The New Science of Fluoride
A Case of Strange Loves and Misguided Hates
That’s the common sentiment when attempting to engage listeners or readers with the issue of water fluoridation. Thus, the quick jump to comical Dr. Strangelove analogies, subversive Communist plots, or in the case of the February 23, 2015 New York Times article, interesting historical details about “New York’s Fluoridation Fuss”, the city’s 50 year practice of treating tooth decay via its public water supply.
One of our country’s brightest physicists, Richard Feynman, said about science, “We’ve learned from experience that the truth will come out.” And in fact, with regards to fluoride, the truth is coming out. But given entrenched dogma, industry interests, and bureaucratic inertia, this truth is certainly not yet sinking in. Those who, based on recent science, advocate for the reexamination of drinking fluoride are routinely dismissed and ridiculed. This is a somewhat unexpected sentiment given our burgeoning interest in the intersection between accumulating numbers of environmental toxins and ballooning rates of chronic diseases. Can we afford to overlook the one toxin that two-thirds of Americans drink everyday?
The new science of fluoride comes from the EPA, Harvard Researchers, and the National Research Council, and looks like this:
1. Fluoride is a developmental neurotoxin.1 2 A developmental neurotoxin is a chemical that can negatively affect nerve cells during brain development in utero, in babies and in children. Toxic insults during brain development manifest as neurodevelopmental diseases such as Autism Spectrum Disorders, learning difficulties, ADHD, and cognitive-behavorial issues. The EPA recently placed fluoride on its list of developmental neurotoxins with substantial evidence for neurotoxicity.3 Subsequently, researchers at the Harvard School of Public Health, after years of studying
the neurotoxic effects chemicals such as lead and mercury, added fluoride to their burgeoning list of clinically important developmental neurotoxins. They noted that “Fluoride seems to fit in with lead, mercury, and other poisons that cause chemical brain drain. The effect of each toxicant may seem small, but the combined damage on a population scale can be serious, especially because the brain power of the next generation is crucial to all of us.” 4
2. The CDC reports that 58% of African American children and 36% of white children have dental fluorosis — a white speckling of one’s permanent teeth that indicates an overexposure to fluoride between conception and age 8.5 6 New data, again out of the Harvard School of Public Health, shows a statistically significant correlation between mild, moderate and severe dental fluorosis and reduced memory scores on the WISC-IV digit span IQ subtest in children.7 This measurable loss of IQ often goes in hand with more noticeable impairments in brain functioning, such as ADHD, learning disabilities, and behavioral disorders. Because of now-widespread water fluoridation, the heavy use of fluoride-based pesticides, fluoridated toothpastes, and juices, foods, and sodas made with fluoridated water, our fluoride exposure has increased significantly in the last 25 years, as evidenced by this rapidly rising rate of dental fluorosis, which has doubled in a 20 year period. Overexposing our children to a developmental neurotoxin is questionable public health policy.
3. Fluoride is an endocrine disruptor. It has the ability to suppress thyroid hormone production, and in fact was used in the 1950s as a medication to treat an overactive thyroid gland. The 2006 National Research Council’s scientific review of EPA’s standards, reported that ingesting .05 mg/kg/day of fluoride (or as low as .03 mg/kg/day in a person with inadequate iodine intake), decreases one’s production of thyroid hormone.8 That is, as little as 1.6 to 2.7 liters of fluoridated tap water a day can impair thyroid hormone production in a 120 pound female. That’s four 8 oz. glasses of water, one beer (most are made with fluoridated tap water), a bowl of homemade soup, and one 16 oz. bottled juice or soda. And this does not take into account additional fluoride exposures that we all get from fluoridated toothpastes, dental varnish, or fluoride-based pesticides on inorganic fruits and vegetables. Another study raising concern about fluoride and the thyroid gland is in this month’s British Medical Association Journal of Epidemiology and Community Health. The study found that fluoride in a community’s drinking water is a predictor of higher rates — 30% higher — of hypothyroidism in that community.9
4. While we used to think fluoride was incorporated into developing teeth to make them strong and cavity-resistant, the CDC now says science shows this to be incorrect. The MMWR, or Morbidity and Mortality Weekly Report, also known as the “voice of the CDC”, reported that “laboratory and epidemiologic research that has led to the better understanding of how fluoride prevents dental caries, indicates that fluoride’s predominate effect is post eruptive and topical”.10 Thus, recent science tells us that we do not need to ingest fluoride to get its cavity-fighting effects. In this time of precision medicine, does it make sense to administer a medical treatment systemically, when it is safest and most effective when delivered topically?
