References and Sources

Little Things Matter: The Impact of Fluoride on Brain Development

For years, we were led to believe that fluoride is safe. (1,2)


Is fluoride really safe?

Let’s look at what we’ve learned over the past century.

In the 1930s, a dentist discovered that children who drank water with naturally high levels of fluoride had fluorosis – the staining or mottling of teeth. (4)

Children with fluorosis had about 5 fewer cavities than children without fluorosis. (5)

Next, scientists showed that adding fluoride to drinking water led to less tooth decay. (5)

Unfortunately, tooth mottling increased as more fluoride was added to water. (5,6) 

The optimal range or “sweet spot” to prevent tooth decay and minimize mottling was about 1 ppm. (5)

Meanwhile, the sugar industry, which knew sugar caused tooth decay, promoted the use of fluoride and mounted a campaign to thwart efforts to reduce sugar consumption. (7)

Then, beginning in the 1970s, soon after fluoride was added to toothpaste, cavities declined sharply in countries with water fluoridation. (8)

But they also declined in countries without fluoridation. (8)

Today, about 75% of Americans (9) and 38% of Canadians (10) drink fluoridated water.[1]

A new study showed that water fluoridation prevents about one cavity per child. (11)

Still, over 90% of Americans have tooth decay. (12)

Meanwhile, scientists began to find clues that fluoride was toxic to the developing brain. (13–15)

Everybody agrees that fluoride is toxic at very high levels. (16)

What about lower levels?

In over a dozen studies – mostly from China – children who lived in villages with naturally high levels of fluoride had about 7 fewer IQ points than children in other villages. (15)

 But those levels were somewhat higher than those found in North America.

Two newer studies of pregnant women and their children – one in Mexico (17), where fluoride is added to salt, and other one in Canada (18), where fluoride is added to water – also found that fluoride led to IQ deficits in children.

As fluoride levels increased in pregnant women from .1 ppm to 1 ppm, the IQ scores of their children dropped, by about 3 to 5 points. (17,18)

What about infants?

As fluoride increased in infants, their IQ scores dropped further, especially in formula-fed babies. (19) 

Infants who are fed formula made with fluoridated tap water ingest more fluoride than a breasted infant; breastmilk contains low amounts of fluoride. (20–25)

Some critics say that because our study was an observational study – we didn’t dose pregnant women with fluoride, like a drug study – it was inconclusive. (26)

But if we dismissed all observational studies, we would have little evidence that water fluoridation prevents tooth decay. (27)

Some critics say it is only one study. (26,28)

But that ignores over a dozen high-quality studies showing that fluoride is toxic to the developing brain. (29,30)

Some critics say it is of little consequence if a child loses 3 to 5 IQ points. (26)

Is it worth losing 5 IQ points to prevent one cavity?

Let’s look at the impact of reducing children’s IQ score by 5 points.

Most of us have IQ scores that fall between 85 and 115 points. (31)

Only 2.5% of children have an IQ above 130, which is considered gifted. There are about 6 million children in this group. (32)

On the other end of the distribution, another 2.5% of children have an IQ below 70, which is considered “challenged.” (32)

A 5-point drop in IQ results in a 57% increase in the number of children that are challenged, from 6 million to 9.4 million.

There is a corresponding decrease in the number of children that are gifted, from 6 million to 2.4 million. (33)

What’s more, children are often to exposed to many chemicals that impair brain development – like lead, air pollution, pesticides and fluoride. The impact of 3 or 4 toxic chemicals adds up and greatly increases the number of children who are challenged. (34)

What can you do?

Pregnant women and infants should reduce fluoride intake. After all, it only benefits children once their teeth have erupted.(35)

If you are pregnant, don’t drink fluoridated water or black tea.[2] (36)

If possible, breastfeed your baby. (37,38)

Otherwise, don’t use fluoridated water to make infant formula. (19)

Children should only use a rice-sized amount of toothpaste when they brush their teeth, not the amount shown on toothpaste commercials and they shouldn’t swallow it. (39)

Adding fluoride to water isn’t the only way to prevent cavities.

