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Fluoride in UK Tap Water: Arguments For/Against Fluoridation and Missing Data on Dental Decay

What is fluoride? 

Fluoride is a mineral complex, whereby the mineral is combined with fluorine. Fluorine is a halogen, belonging to the same family as bromine, chlorine and iodine. Its simultaneous listing as an industrial pollutant and an additive to municipal water supplies has fuelled dispute over its role in human health. Such controversy has been elevated with the recent announcement by the UK Government that they are to expand the fluoridation policies from a small number of areas to the entire country.

So what are the arguments?


Justification from those who support fluoridation

  1. Fluoride reduces caries

21 years ago, a meta-study of 214 previous papers determined that fluoridating water reduced number of dental caries by 2.25 teeth, or reduced the number of children with caries by 14.6%. The same study showed that 12.5% of children receiving fluoridated water developed fluorosis, although supporters of fluoridation believe that this is a trade-off worth making.

A 2014 study compared West Midlands, an area with extensive water fluoridation, to the North West, an area with untreated water. The latter was shown to have 5.7x more hospital admissions for dental caries (which, when the assessment was made only for the Primary Care Trusts in most deprived areas, the difference became 12-fold). Of course, this data is not measuring the absolute rate of dental caries, but has been accepted as a suitable proxy by supporters of fluoridation.


  1. Fluoridation creates ‘dental equality’

It is clear that caries is a health concern that disproportionately affects deprived communities. The 2014 NHS England report on dental health shows that those in the most-deprived communities are over 4x more likely to get tooth decay than those in the most prosperous. It is therefore a logical deduction that those in the poorest areas can be expected to receive the most reduction in dental caries from fluoridating municipal water.


Concerns from those who oppose fluoridation


  1. Fluoride does not / cannot provide the claimed benefits

The meta-study mentioned above (from 2000, 214 papers included) is mainly made up of studies conducted 40-60 years ago (when dental health was substantially worse than today); 80% of these included studies were conducted in before 1985. This is particularly relevant because, in the UK, the number of decayed/missing/filled teeth in children dropped by 77.4% between 1980 and 2006. The same report determined that the average number of decayed/missing/filled teeth in British 12-year-olds is now just 0.7. Accordingly, less baseline decay means less benefit in fluoridating the water (but the same systemic side-effects). The data from previous decades is sketchy but the best indications we have here decades comes from the Country/Area Profile Project, which indicates that in, between 1960 and 1985, the average number of Decayed, Missing or Filled Teeth came in at between 3 and 4 per child (in other words, we can expect number of children vulnerable to caries has dropped by over 70% since the majority of these studies was completed, and therefore the amount of teeth ‘saved’ by fluoridation will drop accordingly).

This is an important point. The original assessment determined that the NNT (Number Needed to Treat) in order to avoid one child developing dental caries was six. In other words, for every six children that were fluoridated, one child avoided tooth decay (when they were otherwise destined to do so). The problem is twofold: one in eight developed fluorosis. In other words, the NNH (Number Needed to Harm) is eight.

In the modern era, where there is less than a quarter of the dental caries, there is less than a quarter of the benefit. The adjusted NNT becomes 26.5 children. That’s more than 3 incidences of fluorosis for every one incidence of dental caries saved.

The WHO data collected by SAPP also provides useful information the need for fluoridation. As seen in the graph below, the rates of dental decay have dropped heavily in all countries studied, with non-fluoridated nations recording more substantial improvements than those added fluoride into the water. The takeaway here is that fluoridation is just one strategy to improve dental health and that good dental hygiene may render this unnecessary (especially given the rates of fluorosis it induces).

This data makes a strong case to re-evaluate the relevance of the old data. After all, it is mathematically impossible for fluoridation to reduce the development by an average of 2.25 cavities per child when the average child only experiences 0.7 cavities, yet that is the current evidence being used to justify fluoridation.

