Another hot topic in the natural health community is fluoride. As you probably know, some countries, including the U.S., Australia, and Canada, add a small amount of fluoride to the public water supply. In the U.S., this practice began in 1945 after scientists noticed that people living in areas with more natural fluoride in the ground water had fewer cavities. In 1962, the practice of adding fluoride to city water supplies became widespread. Some European countries followed suit by fluoridating their water, milk or salt supplies.
Today, this practice is highly controversial among the public. Much of the scientific community cites research showing that fluoride decreases tooth decay. Skeptics claim that fluoride causes a myriad of health problems ranging from weak bones to cancer to impaired brain development. We’ll look more into all of these claims in more depth later.
What is fluoride exactly? Fluorides are compounds that combine the element fluorine with another substance, usually a metal. The types of fluoride added to different water systems include fluorosilicic acid, sodium fluorosilicate, and sodium fluoride.
Fluoride is often found naturally in water, soil, and even air. The amount of fluoride found in ground water can range from 0 to more than 13 parts per million (ppm) (which is the same as saying 13 milligrams per liter (mg/L)). Higher amounts are usually found in rural areas of developing nations including India and China.
Here in the U.S., as in most other developed nations who purposefully add fluoride to their drinking water, the level is around 0.7ppm.
How does fluoride work? It is widely accepted that applying fluoride topically and then spitting it out can help reduce tooth decay by helping the tooth enamel re-mineralize and by impairing bacteria’s ability to eat away at the enamel. The mechanism by which ingested fluoride works is somewhat controversial, but dentists say it works in 2 ways. The first way is by adding fluoride to the inside of children’s teeth while they are forming. The second way is by keeping a very low amount of fluoride in the saliva at all times which can act on the tooth enamel topically.
Adding fluoride to the public water system can cause a variety of serious health problems.
Initial Google Search
Organizations claiming fluoridation is harmful:
First, let’s take a look at what the opposition has to say. Some prominent agencies and personalities that claim fluoride is a threat to public health include: Global Healing Center, Fluoride Action Network, The Center for Natural Dentistry, Dr. Mercola, and Dr. Axe.
First, they say fluoride weakens skeletal health. They claim that the liver cannot process fluoride so it remains in the bloodstream, leeches calcium from bones and causes a condition called skeletal fluorosis. Babies and children excrete less fluoride from their kidneys and absorb up to 80% of ingested fluoride into their bones. Children in fluoridated communities have twice as many bone defects as children who are not. Fluoride also increases hip fractures in the elderly.
Second, they say it causes osteoarthritis by calcifying bone cartilage.
Next, they claim fluoride is toxic to thyroid and pineal gland. The thyroid can absorb fluoride which inhibits its function. Lowered thyroid function has been found in otherwise healthy people at 2.3 ppm. Fluoride was used in the 1800s to reduce thyroid function in people with overactive thyroid. The pineal gland regulates body rhythms and sleep-wake cycles. Fluoride accumulates here and calcifies the gland reducing its function over time.
They claim harm to reproductive health. Fluoride accelerates female puberty due to damage in the pineal gland. Higher levels of fluoridated water consumption correlate to lower fertility rates. Fluoride at high doses damages sperm. Men living in highly fluoridated areas have lower levels of testosterone.
Another claim is reduced kidney health. Higher rates of chronic kidney disease have been reported in areas where water contains high levels of fluoride.
They state that Fluoride causes inflammation and atherosclerosis (heart disease)
They cite negative cognitive effects. Fluoride impairs brain development. Children living in areas with higher amounts of fluoride in the water are 5 times more likely to have low IQ compared to those that do not. Studies show reduced IQ at fluoride levels as low as 0.3ppm (most public water supplies use 1ppm fluoride). Studies also show an association between fluoride exposure and visual-spatial organization. The Environmental Protection Agency (EPA) lists fluoride as one of about 100 chemicals for which there is substantial evidence for developmental neurotoxicity. Animal experiments show that fluoride damages the brain and causes learning and behavior problems. They say these experiments were done with fluoride levels that mimic the public water supply, not at very high doses.
Finally, they claim exposure to higher levels of fluoride in drinking water is linked to higher rates of osteosarcoma in boys.
