by Till et al used data from the MIREC Study to demonstrate that fluoride intake from infant formula constituted from tap water is associated with lower performance IQ at age 3-4 years. Despite some limitations, eg, the use of estimated vs directly measured exposures to fluoride, the possibility of bias or confounding appears low. The results are consistent with increasing evidence suggesting that early life exposure to fluoride (prenatal and infancy) is associated with adverse neurobehavioral impacts. Evidence includes experimental studies in rodents as well as 3 recent longitudinal birth cohort studies (1 involving MIREC and 2 involving ourselves and colleagues) demonstrating significant associations between individual measures of prenatal fluoride exposure and lower performance on offspring measures of intelligence and behavior.

  • Green R.
  • Lanphear B.
  • Hornung R.
  • Flora D.
  • Martinez-Mier E.A.
  • Neufeld R.
  • et al.
Fluoride exposure during fetal development and intellectual abilities in a Canadian birth cohort.