Fluoride: Friend or Foe?

In recent years, renewed political and public attention has been drawn to the issue of water fluoridation and its potential effects on human health. Secretary of the Department of Health and Human Services Robert F. Kennedy Jr. has promised to remove fluoride from the country’s drinking water, calling it an “industrial waste” linked to a plethora of health problems and developmental disorders such as bone cancer, cognitive disorders, and arthritis. His statements reignited widespread debate about the safety of water fluoridation. While most public health experts have reaffirmed that the levels currently in U.S. drinking water are considered safe, many policymakers have begun making changes to local policies, most noticeably in Utah, which became the first state to ban the addition of fluoride to public drinking water following these renewed concerns.

The ninth element of the periodic table, fluoride, is a mineral found in the fruits and vegetables we eat, such as grapes, raisins, carrots, and potatoes. Also used in toothpaste, it strengthens tooth enamel, reversing tooth decay by a process called remineralization, promoting the build-up of calcium onto damaged areas of the teeth. Furthermore, because fluoride is highly electronegative, it can replace hydroxyl ions found in hydroxyapatite, the primary mineral in tooth enamel, to form fluorapatite, a more stable compound that is far more resistant to acidic damage.

Fluoride’s uses were first discovered in the early 1900s, when tooth decay was widespread and severe among many Americans. With the mass production of baked goods and processed foods, Americans were consuming far more refined sugar in their diet than ever before, all while having little to no knowledge of dental hygiene. It was during this time that Dentist Frederick McKay noticed that people living in Colorado had teeth that were surprisingly resistant to tooth decay. After careful research, McKay found that the reason for this resistance was Colorado’s water supply, which was rich in fluoride due to natural deposits in the area. In the years following, soluble fluoride-containing compounds such as sodium fluoride were shipped to water treatment plants, with automated dosing systems adding a precise amount to the water before being thoroughly mixed. The addition of fluoride to drinking water led to a steep decline in tooth decay and orthodontic diseases. Today, around 73 percent of American drinking water contains fluoride. 

Nevertheless, this miracle mineral has garnered a lot of controversy surrounding its potential risks. Some critics have claimed that because fluoride is already present in toothpaste, the chemical no longer needs to be added to drinking water. Opponents of water fluoridation, like RFK Jr., have also claimed the mineral may cause arthritis, neurodevelopmental disorders, and thyroid disease. Earlier this year, the National Institute of Health determined with moderate confidence that there is a link between higher levels of fluoride exposure and lower IQ in children. However, these trends are strong but are not enough to say for certain that there is a direct effect. Furthermore, the studies examined fluoride levels exceeding 1.5 mg/L, far above the CDC-recommended value. At these elevated levels, fluoride can interfere with normal thyroid function; as an inhibitor, fluoride competes with iodine for absorption, which can lead to iodine deficiency and hypothyroidism, a condition in which the thyroid gland does not produce enough hormones, leading to fatigue, weight gain, constipation, and dry skin. Additionally, overexposure to fluoride can lead to a condition known as skeletal fluorosis, which affects your bones and joints, causing pain, stiffness, and joint deformities. 

Mounting concerns over the dangers of high fluoride levels have led to action being taken. In 2015, the Department of Health and Human Services reduced the recommended level in U.S. community drinking water to less than 0.7 milligrams per liter to address the increased prevalence of dental fluorosis, noted by its distinctive white streaks on teeth. Due to the new 2015 regulations on the fluoridation of water, many dental epidemiologists argue that it is unlikely for someone to ingest enough to cause severe health problems like skeletal fluorosis, which causes joint stiffness and permanent bone deformities. Many researchers have thus investigated whether everyday exposure is sufficient to cause such conditions. Fatemeh Zohoori, a researcher at Teesside University, examined patients with cancers, cardiovascular disease, neurological disorders, and other chronic conditions, but did not find a statistically significant association between fluoride exposure at 0.7 mg/L and an increased risk of these diseases. 

However, some professors and scientists remain skeptical of fluoridated water, wondering if enough is being done to safeguard the next generation’s health. Philippe Grandjean, a professor of environmental health at the Harvard T.H. Chan School of Public Health, is one of them. “Lowering the recommended fluoridation level to 0.7 mg per liter is very well-justified. I would, in fact, recommend the level be reduced even further,” he says. “We need to revisit those benefits to make sure that the old reports [on fluoride’s role in dental protection] are still valid for the current exposure situation,” he adds. 

Dr. Ashley J. Malin from the University of Florida agrees. Her 2024 cohort study found associations between fluoride exposure and behavioral problems. Researchers in the study measured maternal urinary fluoride during the third trimester, with a median level of 0.76 mg/L, slightly above the CDC’s recommendation. They found that a 0.68 mg/L increase in maternal urinary fluoride was associated with nearly double the odds that young children develop neurobehavioral problems such as anxiety, depression, and social withdrawal, suggesting that “there may be a need to establish recommendations for limiting exposure from all sources during the prenatal period.”

Critics of the removal of fluoridated water, like the American Dental Association, however, point to real-world cases where the removal of fluoride has been followed by an increase in tooth decay. One notable real-world example comes from Calgary, Canada, where the city stopped adding fluoride to its drinking water in 2011. In the years following, there has been a 65 percent increase in tooth decay among children, larger than in nearby Edmonton, which continued fluoridation. After public outcry about the impact on lower-income families who may have limited access to dental care products, the city ultimately decided to reintroduce fluoride in public water sources in 2025 to help protect oral health across all communities.

Despite calls from RFK Jr. to end fluoridation nationwide, most communities in the U.S. continue to provide fluoridated drinking water. Although states like Utah have banned its addition into public water systems, it will take years to fully assess the long-term effects on dental health from such changes. Amid renewed attention on water fluoridation and public concerns, it remains clear that personal dental hygiene is the key to preventing tooth decay. Even in areas where fluoride remains in drinking water, individuals must practice regular brushing and flossing to maintain healthy teeth. As research continues to examine the potential risks and benefits of this mineral, people must take preventative measures to protect their overall dental health, regardless of policy changes.