“I heard fluoride lowers IQ in children. Should I stop giving my child tap water to drink?”
This is one of those questions that can make you pause mid-sip of your water.
Fluoride has been added to community drinking water for decades to prevent cavities. It’s considered one of our great public health successes. But recently, fluoride has been making headlines for a different reason: concerns about its possible effects on children’s cognitive development.
Those concerns intensified after a 2025 JAMA Pediatrics meta-analysis⁵ found an association between higher fluoride exposure and lower children’s IQ scores.
So…should we be worried?
The short answer: The research deserves our attention, but we don’t currently have evidence that fluoride at the level used in U.S. community water fluoridation lowers IQ.
For the deeper dive, listen to our August episode of Hippo Education Presents: The Monthly Rounds: “Fluoride and IQ: Clearing the Confusion.” Dr. Michael Mett and I unpack the history of fluoridation, the recent IQ research, and what the evidence actually means for clinicians counseling families.
Fluoride occurs naturally in water, soil, and foods. And we’ve known for nearly a century that fluoride can protect teeth from cavities. In the early 1900s, researchers noticed that communities with naturally high fluoride levels had fewer cavities — but also more dental fluorosis, or discoloration of the teeth.
That observation eventually led to the intentional fluoridation of community water. In 1945, Grand Rapids, Michigan, became the first U.S. city to fluoridate its water supply, and early studies found substantial reductions in dental caries among children.
Today, fluoride toothpaste is widespread and access to dental care has improved, so the benefit of fluoridated water isn't as dramatic as it once was. But it remains an important tool for preventing tooth decay.
And that brings us to the question families are asking now: Could that benefit come with a cost to children's brain development?
Here’s where things get complicated.
The 2025 JAMA Pediatrics systematic review and meta-analysis included 74 studies examining total fluoride exposure and children’s IQ. Overall, researchers found that higher fluoride exposure was associated with lower IQ scores.
But before we toss our tap water, we need to look at where those data came from and what fluoride exposures were actually being studied. A few important points:
None of the studies were conducted in the United States. Most of the studies were conducted in countries such as China, India, Iran, Mexico, and Pakistan. Many of the studies involved fluoride exposures substantially higher than the 0.7 mg/L used for U.S. community water fluoridation
Many studies had a high risk of bias. Of the 74 included studies, 52 were classified as having a high risk of bias. Many were cross-sectional, and exposure assessment varied significantly.
The studies measured fluoride levels in different ways. Some studies measured fluoride in local drinking water. Others used urinary fluoride, sometimes from a single spot urine sample, which may tell you more about recent exposure than someone’s total fluoride exposure.
There are also many factors besides fluoride that affect a child’s cognitive development: lead and other environmental exposures, nutrition, socioeconomic factors, access to healthcare, and more. Controlling perfectly for all those variables is… not easy.
Importantly, when the researchers restricted their main drinking-water analysis to fluoride concentrations below 1.5 mg/L, the overall association with IQ was no longer statistically significant. The authors concluded that data at these lower water concentrations were limited and that uncertainty remained.
That doesn’t mean we should ignore the findings. It means we need to be careful about extrapolating them to a different population at a substantially different exposure.
The U.S. Public Health Service recommends a fluoride concentration of 0.7 mg/L in community water systems. This level was selected to provide the dental benefits of fluoride while minimizing potential harms such as dental fluorosis.
The Environmental Protection Agency (EPA) sets a secondary standard of 2.0 mg/L for fluoride, a threshold intended to limit dental fluorosis. The legally enforceable maximum concentration is 4.0 mg/L.
For the most part, U.S. community water systems are doing a pretty good job of hitting those targets. CDC data from 2016–2021⁴ found that:
More than 80% of fluoride measurements from reporting community water systems were above 0.6 mg/L
16.3% had fluoride levels below 0.6 mg/L
99.99% were below 2.0 mg/L
So while not every water system is perfectly optimized for the target level, fluoride concentrations above 2.0 mg/L appear to be very uncommon.