These were the top health concerns I found in a brief internet search. Additional concerns also exist such as decreased freedom (being forced to drink water with fluoride), a concern that fluoride is an industrial waste product being disposed of in the water, and the belief that its safe use in rat poison allowed it to dodge FDA restrictions.
Organizations claiming fluoridation is safe and beneficial:
Now, let’s take a closer look at why some public agencies (including the American Academy of Pediatrics (AAP), American Dental Association (ADA), Centers for Disease Control and Prevention (CDC), US Public Health Service, and National Research Council) think adding fluoride to the water is beneficial and how they attempt to refute the opposition.
These agencies maintain that fluoride is good for teeth and prevents tooth decay. They say there is no scientifically valid evidence to show that it causes any serious health problems.
They do admit one possible problem resulting from too much fluoride. This is a cosmetic condition known as dental fluorosis which causes discolored patches on teeth. It occurs when young children consume too much fluoride over an extended period of time while their teeth are still growing. They state that fluoride in the U.S. water supply does not typically cause fluorosis because levels are not high enough. Fluoridated water is safe for babies and children, but there is a risk of mild fluorosis if mixing fluoridated water with infant formula or if children frequently swallow fluoridated toothpaste.
Some other arguments they make include:
The fluoride added to drinking water is regulated for safety by the Environmental Protection Agency (EPA) and it is not a by-product of the fertilizer industry.
American IQ scores have risen alongside water fluoridation. A report suggesting fluoride could impair brain development was a review of older studies that included IQ scores of children in China, Mongolia, and Iran. The study did not test cause and effect. The water in these regions had natural fluoride which was up to 10 times higher than the levels used in US public water systems.
Comparing fluoridated and non-fluoridated communities shows that fluoride is really effective at preventing tooth decay.
Fluoridated water is safe for plants, animals and fish. Fluoride occurs naturally in many bodies of fresh water and the average fluoride level in ocean water is much higher than in public water systems.
The American Cancer Society does not take an official position, but they state the following: More than 50 population-based studies have looked at the potential link between water fluoride levels and cancer. Most of these have not found a strong link to cancer.
The US Public Health Service states: Optimal fluoridation of drinking water does not pose a detectable cancer risk to humans as evidenced by extensive human epidemiological data available to date.
The National Research Council (NRC) states: “The weight of the evidence from the epidemiological [population-based] studies completed to date does not support the hypothesis of an association between fluoride exposure and increased cancer risk in humans.”
Is there a safe amount of fluoride? When does it become unsafe?
Does fluoride add up from the drinking water, toothpaste, mouthwash, etc?
Is it better or worse to get fluoride from one source or another? (water v. toothpaste)?
Peer Reviewed Research
For this article, I conducted 10 different searches. The first one was a more generalized search of meta-analyses. These included mostly population studies to show how fluoride has affected large groups of people over time. Then, I went back and searched for evidence linking fluoridation to each adverse health claim cited by opponents. As usual, I’ve included the titles and links to all the research with brief synopses of each. You can read them or simply skip to the next section by clicking here.
Search 1: search term “fluoride”, literature reviews and meta-analyses published within the last 5 years, citing research done on humans.
1. Fluoride in drinking water and diet: the causative factor of chronic kidney diseases in the North Central Province of Sri Lanka. https://www.ncbi.nlm.nih.gov/pubmed/25916575 (2015)
This literature review provides good evidence that naturally occurring fluoride in Sri Lanka has caused chronic kidney disease. The fluoride levels in the water here are known to be excessive. People develop kidney disease over time by drinking the water and eating food made from the ground water.
2. Fluoride toothpastes and fluoride mouthrinses for home use. https://www.ncbi.nlm.nih.gov/pubmed/24308396 (2013)
Fluoride toothpastes and mouthrinses have been developed and extensive testing has demonstrated that they are effective and their use should be encouraged. Concentrations of fluoride (F), commonly found, are 1500 ppm for toothpastes and 225 ppm for mouthrinse. Several systematic reviews have concluded that fluoride-containing toothpastes and mouthrinses are effective, and that there is added benefit from their use with other fluoride delivery methods such as water fluoridation.