You can choose not to buy products from companies that market sweetened drinks and highly processed foods to children. After all, sugar is the main cause of tooth decay. (7)


1. Allukian Jr, M., Carter-Pokras, O.D., Gooch, B.F., Horowitz, A.M., Iida, H., Jacob, M., Kleinman, D.V., Kumar, J., Maas, W.R., Pollick, H., Rozier, R.G. (2018). Science, politics, and communication: The case of community water fluoridation in the US. Annals of epidemiology, 28(6), 401–410. 10.1016/j.annepidem.2017.05.014

2. Zelko, F. (2019). Optimizing nature: Invoking the “natural” in the struggle over water fluoridation. History of Science, 57(4), 518-539. 10.1177/0073275318809764

3. Nightair (2013, September 27). The Fluoride Deception (Interview) [Video file]. YouTube,

4. Smith, F.C. (1916). Mottled enamel and brown stain: A condition affecting the teeth in certain localities. Public Health Reports (1896-1970), 31(42), 2915–2918. 10.2307/4574196

5. Dean, H.T., Arnold, F.A., Jr. Elvove, E. (1942). Domestic water and dental caries. V. Additional studies of the relation of fluoride domestic waters to dental caries experience in 4,425 white children, aged 12 to 14 years, of 13 cities and 4 States. Public Health Reports (1896-1970), 57(32), 1155-1179. 10.2307/4584182

6. Leverett, D. (1986). Prevalence of dental fluorosis in fluoridated and nonfluoridated communities—a preliminary investigation. Journal of public health dentistry, 46(4), 184–97. 10.1111/j.1752-7325.1986.tb03140.x

7. Kearns, C.E., Glantz, S.A., Schmidt, L.A. (2015). Sugar industry influence on the scientific agenda of the national institute of dental research’s 1971 National Caries Program: A historical analysis of internal documents. PLos Med, 12(3), 1–22. 10.1371/journal.pmed.1001798

8. Marthaler, T.M. (2004). Changes in dental caries 1953-2003. Caries research, 38(3), 173–81. 10.1159/000077752

9. U.S. Department of Health and Human Services Federal Panel on Community Water Fluoridation. (2015). U.S. Public Health Service recommendation for fluoride concentration in drinking water for the prevention of dental caries. Public Health Reports, 130(4), 318-331. 10.1177/003335491513000408

10. Public Health Agency of Canada. (2017). The state of community water fluoridation (CWF) across Canada.

11. Slade, G.D., Grider, W.B., Maas, W.R., Sanders, A.E. (2018). Water fluoridation and dental caries in U.S children and adolescents. Journal of dental research, 97(10), 1122-1128. 10.1177/0022034518774331

12. Centers for Disease Control and Prevention. (2019). Oral Health Surveillance Report: Trends in Dental Caries and Sealants, Tooth Retention, and Edentulism, United States, 1999–2004 to 2011–2016. Atlanta, GA: Centers for Disease Control and Prevention, US Dept of Health and Human Services.

13. National Research Council (NRC). (2006). Fluoride in Drinking Water: A Scientific Review of EPA’s Standards. Washington, DC: National Academies Press.

14. Mullenix, P.J., Denbesten, P.K., Schunior, A., Kernan, W.J. (1995). Neurotoxicity of sodium fluoride in rats. Neurotoxicology and teratology, 17(2), 169–77.                               10.1016/0892-0362(94)00070-T

15. Choi, A.L., Sun, G., Zhang, Y., Grandjean, P. (2012). Developmental fluoride neurotoxicity: A systematic review and meta-analysis. Environmental Health Perspectives, 120(10), 1362–1368. 10.1289/ehp.1104912

16. Gessner, B.D., Beller, M., Maddaugh, J.P., Whitford, G.M. (1994). Acute fluoride poisoning from a public water system. New England Journal of Medicine, 330(2), 95-99. 10.1056/NEJM199401133300203

17. Bashash, M., Thomas, D., Hu, H., Martinez-Mier, E.A., Sanchez, B.N., Basu, N., Peterson, K.E., Ettinger, A.S., Wright, R., Zhang, Z., Liu, Y., Schnaas, L., Mercado-García, A., Téllez-Rojo, M.M., Hernández-Avila, M. (2017). Prenatal fluoride exposure and cognitive outcomes in children at 4 and 6 – 12 years of age in Mexico. Environmental Health Perspective, 125(9), 1-12. 10.1289/EHP655

18. Green, R., Lanphear, B., Hornung, R., Flora, D., Martinez-Mier, E.A., Neufeld, R., Ayotte, P., Muckle, G., Till, C. (2019). Fluoride exposure during fetal development and intellectual abilities in a Canadian birth cohort. JAMA Pediatrics, 173(10), 940-948. 10.1001/jamapediatrics.2019.1729

19. Till, C., Green, R., Flora, D., Hornung, R., Martinez-Mier, EA., Blazer, M., Farmus, L., Ayotte, P., Muckle, G., Lanphear, B. (2020). Fluoride exposure from infant formula and child IQ in a Canadian birth cohort. Environmental International, 134, 105315. 10.1016/j.envint.2019.105315

20. Dabeka, R.W., Karpinski, K.F., McKenzie, A.D., Bajdik, C.D. (1986). Survey of lead, cadmium and fluoride in human milk and correlation of levels with environmental and food factors. Food Food and chemical toxicology, 24(9), 913-921. 10.1016/0278-6915(86)90318-2

