Does Fluoride Lower the IQ?

By Elizabeth "Andie" Shin, DDS

Bethesda Chevy Chase Pediatric Dentistry

. https://bccpediatricdentistry.com/

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Does Fluoride Lower the IQ?

A pediatric dentist’s evidence-based look at what new studies are showing and how families can stay both cavity-free and safe.

What People Are Really Asking

When people hear about fluoride and IQ, most are not thinking about research papers or chemical names. They are thinking about the fluoride their children use every day, brushing their teeth, rinsing, or getting fluoride treatments at the dental office. That makes sense. But the studies that raised this question are not about fluoride that touches the teeth and gets spit out. They focus on fluoride that is swallowed, the kind that goes through the body in drinking water, baby formula mixed with tap water, and foods or beverages made with fluoridated water.¹ To understand the science, it helps to separate topical fluoride, which works on the surface of the tooth, from systemic fluoride, which travels through the bloodstream. Both play a role in oral health, but only the systemic kind is being studied for possible effects on the brain and body.

The Study That Reignited the Discussion

In early 2025, JAMA Pediatrics published a review combining 74 studies on fluoride exposure and children’s IQ.² The researchers found that, overall, children with higher fluoride levels in their bodies had slightly lower IQ scores. They did not claim fluoride directly causes lower IQ, but the link appeared stronger in studies that measured fluoride inside the body, such as urinary levels, rather than simply using city water data. Their message was straightforward. The pattern is strong enough to warrant a fresh look at how much fluoride children are receiving from all sources combined. Some academics have questioned the review, noting that many of the studies it included came from countries with higher natural fluoride levels or from communities with co-exposures such as arsenic or poor nutrition. Others have argued that the review’s methods may have combined studies of unequal quality. However, even among critics, there is general agreement that the findings raise valid questions and that more well-controlled research at U.S. exposure levels is urgently needed.

This Was Not the First Time Scientists Saw This

The JAMA study confirmed what earlier research had already noticed. In Canada (2019) pregnant women with higher urinary fluoride had children with slightly lower IQ scores, especially boys.³ In Mexico (2017–2018) two separate studies linked prenatal fluoride exposure with lower cognitive and attention scores.⁴⁻⁵ In Canada (2020) babies fed formula mixed with fluoridated tap water scored lower on non-verbal IQ tests than breastfed babies.⁶ Earlier reviews (2012–2018) also showed an inverse relationship between fluoride exposure and IQ, though quality varied.⁷ In New Zealand (2015) one study found no difference, but it used residence rather than biomarkers to estimate exposure.⁸ Taken together, this growing body of evidence suggests a consistent pattern that deserves attention, especially for developing brains.

Beyond IQ: Other Health Clues

Even if we set aside brain development, fluoride that is swallowed leaves unmistakable signs inside the body. The most visible sign is dental fluorosis, faint white lines, cloudy patches, or brownish streaks that appear on teeth as they form. Many professionals call it a cosmetic issue, but that view misses the deeper biological meaning. Fluorosis is not merely a surface change; it is a biological warning sign of overexposure.⁹ It tells us that, during tooth development, the body absorbed more fluoride than it could safely manage. At that point, the safe threshold for cellular balance has already been surpassed. Because fluoride is strongly attracted to calcium, it tends to settle in tissues rich in calcium, including teeth, bones, the pineal gland, and even developing regions of the brain.¹⁰ The enamel changes we can see are simply the visible tip of a deeper metabolic shift. The same chemical interactions that create white streaks in enamel may also be occurring silently in the thyroid, kidneys, and nervous system, where we cannot see them with the naked eye.¹¹ Fluorosis, therefore, should not be dismissed as cosmetic. It is the body’s way of signaling that fluoride exposure has reached a level capable of altering normal cellular activity. The teeth are the dashboard light, and once they show a warning, the rest of the system deserves inspection.

Topical Fluoride: Still a Trusted Ally

Fluoride that stays on the tooth surface remains one of dentistry’s most effective tools. Toothpaste, varnish, and sealants all work topically to harden enamel and prevent decay.¹² The question today is not whether fluoride works, but how much and how it is delivered. In the 1950s, when toothpaste was rare, water fluoridation helped communities reduce cavities. Now, with widespread fluoride toothpaste, professional varnish, and better nutrition, mass ingestion may no longer add much benefit and could increase total exposure unnecessarily.¹³ Modern prevention should be targeted rather than universal ingestion.

Practical Questions People Are Asking About Fluoride

1. If fluoride helps teeth, why are people suddenly worried about it? Because scientists are now examining how swallowed fluoride affects other organs besides teeth. Fluoride is beneficial in small amounts, but it can accumulate in bones and tissues. Researchers are exploring its possible influence on the brain, thyroid, and kidneys.¹⁴ The goal is balance, not elimination.

2. How can parents protect their children without overdoing fluoride? Use toothpaste properly: rice-sized for toddlers, pea-sized for preschoolers, and teach them to spit, not swallow.¹⁵ Professional fluoride varnish and sealants are safe and stay on the teeth. When preparing baby formula, alternate between fluoridated and low-fluoride bottled or filtered water.⁶ Good brushing and diet remain the best cavity prevention.

