Largest US Study Links Fluoride to Improved Cognitive Functions

In a groundbreaking study conducted by researchers at the University of Minnesota, findings reveal that fluoride levels in drinking water do not negatively impact cognitive function and may, in fact, enhance it. This research, the largest of its kind in the United States, examined the effects of fluoride exposure on cognitive outcomes over a span exceeding 40 years, marking a significant contribution to the ongoing debate about water fluoridation.

Study Overview and Methodology

Researchers analyzed data from a subset of 26,820 individuals drawn from the 1980 High School and Beyond cohort study, which originally involved 58,270 high school sophomores and seniors surveyed across 1,020 American high schools. Participants were reinterviewed multiple times through 2021, allowing for a comprehensive assessment of cognitive performance from childhood into middle age.

The study matched participants’ academic data with their locations and the fluoridation status of those areas, utilizing information from the US Department of Health and Human Services Fluoridation Census, covering the years 1967 to 1993. Additionally, data from the US Geological Survey provided insights into fluoride levels in untreated groundwater from 38,105 wells between 1988 and 2017.

Researchers focused on the fluoridation levels of 0.7 mg/liter and 1.2 mg/liter from 1962 to 2015, and the current 0.7 mg/L since 2015. They noted that children exposed to these levels demonstrated higher average scores in vocabulary, reading, and math by their final school year, with these advantages persisting into later life.

Findings and Implications

Despite the positive correlation observed, the study acknowledged that the results were not statistically significant. Gina Rumore, one of the study’s authors at the Life Course Center, remarked, “This is a great example of understanding the data and scientific research used to draw conclusions.” She emphasized that while extremely high fluoride levels can be toxic, fluoride at recommended levels does not negatively affect cognitive development.

The contentious nature of fluoride in drinking water has been a subject of debate for decades. Earlier this year, the US Health and Human Services suggested removing fluoride from local government supplies. States like Utah and Florida have already eliminated fluoride, while a 2024 report from US News & World Report revealed that there are ten additional states where less than half of residents have access to fluoridated public water supplies.

The history of fluoride use dates back to January 1945, when it was first introduced in Grand Rapids, Michigan. Initial evidence suggested that fluoride could significantly reduce tooth decay. However, the introduction of what some termed “compulsory medication” met with substantial opposition, further fueled by non-representative studies from countries like China, India, and Iran, where populations were exposed to fluoride levels far exceeding those in the US.

Critically, studies linking fluoride to lower IQ levels have been discredited over time. John Robert Warren, another author of the study, stated, “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.”

Limitations and Future Research

The researchers conducted additional analyses to account for variables such as community differences regarding fluoride exposure. They found that the cognitive benefits remained consistent among students who lived in the same community throughout their education as well as those who moved. This suggests that the correlation between fluoride and cognitive performance is robust across various living situations.

Despite the findings, the study does have limitations. Researchers expressed a desire for more comprehensive data on participants’ residency from conception through late adolescence. They also noted that while they could examine the water chemistry, they lacked specific information on individual fluoride consumption levels.

Importantly, the study did not establish that fluoride-treated water improves brain function, but it did find evidence of a correlation without links to neurodevelopmental conditions in children and adolescents. Matthew Hobbs, an Associate Professor from the University of Canterbury in New Zealand, commented, “This study provides important longer-term evidence that community water fluoridation is a safe and effective public health measure.”

Hobbs added that the findings align with decades of international research showing that concerns about fluoride and cognition stem from studies involving populations exposed to high fluoride levels, not from community water fluoridation.

As the dental health benefits of fluoride remain well-documented, this study serves as a crucial reminder of the public health implications of water fluoridation. Justin Wall, from Te Rōpū Niho Ora in New Zealand, noted, “This research demonstrates that fluoridation is safe for all ages, and with the growing older population who have retained their teeth, we need to protect their dentition as they age.”

The findings, published in the journal Science Advances, contribute significantly to the discourse surrounding fluoride use in public health policy, reinforcing its benefits while addressing longstanding concerns. As the debate continues, this research underscores the importance of informed decision-making based on credible scientific evidence.