So what can we make of the 2014 study that showed such an impressive effect on dental health? As always, the devil is in the details, specifically the fact that this study did not measure the reductions in dental decay. It measured the number of dental procedures performed in hospital (rather than at a dentists’ office) in West Midlands SHA versus that in the North West SHA, an area that is largely unfluoridated. It is always a concern when researchers use such indirect metric to estimate the relate of dental decay, and especially so when estimates are used for an outcome that government researchers already have access to (dental procedures are recorded by NHS, who perform the majority of dental work in the UK). The extrapolation becomes bizarre if we consider that West Midlands SHA, the area under focus in this study, was specifically targeted by the Government in the years prior, with dentists spending 2.2x more per child than previously and performing 55% more preventative work in their offices. It figures that, if more is being done to prevent tooth decay and more work is being conducted at dentist’s offices, then they may be both more decay and a higher proportion of this being handled in hospitals. In other words, this metric is no longer flawed. It is rotten. It appears implausible that the public health authorities simply made a massive mistake in using it.

Several researchers commented on this; while stopping short of outright calling the study corrupt, they sensitively noted that the two regions were missing 80% of the relevant data (an issue that would make both highly questionable choices for comparison). They also pointed to the huge dental spending gap and highlighted the likelihood of cherry picking; these two areas just so happen to have the largest contrast in outcomes (West Midlands has unusually good figures for a fluoridated area, while North West has unusually bad outcomes for an unfluoridated area).

Perhaps the last word should go to the authors of this study. They provided no explanation of why they chose not to measure rates of tooth decay but acknowledged “contemporary UK specific reports of clinical trials on the efficacy of water fluoridation remain understandably absent”. If this is about health benefits, why do those promoting fluoridation seem so keen to not study its health effects?


  1. Fluoridation is harmful for teeth

Fluorosis is the term used describe the hypomineralization of teeth caused through excess fluoride ingestion. This sees visual changes in the colour and lustre of teeth (with opaque white patches occurring in the most mild cases, and dark pitted teeth being found in more serious cases).  While proponents of fluoridation dismiss this as ‘only’ cosmetic harm, critics plead that the mental health of children be considered. I suspect that very few children who have been ribbed by his or her classmates for having ‘tippex teeth’ would argue with this.

The 2000 meta-study found that fluoridation induces fluorosis in 12.5% of children.


  1. Flouride is neurotoxic

A meta-study by the Harvard School of Public Health pooled the results of 27 prior investigations into the effect of fluoride exposure on neurological development. They found that the average IQ drop was 7 points (on the standard scales). This is frightening, especially because this relates only to the average drop; the mechanics of how fluoride disrupts brain development are not yet confirmed but, if we consider the basic principles of toxicology and standard pathophysiological reasoning, it seems inevitable that those with poor physical health will be most affected. That is to say, those in good health may not suffer as much while those without good nutritional status will be hit hardest. The undisputed link between socioeconomic status and physical health (and the obvious conclusion that deprived children will be hit hardest) makes a mockery of the idea that fluoridation is important for health equality.

There are further concerns beyond simply what will happen when children consume more fluoride; fluoride crosses the placental barrier. Increasing exposure of a known neurotoxin to a developing foetus opens up our society to an irreversible damage of vulnerable neurons and a further increase in developmental disorders (already at an unprecedented level). No research has been commissioned to look into this.


  1. Other health effects

It makes sense that, given their extreme similarities, that an item known to impact on dental health may also impact on bone health. And indeed it does. At sufficient doses, fluoride can accumulate in bones and cause a condition called Crippling Skeletal Fluorosis (CSF). How much of a dose is sufficient? A 1993 investigation found that 2mg per day was enough to induce the most serious stage of this condition. Fluoridation of the water will make this level achievable from just two litres of tap water per day (the amount we are recommended to drink).

It is important to point out that many people do not experience fluoridation of bones at this level. What makes some more vulnerable than others has not yet been explored (although iodine status is likely to play a role, given the competition between iodine and fluorine for cellular update). What is clear though is the impact of fluoride on bone health, with studies showing increased hip fractures (27% increase in women, 41% in men) elderly communities with fluoridation at 1ppm, compared to controls.

