Largest US Study Links Fluoride to Cognitive Benefits

A groundbreaking study conducted by the University of Minnesota has revealed new insights into the effects of fluoride in drinking water on brain function. This research, the largest of its kind in the United States, indicates that fluoride at recommended levels does not negatively impact cognition and may actually enhance cognitive outcomes.

Over a span of more than 40 years, the study analyzed data from 26,820 individuals selected from the 1980 High School and Beyond cohort, which initially surveyed 58,270 students across 1,020 American high schools. Participants were reinterviewed multiple times until 2021, allowing researchers to assess the long-term effects of fluoride exposure on cognitive abilities.

To investigate this relationship, the researchers matched academic performance data with the fluoridation status of the participants’ communities. This information was sourced from the US Department of Health and Human Services’ Fluoridation Census, covering the years from 1967 to 1993. Additionally, they utilized data from the US Geological Survey, measuring fluoride levels in untreated groundwater from 38,105 wells between 1988 and 2017.

The findings suggest that children exposed to fluoride levels between 0.7 and 1.2 mg/liter (prior to 2015) and 0.7 mg/L thereafter had significantly higher scores in vocabulary, reading, and mathematics by the end of their schooling. Although these advantages appeared to persist into middle age, the researchers noted that the results were not statistically significant.

“This is a great example of understanding the data and scientific research used to draw conclusions,” stated Gina Rumore, a study author at the Life Course Center. She emphasized that while excessive fluoride can be toxic, levels recommended for drinking water have been shown to be safe and beneficial. “Fluoridating drinking water is known to have massive oral health benefits, and now it appears that it also leads to better – not worse – cognitive test performance.”

Debate over fluoride in drinking water has been contentious for decades. Earlier this year, the US Health and Human Services proposed removing fluoride from local supplies, with states like Utah and Florida already eliminating it entirely. A 2024 investigation revealed that there are ten states where less than half of residents with access to public water supplies receive fluoridated water.

Historically, fluoride was first introduced in Grand Rapids, Michigan, in January 1945, based on evidence indicating that fluoride could significantly reduce tooth decay. Despite its proven dental benefits, the initiative faced considerable backlash, and misinformation has been perpetuated through smaller studies conducted in countries like China, India, and Iran, where populations were exposed to fluoride levels far exceeding those in the United States.

In light of this, John Robert Warren, another study author, emphasized the need for public awareness. “There is absolutely no credible scientific evidence to support the claim that putting fluoride in municipal drinking water at recommended levels harms children’s IQ. In fact, the opposite appears to be true,” he stated.

The researchers conducted supplementary analyses, accounting for various factors, including students’ community environments. Their findings remained consistent regardless of whether participants lived in fluoridated or non-fluoridated areas. They also acknowledged limitations in their study, noting that more comprehensive data on participants’ fluoride exposure during their formative years would have strengthened their conclusions.

Despite these constraints, the researchers assert that their results provide compelling evidence that fluoride exposure at levels typically found in the United States is beneficial for adolescent cognition and does not adversely affect cognitive functioning later in life.

Fluoride toxicity can lead to conditions such as fluorosis, resulting in tooth discoloration and potential bone deterioration. However, the majority of scientific data on fluorosis has been collected from regions with significantly higher natural fluoride levels than those recommended by the Centers for Disease Control and Prevention (CDC), which advises a concentration of 0.7 mg/L in drinking water.

While the study does not definitively prove that fluoride-treated water enhances brain function, it establishes a correlation. Importantly, no relationship was found between fluoride exposure and the prevalence of neurodevelopmental disorders among children and adolescents.

“This study provides important longer-term evidence that community water fluoridation is a safe and effective public health measure,” remarked Matthew Hobbs from the University of Canterbury in New Zealand. He noted that concerns regarding fluoride and cognitive effects often stem from studies of populations exposed to extremely high fluoride levels rather than from community water fluoridation.

The dental health benefits of fluoride have been substantiated over decades of research. Justin Wall from Te Rōpū Niho Ora (Oral Health New Zealand) highlighted the significance of this research, particularly its extended duration and its context within a litigious country. “This research demonstrates that fluoridation is safe for all ages,” he stated, underscoring the importance of preserving dental health in an aging population.

The findings from this comprehensive study were published in the journal Science Advances, further contributing to the ongoing discourse around fluoride in public health.