In the first American study dedicated to the impact of recommended fluoride levels in drinking water on brain function, scientists concluded that this mineral does not have a negative effect on cognitive abilities. In fact, it may even help improve them.

Large-Scale Study on the Effects of Fluoride

A research team from the University of Minnesota analyzed the relationship between fluoride content in drinking water and cognitive performance in people from childhood to middle age. The study spanned over 40 years and became the first of its kind in the U.S. in terms of scale and duration. Out of 58,270 high school students surveyed in 1,020 American schools in 1980, a random subgroup of 26,820 people was selected and followed up with until 2021.

The researchers compared participants’ academic achievements with their place of residence and the fluoridation status of water in those regions, using data from the U.S. Department of Health (1967–1993) and the U.S. Geological Survey on fluoride content in groundwater (38,105 wells, 1988–2017). They also took into account changes in fluoridation recommendations, which in 2015 nearly halved the recommended levels.

Results and Conclusions

Children who received the recommended levels of fluoride in drinking water (0.7–1.2 mg/L from 1962 to 2015 and 0.7 mg/L since 2015) generally showed higher academic performance in all subjects by the end of school, especially in vocabulary, reading, and mathematics. This advantage persisted for some participants up to age 60, although these results did not reach statistical significance.

Gina Rumor from the Life Course Center noted: “While extremely high levels of fluoride can be toxic, fluoride in drinking water at recommended levels is not. Water fluoridation is well known for its benefits to oral health, and now it is also linked to better cognitive outcomes.”

Debates Around Fluoridation

Fluoride in drinking water has been a topic of debate for decades. In early 2024, the U.S. Department of Health proposed removing it from municipal water systems. In some states, such as Utah and Florida, fluoride has been completely eliminated, and in ten other states, less than half of residents using public water supplies receive fluoridated water.

The reasons for these disagreements are complex. Fluoride was first added to water in 1945 in Grand Rapids, Michigan, after evidence of its effectiveness in reducing cavities. However, the idea of “forced medication” sparked resistance and became one of the most discussed topics in dentistry. Several small studies in China, India, and Iran, where children were exposed to high levels of fluoride, fueled misinformation campaigns, even though fluoride levels there were much higher than in the U.S. One study linking fluoride to low IQ was later debunked.

Study co-author John Robert Warren emphasized: “There is no reliable scientific evidence that adding fluoride to drinking water at recommended levels harms children’s intelligence. In fact, the opposite is true.”

Additional Analyses and Limitations

The researchers conducted further analyses to account for variables such as students living in different communities with fluoridated or non-fluoridated water. The analysis showed the same pattern as in the main group. They also attempted to separate the biological effects of fluoride from social, cultural, economic, and political factors that could influence decisions about water fluoridation.

The scientists also noted some limitations of the study. First, they could not obtain complete information about participants’ places of residence from conception to late adolescence, so they used data on where they attended high school. Second, there was no precise data on actual fluoride consumption; instead, the chemical composition of the water was analyzed. Third, there was insufficient data on lifelong fluoride exposure to assess its impact on adult cognitive function.

Nevertheless, the study’s results convincingly show that exposure to fluoride at levels commonly found in the U.S. is beneficial for adolescents’ cognitive abilities and, at the very least, not harmful for adults.

Safety and Effectiveness of Fluoridation

Fluoride toxicity can lead to fluorosis, which causes tooth discoloration and bone damage, but such cases are mainly recorded in regions with naturally high fluoride content, significantly exceeding the CDC’s U.S. recommendations (0.7 mg/L). For example, in India’s groundwater, the average fluoride content is 2.37 mg/L, and in some areas, it reaches up to 9.22 mg/L.

Although the study does not prove that fluoridated water improves brain function, a positive correlation was found. Importantly, no link was found between fluoride and the prevalence of neurodevelopmental disorders in children and adolescents.

Associate Professor Matthew Hobbs from the University of Canterbury (New Zealand) commented: “This study provides important long-term evidence that community water fluoridation is a safe and effective public health measure. These findings are consistent with decades of international research showing that concerns about fluoride and cognitive function are based on studies of populations exposed to extremely high fluoride levels, not on data from community water fluoridation.”

Justin Wall from Te Rōpū Niho Ora (New Zealand Dental Health) added: “This study shows that fluoridation is safe for all ages, and as the number of elderly people retaining their teeth grows, we need to protect their oral health as they age.”

Conclusion

The benefits of fluoride for dental health have been confirmed by decades of research. The new large-scale study conducted in the U.S. deserves serious attention, as it confirms the safety and potential cognitive benefits of water fluoridation for the population.

The study was published in the journal Science Advances.