Study Finds No Evidence Fluoride in Drinking Water Causes Cognitive Delays

New research published on April 13, 2026, indicates that community water fluoridation in the United States does not lead to a reduction in IQ or impaired brain function. The findings challenge recent claims that fluoride in tap water may cause cognitive delays in children, a concern that has influenced public health policy and legislative actions in several U.S. States.

The study, published in the Proceedings of the National Academy of Sciences, is the first of its kind to measure community water fluoridation exposure during childhood within the U.S. And track potential impacts on cognition up to age 80.

Study Findings and Cognitive Impact

According to the research, tests of intelligence and brain function showed consistent results regardless of whether the participants had consumed fluoridated water during their development. These results contradict assertions made by U.S. Secretary of Health and Human Services Robert F. Kennedy, Jr., who has claimed that fluoride is industrial waste associated with a loss of IQ.

Dr. Scott Tomar, head of the department of population oral health at the University of Illinois in Chicago, described the research as quite significant and stated that there is no association with community water fluoridation and any measure of IQ or neurodevelopment.

A separate decades-long study published in Science Advances on November 19, 2025, similarly found no evidence that exposure to recommended levels of fluoride lowers the cognitive skills of children. John Robert Warren, a sociologist at the University of Minnesota and co-author of that study, stated that the findings provide U.S.-based evidence that the public health intervention is safe.

Public Health Context and Policy Shifts

The debate over water fluoridation has led to significant policy changes across the United States. Concerns regarding brain development have prompted several cities and states to reevaluate or remove fluoride from their water supplies. Specifically, the states of Florida and Utah have enacted bans on the practice.

Additional legislation is currently pending in several other states, including Louisiana, Missouri, Oklahoma, and Kentucky.

The Centers for Disease Control and Prevention identifies the optimal level of fluoride in drinking water to prevent cavities as 0.7 milligrams per liter.

Evaluating Previous Research

Opponents of water fluoridation have frequently cited smaller studies suggesting a link between fluoride and lower IQ scores in children. However, the April 13, 2026, report notes that those studies were conducted in other countries, such as China, where fluoride concentrations were significantly higher than the levels permitted in the U.S.

Further systematic reviews have also addressed these concerns. The National Toxicology Program (NTP) conducted a systematic review of scientific literature regarding fluoride exposure, neurodevelopment, and cognition. The NTP found no evidence that fluoride exposure had adverse effects on adult cognition, based on studies measuring fluoride in urine or drinking water.

A corresponding meta-analysis on children’s IQ was published in JAMA Pediatrics on January 6, 2025. That analysis included 59 studies with group-level measures of fluoride exposure, though 47 of those studies were identified as having a high risk of bias.

Susan Fisher-Owens, a pediatrician at the University of California, San Francisco, noted that the recent U.S.-based research is a much needed addition to a broad literature that shows the safety and benefits of community water fluoridation and provides a stronger basis for making policy decisions.