A long-term US study shows water fluoridation at recommended levels doesn’t reduce cognitive ability, with kids who drank such water doing slightly better in school tests.
Whereas earlier studies looked at exposure to very high levels of fluoride, far beyond recommended standards, a new paper in Science Advances looks at more representative water fluoridation levels.
Researchers looked at language and maths test results from tens of thousands of US high schoolers in 1980, and the water fluoride levels they were exposed to since conception. After accounting for other factors, kids exposed to at least 0.7 mg/L of water fluoride had better results.
A follow up with a subset of participants until around age 60 showed that, although this cognitive edge became insignificant, growing up with recommended water fluoride levels didn’t contribute to cognitive decline.
Accompanying Focus article available here.
The Science Media Centre asked experts to comment.
Associate Professor Matthew Hobbs, Adjunct Researcher in the Faculty of Health, University of Canterbury, comments:
“This study provides important longer-term evidence that community water fluoridation is a safe and effective public health measure. By following more than 26,000 people from adolescence into later life, the researchers found no indication that recommended levels of fluoride in drinking water harm cognitive development or contribute to cognitive decline. These findings align with decades of high-quality international research showing that concerns about fluoride and cognition stem from studies of populations exposed to extremely high fluoride levels not from community water fluoridation.
“From a public health perspective, this matters. Community water fluoridation remains one of the most equitable and cost-effective ways to prevent tooth decay, particularly for children and for communities with limited access to dental care. This new evidence reinforces that we can continue to deliver these benefits without compromising cognitive health at any stage of life. It strengthens the case for maintaining fluoridation as a cornerstone of population-level oral health policy as outlined in the World Health Organisations Global Strategy and Action Plan on Oral Health 2023–2030. These findings reinforce the conclusions of the New Zealand Prime Minister’s Chief Science Advisor’s recent review, which found no credible evidence of neurodevelopmental harm at fluoridation levels used in Aotearoa.”
No conflicts of interest.
Dr Justin Wall (Te Rarawa, Te Aupōuri), tumuaki of Te Rōpū Niho Ora and practising dentist, comments:
“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 paper is entirely consistent with the information that has been gathered over many, many, many years of studying the fluoride supplementation of the domestic water supply.
“The principal thing that is always to be examined is whether or not there is any harmful effect of the fluoride supplementation. And this paper clearly demonstrates that there is no harm. Information around or research around the efficacy of fluoridation of the water supply is beyond doubt, and has been well and truly established for many, many years. And the concern the public will always have is that something that is applied to them, whether or not that is harmful, and this research clearly demonstrates that that is not the case. So, it’s a refreshing piece of research, and in particular because it has gone on for such a long period of time, and it has gone on in a country that is profoundly litigious. So, for this amount of research to be done over such a long period of time in America, I think it has to be taken seriously.
“I think that the research itself can be applied internationally. It’s not something that’s simply restricted to the environment in America. It is something that is well and truly applicable to New Zealand, and this research should go all the way to reassure the public of New Zealand and the municipal authorities who are being charged with implementing the fluoridation of the water supply that this is a safe and effective means of protecting the health of all New Zealanders.
“Furthermore, the health system, as we know, is under pressure, and any measure that can be taken to reduce the pressure on the health system, across the board, needs to be supported. And without a doubt that is the case with fluoridation.”
No conflicts of interest.
Professor Jonathan Broadbent, Professor of Dental Epidemiology and Public Health, University of Otago, comments:
“The US study addresses an important knowledge gap, as few studies have investigated this issue. It is reassuring that no association was found. This is consistent with findings from a recent Australian study and an older NZ study. However, some other studies have found associations between fluoride and cognitive issues, generally at higher concentrations than used in fluoridation programmes.
“There has been limited recent New Zealand research on community water fluoridation. With new fluoridation programmes being launched in New Zealand ongoing research is greatly needed; this is a necessary part of stewardship in running public health interventions such as fluoridation. New fluoridation programmes in NZ have been focused on areas with higher proportions of deprived New Zealanders and so should have good benefits for oral health, which tends to be worse in areas with greater deprivation. On the other hand, other health issues that occur at greater rates in deprived areas so spurious associations could be found. It is essential that the outcomes of these new programmes are monitored carefully.”
No conflicts of interest.