Fluoride In Drinking Water Has No Effect On Iq Or Brain Function, Study Finds

• A new study finds no evidence that fluoridated drinking water affects children’s IQ or the cognitive abilities of older adults.
• Experts say fluoride in drinking water helps prevent tooth decay and cavities.
• They add that a person’s dental health directly affects their overall health.

Fluoride in drinking water does not affect children’s IQ or decrease cognitive abilities in older adults, according to a new, large-scale study.

The research, published on April 13 in the Proceedings of the National Academy of Sciences (PNAS), reports that there appears to be no difference at any stage of life between people who grow up with water fluoridation and those who do not.

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

The findings are in contrast to Health and Human Services (HHS) Secretary Robert F. Kennedy’s announcement in April that he would require the Centers for Disease Control and Prevention (CDC) to revise its long-standing recommendation that fluoride be added to drinking water.

They also contradict previous research, including a January study, that has suggested a possible link between fluoride and children’s IQ levels. Researchers noted that the studies were conducted in China and other countries with higher fluoride concentrations than permitted in the United States.

Scott Tomar, DMD, a spokesperson for the American Dental Association, said this research provides important information for the public at a critical time. Tomar wasn’t involved in the study.

“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 and associate dean for Prevention and Public Sciences at the College of Dentistry at the University of Illinois Chicago.

Danelle Fisher, MD, a pediatrician at Providence Saint John’s Health Center in Santa Monica, CA, said the findings confirm previous research on fluoridated water. Fisher wasn’t involved in the study.

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

No evidence to support negative impact of fluoride on cognition

The new 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 followed more than 10,000 people in that state since they graduated from high school in 1957. Participants took IQ tests at age 16, then had cognitive testing done at ages 53, 64, 72, and 80.

The original purpose of the Wisconsin study wasn’t focused on fluoride so there was no data available on urine or blood tests that would have measured exact levels of fluoride. Warren’s team based their estimates on exposure from records of when community water fluoridation began in certain areas.

The new findings follow a November 2025 study led by Warren that found no link between community water fluoridation in early life and brain function in people at age 60.

Experts note that fluoridation at appropriate levels doesn’t appear to cause any negative health effects.

“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 told Healthline.

Graham Tse, MD, a pediatrician and chief medical officer of MemorialCare Miller Children’s & Women’s Hospital in Long Beach, CA, agreed that the low levels of fluoride in U.S. drinking water pose no threat. Tse wasn’t involved in the study.

“There is no evidence of any health impacts,” Tse told Healthline.

He added that fluoride, like vitamins or other substances, can pose some issues if people are exposed to high levels. “That’s the case with many, many things,” Tse said.

Health benefits of fluoride in drinking water

The health benefits of fluoride in drinking water were first studied in 1909 in Colorado.

In 1945, Grand Rapids, Michigan, became the first state to add fluoride to its municipal water in an effort to help prevent tooth decay. Initial studies reported that tooth decay among Grand Rapids schoolchildren born after 1945 had declined by 60%.

In 1962, the U.S. Public Health Service recommended fluoridation in drinking water.

The CDC states that the optimal level of fluoride in drinking water to prevent cavities is 0.7 milligrams (mg) per liter (L). That amounts to 3 drops in a 55-gallon barrel. The legal limit for drinking water in the United States is 4 mg/L.

Today, more than 70% of people in the United States on public water systems receive fluoridated water. That represents more than 200 million Americans.

However, that number is shrinking. Two states — Utah and Florida — have enacted bans on fluoride in drinking water. Several other states, including Kentucky, Louisiana, Missouri, and Oklahoma, have pending legislation to limit fluoride.

In addition, 86 Wisconsin communities have stopped adding fluoride to municipal water systems since 1995.

Health organizations such as the American Dental Association and the American Academy of Pediatrics (AAP) support the fluoridization of drinking water.

Fluoride, a chemical found in nature as well as in toothpaste and drinking water, works by inhibiting the growth of bacteria that cause cavities, strengthening the hard outer enamel of teeth, reversing the damage caused by cavities, and supporting new bone formation.

Excessive fluoride intake, however, may cause fluorosis, a condition that can result in white spots or brown stains on teeth.

Experts say the benefits of fluoridated water are numerous and widespread.

“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.”

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

Health impacts of poor dental health

Your dental health can have a profound effect on your overall health.

Among other issues, gum disease can affect blood sugar levels in people with diabetes and increase the risk of heart disease and respiratory infections.

In addition, poor dental health can also lead to the development of diabetes and other chronic diseases later in life.

Poor dental health can also affect people with chronic kidney disease.

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

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

“Oral health isn’t limited to the mouth,” Tse noted. “It’s connected to overall health.”

Best ways to take care of your teeth

CDC officials say there are a number of ways you can promote good oral health. Among their suggestions:

• 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.

Fisher agreed with these recommendations and added a few more suggestions for parents.

She said adults should set a good example for children on regular brushing and flossing. She adds that parents should avoid giving children too many drinks and foods with added sugars.

Fisher said babies should never fall asleep while drinking juice or soda from a bottle. That allows sugar to coat their tiny teeth. She added that gummy products can also stick to teeth and should be used sparingly.

Tse agreed that good dental habits are important for children, as their teeth are still growing. He said that if everyone had access to quality dental care and adhered to healthy dental habits every day, then perhaps fluoridated water wouldn’t be necessary.

“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.”