A new study commissioned by the National Institute of Environmental Health Sciences looked at the effect that high fluoride consumption can have on children’s IQ scores.
Recently published in JAMA Pediatrics, the study found that children who had the highest levels of fluoride exposure were also more likely to have lower IQs than those who had less fluoride exposure.
A look at the study
To better understand the relationship between fluoride and IQ, the researchers analyzed data from over 70 studies that explored this theme. They looked at fluoride consumed from drinking water, dental fluorosis, and other forms of fluoride consumption. All of the studies selected were conducted internationally, with over 60% being China-based studies.
Ultimately, the majority of studies involved in the analysis – 64 of the 74 selected – showed an inverse relationship between fluoride exposure and intelligence.
- This means that as fluoride exposure increased, overall IQ decreased, and vice versa.
A further look at the results
Another component of the researcher’s analysis was the risk of bias of each individual study. Using criteria from the National Toxicology Program’s or Division of Translational Toxicology’s OHAT approach, they were able to determine the level of bias in each study.
The team found that 52 studies involved in the report had a high level risk of bias, while the remaining 22 studies had a low risk of bias.
Ultimately, the researchers didn’t exclude any of the studies from their overall analysis. However, they did look specifically at the 22 studies with the low risk of bias to see if their initial findings held up.
When looking at just those studies, the outcome was the same – higher fluoride consumption was associated with lower IQ.
The researchers explained that many international countries have higher levels of fluoride in their drinking water than the United States. There also haven't been any U.S.-based studies looking at fluoride exposure and intelligence scores, which also makes it difficult to apply these results to the U.S. population.
“Elevated naturally occurring fluoride levels in groundwater are prevalent globally and include central Australia, eastern Brazil, sub-Saharan Africa, the southern Arabian Peninsula, south and east Asia, and western North America,” the researchers wrote.
“Although to our knowledge no epidemiological studies addressing fluoride exposure and children’s IQ have been conducted in the United States, significant inequalities in community water systems’ fluoride levels exist by county sociodemographic characteristics, including racial and ethnic composition, especially among Hispanic and Latino communities.”
While there are currently no recommendations on fluoride levels in drinking water based on developmental outcomes, the United States does recommend that all community water systems keep fluoride concentration at 0.7 mg/L.