3.Water fluoridation and oral health. https://www.ncbi.nlm.nih.gov/pubmed/24308393 (2013)
Millions of people consume fluoridated water. Fluoride can help reduce the number of cavities and re-mineralize tooth enamel. A large number of studies conducted worldwide demonstrate the effectiveness of water fluoridation. Systematic reviews of the safety and efficacy of water fluoridation attest to its safety and efficacy; dental fluorosis identified as the only adverse outcome.
4.Milk fluoridation for the prevention of dental caries. https://www.ncbi.nlm.nih.gov/pubmed/24308395 (2013)
This lit review evaluates several RCTs and other controlled studies and shows that milk fluoridation is also an effective way to prevent cavities, especially in children with school milk programs.
5. Fluoride use in caries prevention in the primary care setting. https://www.ncbi.nlm.nih.gov/pubmed/25157014 (2014)
This review goes over the evidence showing that fluoride decreases dental caries and encourages pediatricians to use fluoride treatments in the primary care setting. It also discusses the possibility of enamel fluorosis if fluoride levels are too high.
6. Salt fluoridation and oral health. https://www.ncbi.nlm.nih.gov/pubmed/24308394 (2013)
This review shows that salt fluoridation is also effective in preventing dental caries and has been successfully implemented in parts of Europe and Latin America.
7.Exposure to fluoride in drinking water and hip fracture risk: a meta-analysis of observational studies. https://www.ncbi.nlm.nih.gov/pubmed/26020536 (2015)
Fourteen observational studies involving thirteen cohort studies and one case-control study were included in this meta-analysis. Researchers found that exposure to fluoride in drinking water does not significantly increase the incidence of hip fracture.
8. Focus on fluorides: update on the use of fluoride for the prevention of dental caries. https://www.ncbi.nlm.nih.gov/pubmed/24929594 (2014)
This review reiterates the effectiveness of water fluoridation and fluoride treatments. However, it also discusses new recommendations to reduce the amount of fluoride children are exposed to as not to cause dental fluorosis.
9. Water fluoridation: a critical review of the physiological effects of ingested fluoride as a public health intervention. https://www.ncbi.nlm.nih.gov/pubmed/24719570 (2014)
This article states that water fluoridation is controversial because it has the potential to cause major health problems while only having a modest dental caries prevention effect. The author notes that fluoride is a waste product of aluminum, fertilizer and iron ore manufacture and should not be discharged into the environment. The author argues that “systemic fluoride ingestion” should not be used to improve dental health.
10. Does cessation of community water fluoridation lead to an increase in tooth decay? A systematic review of published studies. https://www.ncbi.nlm.nih.gov/pubmed/27177581 (2016)
This review found 15 instances of communities that once had fluoridated water, but then stopped their programs. The authors state results were somewhat mixed, but overall, people got fewer cavities during the time period when the water was fluoridated.
Search 2: search terms “fluoride” and “skeletal fluorosis”, any relevant studies published within the last 5 years using human subjects
11. A brief review on experimental fluorosis. (2013) https://www.ncbi.nlm.nih.gov/pubmed/24050947
This entire abstract is worth reading. The article reviews many harmful effects that can occur from consuming too much fluoride. I did not have access to full text.
Fluoride (F) is a naturally occurring contaminant in the water. F is essential for normal maintenance of teeth and bones. However, prolonged exposure to high concentration of F is found to be deleterious to teeth, bones and other organs. Besides drinking water, F can enter the body through food, dental products, drugs and industrial emission. People living in areas where F contamination is much higher than the expected level, are found to suffer from not only teeth and bone problem but also other systems, including brain and its functions. Since animals respond to the toxic effects of F like human beings, the deleterious effects of F have been produced experimentally in animals in order to determine the mechanism involved in the action of F. The reports indicating the chronic harmful effects of F in teeth, bones, heart, liver, kidneys, gastrointestinal tract, lungs, brain, blood, hormones and biochemical parameters of experimental animals and in in vitro studies have been reviewed in this article. The neurotoxic action of F that produces chiefly learning and memory impairment has also been included. The review also points out the harmful effects of F on reproduction, its teratogenic action and in inducing premature ageing. Finally, the reports indicating a reversal of certain toxicities of F in experimental animals after withdrawal of its exposure has been included.