21. Ekstrand, J., Boreus, L.O., de Chateau, P. (1981). No evidence of transfer of fluoride from plasma to breast milk. British medical journal (Clinical research ed.), 283(6294), 761–762. 10.1136/bmj.283.6294.761

22. Ekstrand, J., Hardell, L., Spak, C. (1984). Fluoride balance studies on infants in a 1-ppm-water-fluoride area. Caries research, 18(1), 87–92. 10.1159/000260753

23. Esala, S., Vuori, E., Helle, A. (1982). Effect of maternal fluorine intake on breast milk fluorine content. British journal of nutrition, 48(2), 201-204. 10.1079/BJN19820105

24. Faraji, H., Mohammadi, A. A., Akbari-Adergani, B., Saatloo, N. V., Lashkarboloki, G., Mahvi, A. H. (2014). Correlation between fluoride in drinking Water and its levels in breast milk in Golestan Province, Northern Iran. Iranian Journal of Public Health, 43(12), 1664-1668.

25. Zohoori, F. V., Omid, N., Sanderson, R. A., Valentine, R. A., & Maguire, A. (2019). Fluoride retention in infants living in fluoridated and non-fluoridated areas: effects of weaning. British Journal of Nutrition, 121(1), 74-81. 10.1017/S0007114518003008

26. Science Media Center. (2019, August 19). Expert reaction to study looking at maternal exposure to fluoride and IQ in children.

27. Iheozor-Ejiofor, Z., Worthington, H.V., Walsh, T., O’Malley, L., Clarkson, J.E., Macey, R., Alam, R., Tugwell, P., Welch, V., Glenny, A. (2015). Water fluoridation for the prevention of dental caries. Cochrane Database of Systematic Reviews, 2015(6), CD010856. 10.1002/14651858.CD010856.pub2

28. Burger, D., Garvin, J. (2019, August 27). Responses to fluoride study flood in from all over the globe. American Dental Association.

29. NTP. (2019). Draft NTP Monograph on the Systematic Review of Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects.

30. Grandjean, P. (2019). Developmental fluoride neurotoxicity: an updated review. Environmental Health, 18(1), 1-17. 10.1186/s12940-019-0551-x

31. Wechsler, D. (1999). Manual for the Wechsler abbreviated intelligence scale (WASI). San Antonio, TX: The Psychological Corporation.

32. Sattler J.M. (2008). Assessment of children: Cognitive foundations (5th ed). La Mesa, California: Sattler, Publisher, Inc.

33. Lanphear, B. P., Vorhees, C. V., Bellinger, D. C. (2005). Protecting children from environmental toxins. PLoS Med, 2(3), e61. 10.1371/journal.pmed.0020061

34. Lanphear, B. P. (2015). The impact of toxins on the developing brain. Annual Review of Public Health, 36(1), 211-230. 10.1146/annurev-pubhealth-031912-114413

35. Limeback, H. (1999). A re‐examination of the pre‐eruptive and post‐eruptive mechanism of the anti‐caries effects of fluoride: is there any anti‐caries benefit from swallowing fluoride?. Community dentistry and oral epidemiology, 27(1), 62-71. 10.1111/j.1600-0528.1999.tb01993.x

36. Rodríguez, I., Burgos, A., Rubio, C., Gutiérrez, A. J., Paz, S., da Silva Júnior, F. M. R., Hardisson, A., Revert, C. (2020). Human exposure to fluoride from tea (Camellia sinensis) in a volcanic region—Canary Islands, Spain. Environmental Science and Pollution Research, 1-12. 10.1007/s11356-020-10319-9

37. Jeffrey, N., Canadian Paediatric Society, Nutrition and Gastroenterology Committee. (2013). Nutrition for healthy term infants, birth to six months: An overview. Paediatrics & Child Health, 18(4), 206-207. 10.1093/pch/18.4.206

38. Eidelman A.I, Schnaler, R.J. (2012). Breastfeeding and the use of human milk. Pediatrics, 129(3), e827–841. 10.1542/peds.2011-3552

39. Thornton-Evans, G., Junger, M. L., Lin, M., Wei, L., Espinoza, L., & Beltran-Aguilar, E. (2019). Use of Toothpaste and Toothbrushing Patterns Among Children and Adolescents—United States, 2013–2016. Morbidity and Mortality Weekly Report, 68(4), 87-90. 10.15585/mmwr.mm6804a3

[1] These numbers are based on the American and Canadian population on community water systems.

[2] Black teas have high concentrations of natural fluoride due to the accumulation of fluoride in tea leaves from the soil (Fung et al., 1999).


View all posts