5. The CDC’s recommended safe amount of fluoride for in utero babies and infants up to 6 months is .01 mg per day, a minuscule amount. The CDC’s “tolerable upper intake” or level above which negative health impacts occur, is .7 mg per day for a 6 mont old infant.11 Infants fed formula made with fluoridated tap water receive just over 1 mg a day of fluoride, a dose that, according to the National Research Council data, can decrease the production of thyroid hormone. The unfortunate irony here is that infants don’t yet have teeth on which the fluoride can act. The risk benefit ratio of water fluoridation is frighteningly backwards.
6. Water fluoridation is often cited as a particularly equitable way of delivering medical treatment, since it reaches people without regard to color or socioeconomic status. But, according to officials at the Department of Health and Human Services, “blacks have higher levels of dental fluorosis than whites (58% vs. 36%) based on 1999-2004 NHANES data.” 12 Additionally they note that “No clear explanation exists why fluorosis was more severe among non-Hispanic black children than among non-Hispanic white or Mexican-American children. This observation has been reported elsewhere, and different hypotheses have been proposed, including biologic susceptibility or greater fluoride intake.”13 The data is so alarming that Andrew Young, the former mayor of Atlanta and U.S. Ambassador to the U.N., has called for the repeal of Georgia’s mandatory community water fluoridation laws. Disproportionately overexposing minority populations to a neurotoxin is not equitable health policy.
“Science is organized common sense where many a beautiful theory was killed by an ugly fact.” —Thomas Huxley
Why is the recent science of fluoride so hard to swallow? Is it simply too distasteful to accept the ugly fact that fluoride is not the shiny silver bullet we’d hoped, but also toxically targets our brains and thyroid glands? Is questioning “one of the greatest health achievements of the 20th century” too consternate a task? Does accepting the science mean parents of children with dental fluorosis must wonder if something as innocent as tap water played a part in their child’s ongoing learning difficulties? Does believing the science mean being on par with Dr. Strangelove’s ridiculed rogue general, Jack. D. Ripper?
Whatever our hesitancy, we have no choice but to swallow the bitter pill of fluoride science and reexamination our practice of water fluoridation. Right now in our country one in six children suffers from a neurodevelopmental brain disease, a group of illnesses whose incidence continues to rise each year. A group of disorders that stem from insults during the crucial period from conception to age 15 of rapid and intricate brain development.
In our country one in eight women will develop thyroid disease in their lifetime; that is one in eight women with hypothyroidism, hyperthyroidism, Hashimoto’s thyroiditis, thyroid cancer, or Grave’s Disease.
The increasing incidence of these two disease groups is driven by accumulating numbers of environmental toxins. We know that fluoride is but one of many developmental neurotoxins and endocrine disruptors currently in play as potential culprits of these epidemics, but our rapidly rising rate of dental fluorosis indicates that fluoride, and our overexposure to it, is a key figure in the game.
Water fluoridation dates back to a time when feet were x-rayed to determine shoe size, Valium was good for housewives, and above-ground nuclear testing was exciting to watch. Water fluoridation began before the fields of molecular toxicology or molecular genetics existed, and before we had an appreciation for the complexities and nuances of our endocrine system, the insidious nature of toxins, and our intricate brain biology. Recent science has handed us new and disturbing truths. We are imprecisely dosing our children with a drug that, at best, reduces the number of fillings by 25%.14 Thus, we are risking developmental neurotoxicity and thyroid gland dysfunction, for three instead of four cavities. For the sake of our children and our children’s children, the disturbing truth must trump the comfort of entrenched dogma. Dr. Strangelove’s General Jack D. Ripper may have believed in communist plots, and drunk only distilled water, but our disillusionment with fluoride need not even look that rogue. What more established path is there than science guiding public health policy?
—Angela C. Hind, M.D.
1 Grandjean, P. et al., “Neurobehavioural Effects of Developmental Toxicity,” The Lancet Neurology , Volume 13 , Issue 3 , 330 – 338 (March 2014).
2 Choi, et al., “Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis,” Environmental Health Perspectives, 120(10): 1362-1368 (2012).
3Mundy, W., et al., “Building a Database of Developmental Neurotoxicants: Evidence from Human and Animal Studies,” available at
4News Release, “Impact of Fluoride on Neurological Development in Children,” available at http://www.hsph.harvard.edu/news/features/
5 NHANES data, summarized in correspondence from Nadine Gracia, Office of the Asst. Secretary for Health, HHS, to Dora Hughes, HHS, April 27, 2011.
