A new study draws attention to potential issues with fluoride consumption. Share on Pinterest A new study looks at fluoride exposure in utero and the potential link to IQ. Getty Images The 70-year-old public health effort that saw water fluoridation become common in the United States is applauded by the Centers for Disease Control and Prevention (CDC) as one of the great achievements for public health in the 20th century. Currently, almost 75 percent of the population use fluoridated water from their local water systems. “Fluoride is a mineral that readily binds to bones and teeth. It’s typically used in dentistry to promote remineralization of dentin in the outer enamel of teeth,” explained Pamela Den Besten, DDS, MS, professor of orofacial sciences at University of California, San Francisco. We now take for granted that the addition of fluoride to public drinking water not only prevents tooth decay, but is also basically harmless. But now early research has brought up the possibility that fluoride could affect IQ levels in children exposed to the chemical in utero.

Prenatal fluoride exposure associated with lower IQ Researchers studied 512 children in Canada to find that those who were exposed to higher levels of fluoride before birth had significantly lower IQ scores between ages 3 and 4. The study was published today in JAMA Pediatrics. For the study, about 2,000 pregnant women from 10 cities across Canada were recruited from the Maternal-Infant Research on Environmental Chemicals (MIREC) program. The findings suggest that fluoride ingestion during pregnancy, within the normal range of water fluoridation standards, may affect children in utero. The study concluded that fluoride ingestion during pregnancy should be reduced while additional research is conducted. “To our knowledge, this study is the first to estimate fluoride exposure in a large birth cohort receiving optimally fluoridated water,” the study authors wrote.

Fluoride safety has long been debated Information on consumption of tap water and other water-based beverages, like tea and coffee, was obtained from a self-report questionnaire completed by mothers during the first and third trimesters. “Since the 1950s when water fluoridation began, its safety has been debated. We realized that there were major questions about the safety of fluoride, especially for pregnant women and young children. Decisions about safety need to be based on evidence,” study author Rivka Green, MA, a doctoral student in clinical developmental neuropsychology at York University, told Healthline. The study found the association of prenatal fluoride exposure with children’s lower IQ scores held up even after accounting for factors like the mother’s education, socioeconomic status, location, and exposure to other toxic metals. “Short of dosing women, we did everything we could to adjust for the factors that are typically controlled for in these types of studies. We studied an extensive list of other characteristics, like socioeconomic status and city, as well as other exposures, like lead, arsenic, and secondhand smoke, and our results remained,” Green said. Previous research led by York University researchers had already found that fluoride levels were twice as high for pregnant Canadian women living in cities where public drinking water is fluoridated compared to those in cities where the drinking water isn’t. “We found that fluoride in drinking water was the major source of exposure for pregnant women living in Canada. Women living in fluoridated communities have two times the amount of fluoride in their urine as women living in non-fluoridated communities,” Christine Till, PhD, an associate professor of psychology in York’s faculty of health and lead author of the study, said in a statement.

Findings agree with previous research This study adds to what we know from recent research that also found an association between prenatal exposure to fluoride and reduced intelligence. “Some previous studies showed that higher levels of fluoride were associated with lower IQ scores in children, including another prospective cohort study published in 2017 by the ELEMENT group, which found similar results to ours,” Green said. “However, our study was the first to look at prenatal exposure in a sample receiving optimally fluoridated water,” she emphasized.

Other potential fluoride issues According to Besten, who wasn’t involved with the new study, aside from the findings of these studies, consuming more than optimal amounts of fluoride can stain and weaken teeth. But consuming that much fluoride is unlikely to occur just from drinking tap water. “The most obvious effect of fluoride is the formation of fluorosed enamel. Fluorosis occurs when excess fluoride is present when the tooth is forming, and this excess fluoride results in hypomineralization [softening and discoloration of tooth enamel], which gives a whiter appearance to fluorosed, as compared to normal, enamel,” Besten said. She cautions that early research in animal studies have found a potential neurotoxic issue for high levels of fluoride. They “show that neurotoxicity of fluoride is related to the dose, timing of exposure, and sex of the individual,” Besten said. “More recent epidemiological research show associations between fluoride and neurotoxicity in humans,” she added.

Decades of use to stop tooth decay In an emailed statement to Healthline, Dr. Aparna Bole, FAAP, chair of the American Academy of Pediatrics (AAP) Council on Environmental Health, points out that community water fluoridation has helped decrease tooth decay for decades, and that this is one study that pointed toward correlation, not causation. “In most communities, tap water is a healthy and environmentally preferable choice,” Bole told Healthline. “This study is thought provoking, but the fact that results were different for boys and girls make them somewhat difficult to interpret, and fluoride intake in children was not examined.” Bole points out that the AAP supports community water fluoridation. “We support the public health sector’s continual evaluation of optimal community water fluoridation, and continue to recommend that children drink optimally fluoridated water,” Bole said. “In addition, children should use age-appropriate amounts of fluoride toothpaste with adult supervision, and have fluoride varnish applied to their teeth according to the US Preventive Task Force guidelines.”