Fluoride Action Network

Summary of 2011 Fluoride Research

Fluoride Action Network | By Tara Blank, PhD

Fluoride and Brain Damage

Evidence of fluoride’s detrimental effects on the brain and central nervous system continues to mount. Among animal studies, chronic fluoride exposure in rats has been found to result in: detrimental changes in the sciatic nerve, spinal cord, and hippocampus and neocortex of the brain (Reddy et al., 2011); changes in the expression of several brain proteins, including those involved with cell signaling, energy metabolism, and protein metabolism (Ge et al., 2011); and changes in the structure and function of the synaptic interface, which would likely result in altered transmission of neural information (Zhu et al., 2011).

At least four more studies finding a link between fluoride exposure and decreased intelligence (IQ) of children were published this year, putting the total number of such studies at 25. Poureslami et al. (2011) found that children 7-9 years old living in a “high” fluoride city (2.38 mg F/L in drinking water) had significantly lower IQ scores than those living in a “low” fluoride city (0.41 mg F/L in drinking water). A previous study (Poureslami et al., 2010) had found that children 4-5 years old living in this “high” fluoride city had a daily fluoride intake of 1.71 mg. Frighteningly, this is actually less than than the average daily intake for similarly aged children in the United States (2.03 mg/day), according to a recent analysis by the U.S. EPA (2010).

Another study similarly found a trend towards decreasing IQ in 12-14 year old children living in a “high” fluoride village (2.45 mg F/L in drinking water), compared to those living in a “low” fluoride village (0.29 mg F/L in drinking water) (Eswar et al., 2011). Taking a different approach, a study by Shivaprakash et al. (2011) found that the mean IQ score of 7-11 year-old children with dental fluorosis (66.6) was significantly lower than those without dental fluorosis (76.4), with girls being more negatively impacted than boys. Another study by Ding et al. (2011) found a very significant association between fluoride levels in children’s urine and IQ scores, with an estimated 0.59 IQ points lost for each 1 mg/L increase in urinary fluoride. It is again disturbing that similar urine fluoride levels have been observed in children (NRC, 2006) consuming what is considered the average amount of fluoride ingested by children in fluoridated communities (EPA, 2010).

Two reviews on the neurotoxicity of fluoride were also published this year. According to Valdez-Jiménez (2011), “The prolonged ingestion of [fluoride] may cause significant damage to health and particularly to the nervous system. Therefore, it is important to be aware of this serious problem and avoid the use of toothpaste and items that contain [fluoride], particularly in children as they are more susceptible to the toxic effects of [fluoride].” Spittle (2011) concluded “there is no threshold for fluoride neurotoxicity in drinking water, and the only assuredly safe level is zero.”

Other Effects of Fluoride

In addition to neurological damage, studies published this year have also found that exposure to fluoride can lead to:

  • Structural damage of the renal cortex (kidney) of female mice (Abdo et al., 2011)
  • Reduced viability of bone-forming cells (osteoblasts) (Yang et al. 2011)
  • Reduced ability of bone cells (osteocytes) to respond to mechanical usage (Willems et al., 2011)
  • Insulin resistance in rats (Lupo et al., 2011). These rats had a plasma fluoride level similar to those found in humans consuming an “average” amount of fluoride from fluoridated water and other sources (EPA, 2010).
  • Dental fluorosis, signifying fluoride overexposure:
    • Amoxicillin, an antibiotic frequently prescribed for children, was found to increase the risk of fluorosis on permanent teeth when used by children 20-24 months old (Hong et al., 2011).
    • More severe forms of fluorosis were observed when rats were exposed to both fluoride and lead (Leite et al., 2011). Silicofluorides, which are used in 90% of water fluoridation schemes in the U.S., have been associated with increased blood lead levels in children (Masters et al., 2000), and thus may be contributing to the prevalence of dental fluorosis among children in this country.
    • In addition to respiratory and digestive problems, patients with cystic fibrosis (CF) may also suffer from enamel defects. These defects are the result of protein retention in mature enamel, similar to dental fluorosis brought on by excess fluoride consumption. Duan et al. (2011) found that excess fluoride disrupts cellular processes related to the gene that is defective in CF patients. Thus, fluoride may worsen the symptoms of CF patients, and may even induce CF-like symptoms in those without CF.
    • Infants consuming formula made with fluoridated water are at an increased risk for developing dental fluorosis (Berg et al., 2011). A panel of the American Dental Association concluded “The estimated risk of enamel fluorosis related to fluoride intake from reconstituted infant formula is associated with the fluoride concentration in the drinking water.” The panel offered the following recommendation to practitioners: “When the potential risk of enamel fluorosis development is a concern, suggest ready-to-feed formula or powdered or liquid concentrate formula reconstituted with water that is either fluoride free or has low concentrations of fluoride.”