6 Beltrán-Aguilar E.D., et al., “Surveillance for Dental Caries, Dental Sealants, Tooth Retention, Edentulism, and Enamel Fluorosis-United States, 1988–1994 and 1999-2002” MMWR 54(03);1-44, Table 23 (August 26, 2005).
7Choi, et al., “Association of lifetime exposure to fluoride and cognitive functions in Chinese children: A pilot study,” Neurotoxicology and Teratology 47: 96-101 (January-February 2015).
8National Research Council, Fluoride in Drinking Water A Scientific Review of EPA’s Standards, at 262 (The National Academies Press 2006).
9Peckham S, et al., “Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of
GP practice data and fluoride levels in drinking water,” J. Epidemiol Community Health 0:1–6 (2015).
10 Centers for Disease Control, Morbidity and Mortality Weekly Report (MMWR), “Recommendations for Using Fluoride to Prevent and
Control Dental Caries in the United States” 50(RR14);1-42 (August 17, 2001).
11 Centers for Disease Control, Morbidity and Mortality Weekly Report (MMWR), “Recommendations for Using Fluoride to Prevent and
Control Dental Caries in the United States” 50(RR14);1-42 (August 17, 2001).
12 NHANES data, summarized in correspondence from Nadine Gracia, Office of the Asst. Secretary for Health, HHS, to Dora Hughes, HHS,
April 27, 2011.
13Beltrán-Aguilar E.D., et al., “Surveillance for Dental Caries, Dental Sealants, Tooth Retention, Edentulism, and Enamel Fluorosis-United States, 1988–1994 and 1999-2002” MMWR 54(03);1-44, Table 23 (August 26, 2005).
Water Fluoridation and Our Thyroid
The February 26, 2015 Chicago Tribune article , “British Study Links Fluoride, Underactive Thyroid”, discussed the recent study linking fluoridated water to higher rates of hypothyroidism. The article included comments from the American Dental Association spokesman, Dr. Edmond Hewlett, who claimed that “the 2006 report by the U.S. National Research Council found no adverse effects on the thyroid even at levels more than four times greater than that used in fluoridation.”
In fact, in 2006 the National Research Council found that ingesting .05 mg/ kg/day or more of fluoride depresses levels of thyroid hormone (.03 mg/kg/ day for the 15% of Americans with inadequate iodine intake).1 For a healthy 120-pound female, this is the amount of fluoride in 2. 7 liters of fluoridated water (1.6 liters of fluoridated water if iodine deficient). Considering that fluoridated water not only is drunk from the tap, but also is consumed in all beverages and foods prepared with tap water (sodas, sports drinks, beer, wine, soups, processed foods, etc.), many women in this country receive enough fluoride to affect their thyroid gland’s function. And, we all receive additional fluoride from fluoridated toothpaste, dental varnishes, and fluoride-based pesticides on foods.
One in eight women in our country will develop thyroid disease, including hypothyroidism, thyroid cancer and Grave’s Disease. Thyroid cancer is one of our most rapidly-increasing cancers. We know there is a strong correlation between thyroid disease and exposure to environmental toxins . From the NRC data, we also know that many women are ingesting more than enough fluoride to impact their thyroid function.
For the ADA to state that ”currently, the best available scientific evidence indicates that optimally fluoridated water does not have an adverse effect on the thyroid gland or its function" not only is inaccurate, it disregards the health of the 20 million people in our country living with thyroid disease, as well as those who are yet-undiagnosed. For a dentist to “take issue” with a study showing a significant correlation between fluoridated water and hypothyroidism is medically naive.
While fluoride once was seen as a silver bullet for tooth decay, targeting only the teeth, we now know that its effects on one’s body are far-reaching. In addition to the thyroid gland, fluoride has recently been placed on the EPA’s list of developmental neurotoxins, alongside lead and mercury, as a chemical with the potential to negatively affect an infant’s developing brain.2 3
The recent science of fluoride demands that doctors, as well as dentists, shape the debate about water fluoridation.
--- Angela C. Hind, M.D.
1 National Research Council, Fluoride in Drinking Water A Scientific Review of EPA’s Standards, at 262 (The National Academies Press 2006).
2 Grandjean, P. et al., “Neurobehavioural Effects of Developmental Toxicity,” The Lancet Neurology , Volume 13 , Issue 3 , 330 – 338 (March 2014).
3Mundy, W., et al., “Building a Database of Developmental Neurotoxicants: Evidence from Human and
Animal Studies,” available at http://www.epa.gov/ncct/toxcast/files/summit/48P%20Mundy%20TDAS.pdf (March 2009).