12. Modifying Role of GSTP1 Polymorphism on the Association between Tea Fluoride Exposure and the Brick-Tea Type Fluorosis. (2015) https://www.ncbi.nlm.nih.gov/pubmed/26046522
Brick tea type (skeletal) fluorosis is a public health concern in the north-west area of China. This tea is made from tea leaves which retain most of the fluoride present in the surrounding air and soil. This problem is not due to public water fluoridation or dental treatments. Researchers found that genes may play a role in the severity of fluorosis one develops from drinking this tea.
13. Association of Temporomandibular Joint Signs & Symptoms with Dental Fluorosis & Skeletal Manifestations in Endemic Fluoride Areas of Dungarpur District, Rajasthan, India. (2015) https://www.ncbi.nlm.nih.gov/pubmed/26816986
Endemic fluorosis resulting from high fluoride concentration in groundwater is a major public health problem. India is among the numerous nations, where fluoride sullied groundwater is creating wellbeing issues. This study found that TMJ was also associated with dental and skeletal fluorosis in India.
14. Prevalence of skeletal fluorosis in fisherman from Kutch coast, Gujarat, India. (2015) https://www.ncbi.nlm.nih.gov/pubmed/26656421
In health terms, consuming fluoride is well recognized to be a double-edged sword. Consumption of optimal amounts is beneficial to health, however an excess constitutes a health hazard. This study found that 30% of fisherman in Kutch coast, Gujarat, India had some degree of skeletal fluorosis due to fluoride concentrations in the drinking water. The drinking water in this area was between 3.4 and 6.9 ppm.
15. Dietary Fluoride Intake and Associated Skeletal and Dental Fluorosis in School Age Children in Rural Ethiopian Rift Valley. (2016) https://www.ncbi.nlm.nih.gov/pubmed/27472351
This study showed that children in a part of rural Ethiopia had dental and skeletal fluorosis from drinking ground water and eating food cultivated with this water. Children here were regularly consuming more than 10 mg of fluoride per day (much more than the highest acceptable dose in the US). The research also found that higher consumption of calcium and using rain water rather than ground water could reduce fluorosis in this region.
16. Study of the relationship between the lifestyle of residents residing in fluorosis endemic areas and adult skeletal fluorosis. (2015) https://www.ncbi.nlm.nih.gov/pubmed/26183810
Excerpt from abstract:
The relationship between fluorosis and the lifestyle of adult residents of areas in which fluorosis is endemic was evaluated. Our results showed that protective factors against skeletal fluorosis included drinking boiled water, storing water in a ceramic tank, and ingesting fruits, vitamin A, thiamine, and folic acid. Risk factors for skeletal fluorosis were overweight status and obesity, drinking tea, drinking water without storage, and ingestion of oils, fats, and phosphorus.
Search 3: search terms “fluoride” and “osteoarthririts”, any relevant studies published within the last 5 years using human subjects
I found no research linking fluoridated drinking water, food, beverages or dental products to osteoarthritis. A search of “fluoride” + “osteoarthritis” yielded results showing that a certain type of PET scan (18F-fluoride PET) can be used to evaluate hip osteoarthritis. These studies are irrelevant to our questions because they do not involve consumption of fluoride in the daily diet.
Search 4: search terms “fluoride” and “thyroid”, any relevant studies published within the last 5 years using human subjects
17. The effects and underlying mechanism of excessive iodide on excessive fluoride-induced thyroid cytotoxicity. (2014) https://www.ncbi.nlm.nih.gov/pubmed/25104093
This study found that excessive amounts of fluoride can damage human thyroid cells. It also found that excessive iodide is often found with excessive fluoride. This can cause further thyroid damage. I did not determine exactly how much they considered to be “excessive”, but this study does seem to be referring to excessive fluoride and iodide in ground water and not public water systems in which fluoride has been added.