A Note on Fluoride and Osteosarcoma

In 2006 a study by Elise Bassin was published in the journal Cancer Causes and Control, which found an increased risk for osteosarcoma (an aggressive form of bone cancer) in boys exposed to fluoridated water in their 6th to 8th years (Bassin et al., 2006). Chester Douglass, Bassin’s Harvard thesis advisor, had promised that his group would publish another study that would disprove Bassin’s findings. Five years later that study finally appeared, in a dental journal (Journal of Dental Research). This study (Kim et al., 2011) investigated the association between bone fluoride levels and incidence of osteosarcoma. However, contrary to the accolades of fluoride proponents, this study had major flaws and was incapable of refuting the findings of Bassin. For a more in-depth analysis of the Kim et al. (2011) study, follow this LINK.


Abdo FK, Khalifa ME, Zidan RA, Abdel Aal SM. 2011. Effect of sodium fluoride-induced toxicity on the renal cortex of lactating mice and their offspring: a light and electron microscopic study. Egypt J Hist 34(3):554-65.

Bassin EB, Wypij D, Davis RB, Mittleman MA. 2006. Age-specific fluoride exposure in drinking water and osteosaroma (United States). Cancer Causes Control 17(4):421-8.

Berg J, Gerweck C, Hujoel PP, King R, Krol DM, Kumar J, Levy S, Pollick H, Whitford GM, Strock S, Aravamudhan K, Frantsve-Hawley J, Meyer DM. 2011. Evidence-based clinical recommendations regarding fluoride intake from reconstituted infant formula and enamel fluorosis. JADA 142(1):79-87.

Ding Y, Sun YGH, Han H, et al. 2011. The relationships between low levels of urine fluoride on children’s intelligence, dental fluorosis in endemic fluorosis areas in Hulunbuir, Inner Mongolia, China. J Haz Mat 186(2-3):1942-6.

Duan X, Mao Y, Wen X, Yang T, Xue Y. 2011. Excess fluoride interferes with chloride-channel-dependent endocytosis in ameloblasts. J Dent Res 90(2):175-80.

EPA (U.S. Environmental Protection Agency). 2010. Fluoride: Exposure and Relative Source Contribution Analysis. Office of Water, Office of Science and Technology, Health and Ecological Criteria Division. 820-R-10-015.

Eswar P, Nagesh L, Devaraj CG. 2011. Intelligence quotients of 12-14 year old school children in a high and a low fluoride village in India. Fluoride 44(3):168-72.

Ge Y, Niu R, Zhang J, Wang J. 2011. Proteomic analysis of brain proteins of rats exposed to high fluoride and low iodine. Arch Toxicol 85:27-33.

Hong L, Levy SM, Warren JJ, Broffitt B. 2011. Amoxicillin use during early childhood and fluorosis of later developing tooth zones. J Publ Health Dent 71(3):229-35.

Kim FM, Hayes C, Williams PL, Whitford GM, Joshipura KJ, Hoover RN, Douglass CW. 2011. An assessment of bone fluoride and osteosarcoma. J Dent Res 90(10):1171-6.

Leite GAS, Sawan RMM, Teofilo JM, Porto IM, Sousa FB, Gerlach RF. 2011. Exposure to lead exacerbates dental fluorosis. Arch Oral Biol 56(7):695-702.

Lupo M, Afonso M, Buzalaf R, Rigalli A. 2011. Effect of fluoridated water on plasma insulin levels and glucose homeostasis in rats with renal deficiency. Biol Trace Elem Res 140:198-207.

Masters RD, Coplan MJ, Hone BT, Dykes JE. 2000. Association of silicofluoride treated water with elevated blood lead. Neurotoxicology 21(6):1091-100.

NRC (National Research Council). 2006. Fluoride in drinking water: a scientific review of EPA’s standards. National Academies Press: Washington, DC. 507 pp.

Poureslami HR, Khazaeli P. Fluoride intake and urinary excretion in preschool children residing in Koohbanan, Iran, a city with high fluoride water and food. Fluoride 43(1):67-70.

Poureslami HR, Horri A, Garrusi B. 2011. A comparative study of the IQ of children age 7-9 in a high and a low fluoride water city in Iran. Fluoride 44(3):163-7.

Reddy PY, Reddy KP, Kumar KP. 2011. Neurodegenerative changes in different regions of brain, spinal cord and sciatic nerve of rats treated with sodium fluoride. J Med Allied Sci 1(1):30-5.

Shivaprakash PK. 2011. Relation between dental fluorosis and intelligence quotient in school children of Bagalkot district. J Ind Soc Pedod Prevent Dent 29(2):117-20.

Spittle B. 2011. Neurotoxic effects of fluoride. Fluoride 44(3):117-124.

Valdez-Jiménez L, Soria Fregozo C, Miranda Beltrán ML, et al. 2011. Effects of the fluoride on the central nervous system. Neurología 26(5):297-300.

Willems HME, van den Heuvel EGHM, Castelein S, et al. 2011. Fluoride inhibits the response of bone cells to mechanical loading. Odontology 99:112-118.

Yang S, Wang Z, Farquharson C, Alkasir R, Zahra M, Ren G, Han B. 2011. Sodium fluoride induces apoptosis and alters bcl-2 family protein expression in MC3T3-E1 osteoblastic cells. Biochem Biophys Res Comm 410(4):910-5.

Zhu W, Zhang J, Zhang Z. 2011. Effects of fluoride on synaptic membrane fluidity and PSD-95 expression level in rat hippocampus. Biol Trace Elem Res 139:197-203.