A comprehensive study analyzing data from over 10,000 individuals has found no evidence that adding low levels of fluoride to community drinking water impacts children's IQ or long-term brain function. The research, which followed participants from their teen years into old age, examined longitudinal data from 10,317 high school seniors from 1957 to 2021.
Most health authorities endorse fluoridation at levels typical in U.S. community water, citing its proven benefits for dental health, strengthening teeth, and reducing decay. This new study found no association between community water fluoridation exposure and IQ or other measures of cognitive function later in life.
Concerns about fluoride's impact on IQ have been fueled by misinterpreted studies, particularly those focusing on high doses well above the recommended 0.7 mg/L by the U.S. Public Health Service. These often-cited studies, primarily from China and India, did not control for water contaminants and are not relevant to U.S. public policy debates regarding typical fluoridation levels.
Lead researcher John Robert Warren, a sociologist and demographer from the University of Minnesota, stated that decisions by some municipalities to remove fluoride from drinking water are based on flawed studies of massive doses. This new research, drawing on data from the Wisconsin Longitudinal Study, utilized historical fluoride content in water supplies and paired it with IQ scores of graduating students in 1957 to approximate exposure.
Participants were tested on cognitive abilities at ages 53, 64, 72, and 80, providing nearly 70 years of data. After adjusting for all available confounders, the study found no evidence of impaired cognitive performance in individuals exposed to fluoride through community water programs. Co-author Gina Rumore confirmed the results "provide no support for the claim that community water fluoridation has any harmful effect on children's IQ or on adult cognition."
The findings align with previous research by Warren and Rumore, which also found no significant association with water fluoridation. In fact, some studies suggest that poor dental health, which water fluoridation helps prevent, is linked to cognitive decline.