3. Is fluoridated water safe during pregnancy? Pregnancy is a sensitive time for brain and organ development. Expectant mothers can use reverse-osmosis or carbon filters for drinking water, mix bottled and filtered water to reduce total intake, and maintain gum health since inflammation during pregnancy can affect the baby.¹⁶ Lowering ingestion is a reasonable precaution, not an alarm.

4. What about adults with kidney or thyroid conditions? People with reduced kidney function clear fluoride more slowly, so it can accumulate.¹⁷ Those with thyroid disorders may also be more sensitive. Choose filtered or non-fluoridated water when possible. Continue using fluoride toothpaste since it acts topically. Inform your doctor about local water fluoridation to help interpret labs.¹⁸ Fluoride is not automatically harmful, but those with chronic illness should manage intake carefully.

5. Are fluoride-removing filters expensive? Not really. Reverse-osmosis systems cost about $150–300 with annual filter changes, and smaller countertop models start near $50.¹⁹ For families with infants or chronic illness, it is a practical safeguard.

6. How can I find out if my water has fluoride? Check your city’s annual water report or the CDC’s “My Water’s Fluoride” website. If you use a private well, have it tested, since natural levels vary widely.²⁰

7. Does bottled water contain fluoride? Some brands do and others do not. Always read the label. For baby formula, most pediatricians suggest non-fluoridated bottled or filtered water.²¹

8. What is the safest overall approach? Keep topical fluoride such as toothpaste, varnish, and sealants. Reevaluate systemic exposure during pregnancy, infancy, or chronic illness. Support new U.S.-based studies that measure real fluoride levels instead of relying on decades-old data.²² Fluoride’s value remains, but dose and delivery are what truly determine safety.

So, Does Fluoride Lower IQ?

The fair answer is that higher systemic fluoride exposure is associated with slightly lower IQ in many studies.²⁻⁶ At typical U.S. fluoridation levels, the data are still limited. Topical fluoride remains safe and effective. In short, keep fluoride on the teeth, not in the bloodstream.

A Final Word

Community water fluoridation was one of the great health achievements of the twentieth century. Yet children today already receive fluoride from toothpaste, varnish, and food. We can preserve its benefits while reducing unnecessary ingestion. Re-examining systemic fluoride is not anti-science; it is good science. Our responsibility is to use fluoride wisely, to protect both smiles and developing minds. If you have questions about fluoride or your child’s oral health, you are welcome to email me at smile@bccpediatricdentistry.com. I am always happy to help families make informed, confident choices.

Reference Index

1. CDC. Community Water Fluoridation Factsheet. 2023.

2. Taylor PJ et al. Fluoride Exposure and Children’s IQ Scores: A Systematic Review and Meta-analysis. JAMA Pediatrics. 2025.

3. Green R et al. Association Between Maternal Fluoride Exposure and IQ in Children. JAMA Pediatrics. 2019.

4. Bashash M et al. Prenatal Fluoride Exposure and Cognitive Outcomes. Environmental Health Perspectives. 2017.

5. Thomas D et al. Fluoride Exposure and ADHD-like Symptoms in Children. Environment International. 2018.

6. Till C et al. Fluoride Exposure from Infant Formula and Nonverbal IQ. Environment International. 2020.

7. Choi AL et al. Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis. Environmental Health Perspectives. 2012.

8. Broadbent JM et al. Community Water Fluoridation and Intelligence: New Zealand Cohort Study. American Journal of Public Health. 2015.

9. DenBesten PK, Li W. Chronic Fluoride Toxicity: Dental Fluorosis and Beyond. Toxicology. 2011.

10. Luke J. Fluoride Deposition in the Aged Human Pineal Gland. Caries Research. 2001.

11. NRC (National Research Council). Fluoride in Drinking Water: A Scientific Review of EPA’s Standards. 2006.

12. Walsh T et al. Fluoride Toothpastes for Preventing Dental Caries in Children and Adults. Cochrane Database Syst Rev. 2019.

13. Iheozor-Ejiofor Z et al. Water Fluoridation for the Prevention of Dental Caries. Cochrane Database Syst Rev. 2015.

14. Grandjean P. Developmental Fluoride Neurotoxicity: An Updated Review. Environmental Health. 2019.

15. American Dental Association. Fluoride Toothpaste Use for Young Children. ADA Council on Scientific Affairs, 2024.

16. NTP Monograph on Fluoride Exposure and Neurodevelopmental and Cognitive Effects. U.S. HHS, 2024.

17. Barbier O et al. Molecular Mechanisms of Fluoride Toxicity in Animals and Humans. Chemico-Biological Interactions. 2010.

18. Peckham S et al. Fluoride and the Thyroid: A Review of the Literature. Journal of Epidemiology & Community Health. 2015.

19. NSF International. Home Water Treatment Devices and Fluoride Removal Efficiency. 2022.

20. CDC. My Water’s Fluoride Database. 2024.

21. U.S. FDA. Bottled Water Standards and Labeling for Fluoride. 2023.

22. NASEM Report. Research Gaps in Low-Exposure Fluoride Studies. 2024.