18. Public perceptions and scientific evidence for perceived harms/risks of community water fluoridation: An examination of online comments pertaining to fluoridation cessation in Calgary in 2011. (2015) https://www.ncbi.nlm.nih.gov/pubmed/26680434
This study looked at public concerns about fluoridation. It found that people are concerned about the effect of fluoride on their health, the environment, and animal health. However, evidence people cited was weak and typically included anecdotes and what they considered to be expert opinions. The authors stated that when they searched the literature, they did find evidence of harm to the thyroid and to phytoplankton at levels exceeding 1.5 ppm (the current recommendation is 0.7ppm).
19. Fluoride exposure and indicators of thyroid functioning in the Canadian population: implications for community water fluoridation. (2017) https://www.ncbi.nlm.nih.gov/pubmed/28839078
This study analyzed data from a large population in Canada that gets fluoridated water. They found no association between fluoride (from community water systems and toothpaste/mouthwash) and thyroid dysfunction or abnormal levels of thyroid stimulating hormone.
20. Dental fluorosis, nutritional status, kidney damage, and thyroid function along with bone metabolic indicators in school-going children living in fluoride-affected hilly areas of Doda district, Jammu and Kashmir, India. (2017) https://www.ncbi.nlm.nih.gov/pubmed/29063198
This study included 824 children age 8-15. Half were from an area with high levels of fluoride in the ground water and half were not. In children from the high fluoride area, they found fluorosis, chronic kidney damage and decreased thyroid stimulating hormone. I was unable to determine exactly how much fluoride was in the water in the high-fluoride area.
Search 5: search terms “fluoride” and “pineal gland”, any relevant studies published within the last 10 years using human subjects
21. Fluoride deposition in the aged human pineal gland. (2001) https://www.ncbi.nlm.nih.gov/pubmed/11275672
The purpose of this study was to discover whether fluoride accumulates in the aged human pineal gland. Cadaver studies were performed. They found that by old age, the pineal gland has readily accumulated fluoride and its fluoride to calcium ratio is higher than bone.
Search 6: search terms “fluoride” and “puberty”, any relevant studies published within the last 10 years using human subjects
No studies found investigating whether fluoride causes early puberty.
Search 7: search terms “fluoride” and “fertility”, any relevant studies published within the last 5 years using animal subjects (no relevant studies on human subjects found)
22. The toxicity mechanism of sodium fluoride on fertility in female rats. (2013) https://www.ncbi.nlm.nih.gov/pubmed/24071475
This study showed that high levels of fluoride in drinking water (100-200mg/liter) caused reductions in reproductive hormones and problems with related receptor proteins in female rats. (keep in mind, the recommended amount of fluoride in public drinking water is 0.7mg/liter).
23. Effect of sodium fluoride on male mouse fertility. (2015) https://www.ncbi.nlm.nih.gov/pubmed/25854509
This study found that high concentrations of sodium fluoride could impair mouse sperm’s motility and ability to fertilize an egg in vitro (outside the body).
24. Sodium fluoride activates ERK and JNK via induction of oxidative stress to promote apoptosis and impairs ovarian function in rats. (2014) https://www.ncbi.nlm.nih.gov/pubmed/24681588
This study also tested female rats who had received 100-200 mg/liter of fluoride in their drinking water. They found that the fluoride caused ovarian cell death caused by oxidative stress.
25. Toxic effects of sodium fluoride on cell proliferation and apoptosis of Leydig cells from young mice. (2014) https://www.ncbi.nlm.nih.gov/pubmed/25074826
This study found similar results to the one above, but went into more detail about the mechanisms of cell death caused by high levels of fluoride.
26. Adverse Effects of High Concentrations of Fluoride on Characteristics of the Ovary and Mature Oocyte of Mouse. (2015) https://www.ncbi.nlm.nih.gov/pubmed/26053026
This study found similar results to the studies above.
27. Effects of sodium fluoride on reproductive function in female rats. (2013) https://www.ncbi.nlm.nih.gov/pubmed/23459146
Again, this study also found reduced fertility in female rats that had been exposed to high levels of fluoride. They also found that it damaged the structure of the uterus.
Search 8: search terms “fluoride” and “IQ”, any relevant studies published within the last 5 years using human subjects
28. A cross-sectional study to assess the intelligence quotient (IQ) of school going children aged 10-12 years in villages of Mysore district, India with different fluoride levels. (2015) https://www.ncbi.nlm.nih.gov/pubmed/26381633
This study found that children in India whose water contained high levels (2.2mg/liter) of fluoride had lower IQs than children who drank water with less fluoride (1.2mg/liter or less).
