New Study Finds No Link Between Fluoride in Drinking Water and Brain Health

A major new study shows that fluoride in drinking water does not lower children’s IQ or harm the thinking skills of older adults.

The research, published April 13 in the journal Proceedings of the National Academy of Sciences (PNAS), found no difference in brain function at any age between people who grew up with fluoridated water and those who did not.

“We find no evidence that [community water fluoridation] is negatively associated with adolescent IQ or adult cognitive functioning,” the study authors wrote.

These findings go against a recent announcement from Health and Human Services (HHS) Secretary Robert F. Kennedy. In April, he said he would ask the Centers for Disease Control and Prevention (CDC) to change its long-standing recommendation to add fluoride to drinking water.

The new study also contradicts earlier research, including a January study that suggested a possible link between fluoride and children’s IQ. However, researchers noted that those studies were done in China and other countries where fluoride levels in water are much higher than what is allowed in the United States.

Scott Tomar, DMD, a spokesperson for the American Dental Association, said the study provides important facts at a key time. Tomar was not involved in the research.

“Despite misinformation that is out there, the best available evidence indicates that community water fluoridation has no effect on IQ, cognition, or other measures of neurodevelopment,” said Tomar, who is also a professor at the University of Illinois Chicago College of Dentistry.

Dr. Danelle Fisher, a pediatrician at Providence Saint John’s Health Center in Santa Monica, CA, said the results back up earlier studies on fluoridated water. Fisher was not part of the research team.

“They reassure us that the use of fluoride in proper amounts does not have any definitive effects on IQ,” she said. “It makes a good case for having fluoride in our drinking water.”

Study used decades of data from thousands of people

The study was led by Rob Warren, PhD, a sociologist and population health expert at the University of Minnesota. Warren used data from the Wisconsin Longitudinal Study, which has tracked more than 10,000 people since they graduated high school in 1957. Participants took IQ tests at age 16 and then had cognitive testing at ages 53, 64, 72, and 80.

The original Wisconsin study was not designed to look at fluoride, so there were no urine or blood tests to measure exact fluoride levels. Instead, Warren’s team estimated exposure by looking at records of when communities started adding fluoride to their water.

This new research follows a November 2025 study, also led by Warren, that found no link between early-life water fluoridation and brain function in people at age 60.

Experts say that when fluoride is used at proper levels, it does not appear to cause health problems.

“At the levels of fluoride that we use for community water fluoridation in the United States and other countries, there are no adverse health effects,” Tomar said.

Dr. Graham Tse, a pediatrician and chief medical officer at MemorialCare Miller Children’s & Women’s Hospital in Long Beach, CA, agreed. Tse was not involved in the study.

“There is no evidence of any health impacts,” he said. He added that, like many substances, fluoride can cause issues if people are exposed to very high amounts.

Why fluoride is added to drinking water

The health benefits of fluoride in water were first studied in 1909 in Colorado. In 1945, Grand Rapids, Michigan, became the first city to add fluoride to its water to prevent tooth decay. Early studies found that tooth decay in Grand Rapids schoolchildren born after 1945 dropped by 60%.

In 1962, the U.S. Public Health Service recommended adding fluoride to drinking water. The CDC says the best level for preventing cavities is 0.7 milligrams per liter. That is about 3 drops in a 55-gallon barrel. The legal limit in the United States is 4 mg per liter.

Today, more than 70% of people on public water systems in the U.S. receive fluoridated water. That is over 200 million Americans.

But that number is shrinking. Utah and Florida have banned fluoride in drinking water. Several other states, including Kentucky, Louisiana, Missouri, and Oklahoma, have proposed laws to limit fluoride. Also, 86 Wisconsin communities have stopped adding fluoride to their water since 1995.

Health groups such as the American Dental Association and the American Academy of Pediatrics support water fluoridation.

Fluoride is a natural chemical also found in toothpaste. It works by stopping bacteria that cause cavities, strengthening tooth enamel, reversing early cavity damage, and helping new bone growth. Too much fluoride can cause fluorosis, a condition that leaves white spots or brown stains on teeth.

Experts say the benefits of fluoridated water are clear.

“We have extremely consistent evidence that water fluoridation helps to prevent tooth decay and reduces its severity,” said Tomar. “We also have very consistent evidence that community water fluoridation saves money for families, communities, and state governments by reducing dental costs and missed days of work or school due to dental problems.”

He added: “The primary danger of stopping fluoridation is that the levels of tooth decay, and its related treatment costs will increase. The effects show up first – and most pronounced – among the youngest children in the community but ultimately affects everyone.”

How poor dental health affects the whole body

Your dental health can have a major effect on your overall health. Gum disease can raise blood sugar in people with diabetes and increase the risk of heart disease and respiratory infections. Poor dental health can also lead to diabetes and other chronic diseases later in life. It can also harm people with chronic kidney disease.

Dr. Fisher said cavities can lead to abscesses and infections that affect any part of the body.

“Cavities aren’t just little holes in your teeth,” she said. “Infections can spread and cause a wide variety of problems.”

Dr. Tse agreed: “Oral health isn’t limited to the mouth. It’s connected to overall health.”

Tips for good dental health

The CDC recommends several ways to keep your teeth healthy:

– Avoid foods and drinks with added sugars.

– Drink fluoridated water and use fluoridated toothpaste.

– Brush your teeth at least twice a day and floss regularly.

– Visit the dentist at least once a year.

Dr. Fisher said parents should set a good example by brushing and flossing regularly. She also advised limiting sugary drinks and foods for children. Babies should never fall asleep with a bottle of juice or soda, as the sugar coats their teeth. Gummy snacks can also stick to teeth and should be given sparingly.

Dr. Tse said good dental habits are especially important for children because their teeth are still growing. He noted that if everyone had access to quality dental care and practiced good habits daily, fluoridated water might not be needed.

“Maybe we wouldn’t need fluoridated drinking water under those circumstances, but that’s not the reality,” he said. “Fluoridation is a cheap, effective way to promote good dental care.”