It is naturally a concern that, given the needs of the thyroid gland for iodine and the structural similarities between this element and iodine, that fluoridation may have implications for thyroid health. Such concerns were supported by research in Iran that found that fluoride could impact on thyroid health even at just 0.5mg/L (half that proposed by the UK government), with distortions in both TSH and T3 recorded. Further papers (here and here) have demonstrated the mechanism is indeed an inhibition of iodine update.

The direct impacts of fluoride have also shown to be worthy of concern, with fluoride’s effects on disrupting the gastric barrier highlighted in tests, which show how fluoride degrades mucus and reduces function of acid-secreting cells, and fluoride levels have been well correlated to higher rates of gastritis and ulcers.


  1. Fluoridation is a political policy, not medical

The argument extends outside of the number-crunching. Alongside the release of a 2015 paper by  Public Health England, Dr Sandra White (the director of dental public health) stated that fluoridation provided undisputable benefits but provided no data to support the claim. Skeptics pointed out that, after decades of fluoridation in the West Midlands, Tyneside and Warwickshire, there should be ample studies to quantify the effectiveness of the policy. Indeed, the only available paper that has provided support for the policy was the 2014 mentioned above (which was subject to bizarre indirect metrics, extreme cherry-picking and important funding gaps in dental care in the two areas). Indeed, the authors of this much-quoted study point out that there is no actual data to support fluoridation in the UK (something Dr White, perhaps predictably, repeatedly fails to acknowledge).

So, as has become de rigueur in recent years, we have a public health policy for which there is ample reasons for concerns but no relevant evidence to support its use and an ongoing refusal to undertake the usual safety checks. Equally, such a controversial policy just so happens to benefit multinational companies (in this case the aluminium and phosphate fertilizer industries, who no longer need to pay for removal of their fluoride waste and can now sell it to the government). So we have tens of millions of pounds of taxpayer money being spent on buying up this waste, but not a single study undertaken to track the effect of doing so.


  1. The fluoride compounds added to our water are industrial waste


One continual point of contention is the use of industrial waste products to fluoridate the water supply, with fluorosilicic acid the predominant form used for the treatments. This has been billed as a ‘win-win’ by authorities like the EPA, for whom administrator Rebecca Hanmer is quoted as far back as 1983 in describing the use of these waster products as “an ideal environmental solution to a long-standing problem” and one that provided water companies with “a low-cost source of fluoride available”.

Much criticism has naturally followed, with spectators focusing on two main issues: If the waste was previously causing such environmental pollution issues, should we be adding it into our water? And how can we know the impact of this chemical form that has never been studied?

Proponents have correctly pointed out that, as much as humans are predisposed to worry about drinking compounds that were previously considered environmental pollutants until added to their water supply, fluorisilicic acid quickly breaks down into sodium fluoride when exposed to a base salt (like sodium hydroxide). And indeed the chemistry is correct. But there is one issue, in that most naturally occurring fluoride is in calcium fluoride form.

Is there any functional difference between calcium and sodium forms? Yes. There is substantially less absorption of fluorine when bound to calcium. An important detail that has received scant attention.


  1. We don’t have to decide

One thing that both sides of the debate agree on is that there are positives and negatives to water fluoridation. The disagreement comes from the weighting given to each, ie. the age-old dilemma of what is in the ‘greater good’ and that the cost of increased fluorosis and neurodevelopmental problems is worth paying to reduce rates of decay. Beyond the points made above (which show that there is no possibility that fluoride could provide the level of claimed benefits), other critics of fluoridation make the case that there is not even a need to do this hedonic calculus, because the available data tells us that the desired dental outcomes can be achieved without fluoride.

Indeed, the NHS England report mentioned above lays bare the disparity in dental health between rich and poor (who have more than 4x more tooth decay). Indeed, a recent paper tracked 1035 mother-infant dyads and showed very strong correlations between socioeconomic status, quality of diet, dental health and obesity. Studies have found entirely expected mechanisms that link poverty to dental health; socioeconomic status was again found to be a big deal when it came to both tooth brushing and dental outcomes in an Egyptian study. There were no surprises in a 2018 French study  which found that those maintaining healthy eating habits were 60% more likely to brush their teeth twice per day, while those with higher socio-economic status were 25% more likely.