29. Dental fluorosis and urinary fluoride concentration as a reflection of fluoride exposure and its impact on IQ level and BMI of children of Laxmisagar, Simlapal Block of Bankura District, W.B., India. (2015) https://www.ncbi.nlm.nih.gov/pubmed/26960765
This study found that dental fluorosis and urinary fluoride was negatively associated with IQ in children in India whose drinking water had approximately 2.11 mg/liter of fluoride.
30. Inferring the fluoride hydrogeochemistry and effect of consuming fluoride-contaminated drinking water on human health in some endemic areas of Birbhum district, West Bengal. (2016) https://www.ncbi.nlm.nih.gov/pubmed/26164468
This study found correlations between children with fluorosis and lower IQs in West Bengal. The amount of fluoride in drinking water in this area varies from 0.33 to 18.08 mg/liter.
31. Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6-12 Years of Age in Mexico. (2017) https://www.ncbi.nlm.nih.gov/pubmed/28937959
This study found that high prenatal fluoride exposure was associated with lower scores on IQ tests in children at ages 4-12. I was unable to determine the amount of fluoride in the water that was considered “high” in this study.
32. Fluoride exposure and reported learning disability diagnosis among Canadian children: Implications for community water fluoridation. (2017) https://www.ncbi.nlm.nih.gov/pubmed/28910243
This study found no link between fluoride exposure and lower IQ or other cognitive diagnoses in children in Canada. Researchers here, like in other studies, used urinary fluoride to determine levels of fluoride consumption. However, they also used “creatine-adjusted urinary fluoride” which the authors stated provides a more accurate measurement. I was unable to determine the exact amounts of fluoride in the Canadian drinking water.
Search 9: Search terms “fluoride” and “osteosarcoma” (bone cancer), any relevant studies published within the last 5 years using human subjects
33. Is fluoride a risk factor for bone cancer? Small area analysis of osteosarcoma and Ewing sarcoma diagnosed among 0-49-year-olds in Great Britain, 1980-2005. (2014) https://www.ncbi.nlm.nih.gov/pubmed/24425828
This study examined 2,566 cases of bone cancer in Great Britain. Researchers found no association between higher levels of fluoride in the water and bone cancer.
34. Fluoride exposure in public drinking water and childhood and adolescent osteosarcoma in Texas. (2016) https://www.ncbi.nlm.nih.gov/pubmed/27189068
This study looked at 308 cases of osteosarcoma in children and adolescents in Texas between 1996 and 2006. They also had a control group of children diagnosed with leukemia or CNS tumors. Researchers found no association between fluoride levels in public drinking water and bone cancer.
35. Community water fluoridation and health outcomes in England: a cross-sectional study. (2015) https://www.ncbi.nlm.nih.gov/pubmed/26153549
This study looked for associations between fluoride and a number of health outcomes in areas in England with public water fluoridation. They found strong evidence that fluoridated water reduces dental caries in children. There was no evidence of an association between fluoride and hip fracture, Down syndrome, all-cancer, all-cause mortality or osteosarcoma. Bladder cancer and renal stones were negatively associated with fluoridation.
Search 10: Search terms “fluoride” and “heart disease”, any relevant studies published within the last 5 years using human subjects
36. Natural fluoride in drinking water and myocardial infarction: A cohort study in Sweden. (2016) https://www.ncbi.nlm.nih.gov/pubmed/27100011
This study looked at 455,619 individuals born in Sweden between 1900 and 1919. They were divided into groups based on the amount of fluoride in their drinking water. Groups ranged from <0.3 mg/liter to >1.5mg/liter. Myocardial infarction (heart attack) was not associated with water fluoride levels for any of the groups.
What We Know and Don’t Know
From on my search of meta-analysis and literature reviews, 7 out of 8 articles supported water, salt, or milk fluoridation. Thousands of people were studied over time and people who ingested small amounts of fluoride had about 50% fewer cavities than those who did not. However, the rate of cavity reduction varied throughout the literature from 15-60%.