So what do we see when we look specifically at U.S. data? Two recent studies examined cognitive outcomes in U.S. populations exposed to fluoride at levels relevant to community water fluoridation.
A 2025 study by Warren et al³ analyzed data from a large, nationally representative cohort of U.S. students. It found no evidence that exposure to recommended fluoride levels was associated with worse cognitive outcomes. In fact, children exposed to recommended fluoride levels had slightly higher scores on some cognitive measures during the school years, although this difference did not persist into later adulthood.
A second study,² published by Warren et al. in 2026, used decades of data from Wisconsin communities with and without fluoridated water. Researchers found no evidence that community water fluoridation was associated with lower IQ during adolescence or poorer cognitive outcomes later in adulthood.
So while continued research is appropriate — especially prospective research at fluoride levels relevant to U.S. communities — the current evidence indicates that fluoridation at recommended levels in the US is not linked to adverse cognitive outcomes.
There’s another piece of this risk-benefit equation that can get lost in conversations about potential harms: What happens if we remove fluoride?
We actually have some data on that.
Juneau, Alaska, stopped fluoridating its community water in 2007. Researchers later examined Medicaid dental claims¹ before and after fluoridation ended. Among young children born after fluoridation stopped, cavity-related dental procedures and annual dental treatment costs increased, with the greatest impact among children from lower socioeconomic backgrounds, potentially widening existing health disparities.
And the consequences of reduced access to fluoride can extend well beyond oral health. Dental disease can mean pain, infection, missed school, missed work for parents, difficulty eating, and sometimes sedation or general anesthesia to complete extensive dental work.
So when we're weighing potential risks of fluoride, it's important to consider both sides of the equation.
When families ask about fluoride, we don't need to give them a crash course in epidemiology. A few simple messages can go a long way:
Start with the concern: “It’s reasonable to ask about something your child is exposed to every day. The headlines about fluoride and IQ have raised legitimate questions.”
Put the evidence in context: “The studies raising the most concern generally involved higher fluoride exposures than what we see with U.S. community water fluoridation. Current U.S. data have not shown evidence that fluoridation at 0.7 mg/L lowers IQ.”
Keep the focus on dental health: “Fluoride is one of the tools we use to prevent cavities, and preventing cavities is part of keeping kids healthy.”
Bring it back to the big picture: “Based on what we know today, there’s no reason to avoid fluoridated tap water because of concerns about IQ.”
Want the deeper dive? Listen to “Fluoride and IQ: Clearing the Confusion” on The Monthly Rounds on Spotify or Apple Podcasts.
References:
McLaren L, Patterson SK, Faris P, et al. Fluoridation cessation and children's dental caries: a 7-year follow-up evaluation of Grade 2 schoolchildren in Calgary and Edmonton, Canada. Community Dent Oral Epidemiol. 2022;50(5):391-403. doi:10.1111/cdoe.12685
Warren JR, Rumore G, Sicinski K, Herd P, Engelman M. Municipal water fluoridation, adolescent IQ, and cognition across the life course: evidence from the Wisconsin Longitudinal Study. Proc Natl Acad Sci U S A. 2026;123:e2536005123. doi:10.1073/pnas.2536005123
Warren JR, Rumore G, Kim S, et al. Childhood fluoride exposure and cognition across the life course. Sci Adv. 2025;11(47):eadz0757. doi:10.1126/sciadv.adz0757
Boehmer TJ, Lesaja S, Espinoza L, Ladva CN. Community water fluoridation levels to promote effectiveness and safety in oral health—United States, 2016–2021. MMWR Morb Mortal Wkly Rep. 2023;72(22):593-596. doi:10.15585/mmwr.mm7222a1
Taylor KW, Eftim SE, Sibrizzi CA, et al. Fluoride exposure and children's IQ scores: a systematic review and meta-analysis. JAMA Pediatr. 2025;179(3):282-292. doi:10.1001/jamapediatrics.2024.5542