Such studies speak to both the role of tooth brushing but also that of other factors Perhaps unsurprisingly, an array of studies have found sugar intake to be the biggest determinant of tooth decay. A Finnish study tracked the dental health of 33 children over their first 10 years, and found that those with high sugar consumption averaged 1.4 dental caries, while those with low consumption only averaged 0.5 (a 64% reduction). A larger study (on 510 three-year-olds) in Brazil reported similar findings; this study only tracked the children for a year, but found that those consuming more than 32.6g of sugar per day had 3x the dental caries of those consuming less than 32.6g (low-sugar = 66% reduction).

The conclusions provided in the literature are re-enforced by unintended real-life experiments, with a 2014 paper pointing to when Nigeria was unable to import sugar and tooth decay fell to just 2%. The pattern was the same in Japan, during and following WWII. For reference, dental charities estimate the rate of tooth decay in the UK to be 36%.


In short, the argument can be summarized as this: better outcomes can be achieved by addressing the root causes (inequality and sugar intake) and doing so would achieve benefits far beyond simply dental health. The only parties that would lose out is aluminium/fertilizer manufacturers who would no longer have their waste products (fluorosilicic acid) to sell, the food companies who profit from selling sugar-laden cereals (and more) to children and corporations that benefit from the current financial system that redistributes wealth from the poor to the rich.




It is clear that, when it comes to dental caries, there is good support for the concept. The mechanism is feasible and supported by real-life data. However, the arguments depend on the rates of tooth decay being sufficiently high to warrant an intervention; evidence supporting its effect in modern populations is conspicuous by its absence. In other words, even if we are to hypothesize a ‘best-case scenario’ for fluoridation using the friendliest figures that have been produced in the last century, the case falls well short.

Such problems leave the case for fluoridation in tatters before we even consider the side-effects. To this end, the available literature makes it clear how easily fluoridation could damage our health but, once again, high-quality data to quantify these risks is still missing.


Where we’re at

The playbook appears to be less original with every round of corporate capture that occurs; in their predictably breathless attempt to support corporate policy, the fact-checkers argue that there is no need to worry about water fluoridation. What is the basis of their argument? Do they provide links to obscure studies that demonstrate that 2mg per day of fluoride is free of health effects, after all? Nope. They argue that fluoridation is safe because you can swallow 10g of toothpaste per day without breaching the toxicity limit set by the US Government (which has the highest recommendations of fluoride concentrations on fluoride in the water and sets upper limits at 10mg per day).

They don’t stick with the point long enough to consider the flaws in such a circular argument, with readers presumably left to conclude that ‘you can trust the government safety recommendations because they don’t flout the government safety recommendations’.


Action points

Aside from activism, several practical options stand out to counter unwanted fluoride exposure:

  • Using fluoride-free toothpaste. Such products are easy to find in any health store, but normally only recommended by holistic dentists.
  • Filtering your water. Options include countertop filters like the Big Berkey (with the additional fluoride filter* added) or reverse osmosis options, which undertake complete removal of contaminants in water and therefore need the beneficial salts to be added back in. Such approaches are normally hard-plumbed into your home but are available in countertop options like AquaTru (although this is not designed for use in hard-water areas).
  • Choosing low-fluoride dietary options. This centres on consumption of ‘regular’ and green tea, as the tea plant (camelia sinensis) is particularly capable of accumulating metals from its environment. As a consequence, there is widespread variability in the fluoride content that we can expect from a cup of tea, depending on its source (see resources below).


(NOTE: concerns have been raised about water samples showing raised levels of Aluminium after the use of these fluoride filters. This is due to the filters using aluminium oxide to bind up the fluoride; this is a chemically inert version of aluminium without the health concerns, but it is separated down into its ionic form when tests are performed. This process generates false positives for aluminium toxicity)



Resources – a lowdown of the fluoride content in a wide range of UK foods, as determined by researchers from Teesside University and Newcastle University in 2015 – test on 38 different tea brands available in the UK (TLDR: buy Japanese Sencha teas).



Any resources you think should be added above? Have your say in the comments…

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