The only adverse health effect seen in these studies was dental fluorosis in young children. Some of the studies recommended reducing overall fluoride for children by using non-fluoridated water in infant formula or by using non-fluoridated toothpastes for very young children who may swallow it.
One review stood out from the others by claiming fluoridated water is more harmful than beneficial. The authors cite evidence that topical fluoride is effective in reducing cavities, but ingested fluoride is not. They cite research questioning the safety of moderate doses of fluoride and show how fluoride consumption can add up easily depending on what/how much a person eats or drinks.
In my first search, I also came across one meta-analysis that looked at hip fractures. It found that hip fractures were not linked to fluoridated water. Another meta-analysis looked at kidney disease in an area with very high levels of ground water fluoride. This study found a clear link between fluoride and kidney disease.
The second search I did focused on skeletal fluorosis, which is a painful condition caused by fluoride accumulating in the bones and joints. I found 6 relevant articles, all of which confirmed that too much fluoride causes skeletal fluorosis. These studies were done in developing nations with ground fluoride levels around 3-7ppm. They also discovered some genetic predisposition to fluorosis.
The third search yielded no results linking fluoride to osteoarthritis.
Search 4 evaluated the effects of fluoride on the thyroid. Across studies, thyroid damage was found in areas of high fluoride ground water, but not in areas that added small amounts of fluoride to drinking water.
Search 5 confirmed that fluoride does accumulate in the pineal gland over time. No adverse effects were discussed in the cadaver study article I found. No other research was found linking fluoride consumption to pineal gland damage.
Search 6 yielded no results linking fluoride consumption to early puberty.
In search 7, I found a wealth of literature linking high levels of fluoride to fertility problems in mice. However, the mice studied consumed about 100-200 times recommended the amount of fluoride. Fertility problems were consistently found in both male and female mice.
Search 8 evaluated the link between fluoride and child IQ. Again, I found several studies correlating high levels of fluoride in ground water in developing countries to lower IQ. Levels of fluoride in these studies varied widely (up to 18 times the recommended amount).
For search 9, I found 3 robust studies looking at community water fluoridation and rates of osteosarcoma. No study found any associations. These studies were done in developed countries who purposefully fluoridated their water supply.
Finally, search 10 evaluated a link between fluoride and heart attack. I found one study which was from Sweden. No link was found.
To summarize, here is what we know:
Many developing countries drink well water that has fluoride concentrations 2-18 times the recommended concentration. There are well-established health risks to consuming these larger amounts of fluoride. These include skeletal fluorosis, kidney disease, thyroid damage, impaired brain development, and possibly decreased fertility.
Other countries drink water containing around 0.7ppm fluoride. This amount of fluoride is strongly correlated with reduced dental caries, especially in children. Fluoride works in 2 ways to reduce cavities. First, it works by strengthening teeth from the inside while they are forming. Second, it works by helping to reduce bacteria and improve the rebuilding of enamel when applied topically.
At fluoride concentrations between 1-2 ppm, some children will develop dental fluorosis, or discoloration of teeth. This is the first sign that a child may be receiving too much fluoride. This can also happen if a child regularly swallows toothpaste or mouthwash.
To answer my follow-up questions, yes there is a point where fluoride levels go from beneficial to detrimental. It seems like the greatest benefits are between 0.7 and 1.0ppm while mild adverse effects start to occur around 2ppm. Fluoride does add up from all sources. Dentists recommend both ingested and topical sources, but we should keep in mind that these add up. This is the main reason community water supplies were reduced from 1 to 0.7ppm. I was unable to find data regarding whether ingested or topical fluoride is safer or more effective. One thing to consider is that ingested fluoride actually acts topically by simply being present in saliva.
Conclusions and Applications
Based on my research, community water fluoridation is safe. It prevents about a quarter to half of dental caries in the general population. People who drink well water, especially in developing nations, are at risk for several serious health problems. People who drink from the public water supply in the U.S. are not.
My recommendation is not to worry about the fluoride in your water. If you are concerned about your children developing dental fluorosis, consider limiting their exposure. Make sure they don’t swallow fluoride toothpaste and consider alternating fluoridated and non-fluoridated water sources.