Fluoride

There are some nutrients that get over-hyped, and then there are others that get totally demonized without much scientific evidence. Fluoride is one of those nutrients, so let’s discuss this mineral from an evidence-based perspective. 

Fluoride is the ionic form of the element fluorine. This form is known to stabilize mineralized tissue (i.e., bones and developing teeth). How does this work? Well, the majority of minerals found in teeth are crystals of calcium and phosphate, also called hydroxyapatite. Since fluoride is highly reactive and small in size, it is able to bind the hydroxyapatite and fill empty spaces in the crystal, creating fluoroapatite. Fluoroapatite is known to harden tooth enamel and stabilize bone mineral content – all good things for dental health!

There is one really clear relationship to health and disease here: the prevention of tooth decay. Cavity-causing bacteria in dental plaque create holes in tooth enamel by metabolizing sugars on the teeth to organic acids that dissolve it. We all know that untreated cavities can cause pain, infection, and even tooth loss – but did you know that cavities are also associated with other health conditions? Namely, systemic inflammation seems to explain a relationship between gum infections and insulin resistance, type 2 diabetes, and hypertension. So, maintaining oral health is important for overall health! Topical fluoride works by directly inhibiting demineralization inside the teeth, enhancing remineralization at the crystal surfaces of the teeth, and protecting against bacterial enzymes.Remineralized enamel that includes fluoride is particularly resistant to cariogenic (cavity-causing) bacteria. The action of fluoride is topical – ingestion of it isn’t necessary to see the protective effects. In fact, huge epidemiological studies have shown a reduction between 23-43% in tooth decay in children and teens that use fluoride toothpaste (compared to those who don’t).

[As an aside: it’s important to note here that fluoride isn’t the only show in town when it comes to protecting tooth enamel and preventing cavities. Novamin (or biomin), nano-hydroxyapatite, tricalcium phosphate, arginine (or arginine bicarbonate), and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP, note the dairy protein in this last one) have all been shown to effectively remineralize teeth (sometimes additively, which is cool). Baking soda and xylitol protect against gingivitis and plaque but there’s only limited evidence that they can protect against cavities. Bentonite clay requires more studies (the chemical composition is similar to many proven man-made compounds) and charcoal-based toothpastes (if there isn’t other beneficial ingredients) don’t seem to work. Also note that the microbiome in the mouth and overall diet are the major determinants of dental health.]

Systemic fluoride, on the other hand, does not get incorporated into teeth and saliva in sufficient quantities to exert these effects, at least when consumed in nontoxic doses.

In a nutshell, fluoride is most beneficial when it makes prolonged contact with tooth surfaces rather than building up within the body. If we are using fluoridated toothpaste, drinking non-fluoridated water appears to pose no risk to oral health. Currently, most developed countries (including Japan and the majority of Western Europe) do not fluoridate their water.

Whether fluoridated water is harmful is another topic entirely, and the science here is much less settled. The EPA currently approves fluoride levels in water of up to 4 mg/L, while the Department of Health and Human Services recommends an upper limit of 0.7 mg/L (reduced in 2011 from a range of 0.7 to 1.2 mg/L). A 2015 Cochrane Review found that at fluoride levels of 0.7 mg/L, about 40 percent of the population develops some degree of dental fluorosis, a condition in which excess fluorine compounds cause discoloration and mottling of the teeth.

Because people tend to drink more water (and therefore ingest more fluoride) when the weather is hot, dental fluorosis is more prevalent in warmer regions, even when the fluoride levels in the water are relatively low. Higher levels of fluoride (3 to 6 mg/L) can cause adverse changes in bone structure, and levels above 10 mg/L can cause crippling skeletal fluorosis.

Apart from known problems with fluorosis, much of the safety controversy surrounding water fluoridation stems from inadequate high-quality research. For example, some concerns exist with the type of fluoride used. Whereas the fluoride salts used in dentistry (like sodium fluoride and stannous fluoride) have been widely tested for safety, the silicofluorides added to drinking water (by-products of manufacturing phosphate fertilizers) haven’t been the subject of many toxicology studies. There have been large epidemiological studies demonstrating that fluoridation is not associated increased risk of cancer, heart disease, kidney disease, liver disease, thyroid disease, Alzheimer’s disease, birth defects, or Down’s syndrome. But some studies have uncovered correlations between local water fluoride levels and lower IQ in children, leading to fears that fluoride, which can penetrate the blood-brain barrier in fetuses, negatively impacts early brain development. Fluoride also seems to accumulate in the pineal gland (the gland in our brain that secretes the sleep hormone melatonin) as we age, although the ramifications of this are unknown. Overall, more research is needed to clarify the risks and benefits of water fluoridation for both children and adults.

You can get fluoride from foods, in particular grapes, dried fruit,  cocoa powder, walnuts and tea.

 

Citations

Cerklewski FL. Fluoride bioavailability–nutritional and clinical aspects. Nutr Res. 1997;17:907-929.

Cerklewski FL. Fluorine. In: O’Dell BL, Sunde RA, eds. Handbook of nutritionally essential minerals. New York: Marcel Dekker, Inc; 1997:583-602.

Cerklewski FL. Fluoride–essential or just beneficial. Nutrition. 1998;14(5):475-476.

S Department of Health and Human Services Federal Panel on Community Water Fluoridation. US Public health service recommendation for fluoride concentration in drinking water for the prevention of dental caries. Public Health Reports. Vol 130, 2015. Available at: http://www.publichealthreports.org/documents/PHS_2015_Fluoride_Guidelines.pdf. Accessed 4/29/15.

Centers for Disease Control. Achievements in public health, 1900-1999: fluoridation of drinking water to prevent dental caries. MMWR. 1999;48:933-940.

Demmer RT, Squillaro A, Papapanou PN, et al. Periodontal infection, systemic inflammation, and insulin resistance: results from the continuous National Health and Nutrition Examination Survey (NHANES) 1999-2004. Diabetes Care. 2012;35(11):2235-2242.

Beltrán-Aguilar ED, Barker L, Dye BA. Prevalence and severity of dental fluorosis in the United States, 1999-2004. NCHS data brief, no 53. Hyattsville, MD: National Center for Health Statistics; 2010.  Available at: http://www.cdc.gov/nchs/data/databriefs/db53.pdf

Luke J. Fluoride deposition in the aged human pineal gland. Caries Res. 2001 Mar-Apr;35(2):125-8.

Whitford GM. The metabolism and toxicity of fluoride. Vol 13. Basel: S. Karger AG; 1996.