Does Fluoride In Drinking Water Impact Brain Power? A Huge 40-Year Study Weighs In

A massive 40-year study in the US has concluded that adding fluoride to drinking water does not reduce people's cognitive ability. In fact, kids who grew up with fluoridated tap water performed slightly better in mathematics and reading in later life compared to those who didn’t.

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Scientists at the University of Minnesota looked at data from reading comprehension, mathematics, and vocabulary tests given to around 26,820 people in over 1,000 American high schools between 1980 and 2021. This was paired with information about the fluoride levels they would've experienced since conception, plus other data about their wider health, socioeconomic background, environment, and other factors. 

The bottom line: the study found drinking water with the recommended level of fluoride (0.7 milligrams per liter) had no negative impact on people's brain power in their teenage years or their adult life.

If anything, people who drank fluoridated tap water had “modestly” better test results, although the research did not unravel why this might be the case. 

Fluoride is a naturally occurring mineral that’s added to public water supplies in certain parts of the world to reduce tooth decay. Also found in most toothpastes, it works by strengthening tooth enamel, making it more resistant to acid attacks from bacteria in the mouth, and helping to repair early stages of tooth decay before cavities form.

Some people oppose the idea of adding this chemical to the water supply, especially in the US where it's become a divisive, politically charged topic over recent decades.

Recently, the debate has been reignited by Robert F. Kennedy Jr., the chief of the US Department of Health and Human Services, who has called fluoride “industrial waste” and urged states to ban it in drinking water.

Opponents often cite potential health risks, and object to mandatory public health measures on the grounds of individuals' rights. One recurring concern is whether fluoride affects children’s IQ. While a recent meta-analysis reported a slight decrease in IQ with higher fluoride exposure, many experts poo-pooed the paper, arguing that it contained biased data and didn’t show the whole picture. 

This new long-term study adds weight to the heated discussion. It may not convince the un-convincible, but it builds on the growing body of evidence that fluoride is safe when used at recommended levels.

"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,” Associate Professor Matthew Hobbs, Adjunct Researcher in the Faculty of Health at the University of Canterbury, who was not involved in study, said in a statement.

“This new evidence reinforces that we can continue to deliver these benefits without compromising cognitive health at any stage of life,” Hobbs added.

The study is published in the journal Science Advances.