Tag Archives: Dental caries

It’s time we did something about sugar


I saw this image in the paper:

Sheiham, A., & James, W. P. T. (2014). A reappraisal of the quantitative relationship between sugar intake and dental caries: the need for new criteria for developing goals for sugar intake. BMC Public Health, 14(1), 863.

It’s a very graphic illustration of the central role played by dietary sugar in tooth decay. Certianly makes one think about how to drastically reduce our dietary sugar intake.

There are a couple of “take home messages” in the paper:

“Sugar is the primary cause of dental caries”

Ths seems to have been debated in the past but is now widely accepted. Because acid attack arising from sugar metabolism is the only mechanism for inducing caries:

“the only confounding factors i.e. tooth brushing and the use of fluoride in drinking water or toothpaste serve to reduce the magnitude of the simple relationship between sugar intake changes and caries incidence.”

However fluoride is not a “silver bullet:”

“although fluoride reduces caries, unacceptably high levels of caries in adults persist in all countries, even in those with widespread water fluoridation and the use of fluoridated toothpastes [21].”

We shouldn’t neglect adult tooth decay

Perhaps we have been underestimating the problem because the apparent improvement in oral health comes from considering data for children:

“The sugar-caries relationship in adults has been largely ignored: all the conclusions on safe levels of sugar and the relationship between sugar and caries are based on children’s data. With fluoride and greater dental care caries has declined in children so some dental authorities have concluded that sugars are not a major determinant of caries provided fluoride toothpaste is use diligently with or without water fluoridation. However, it is now evident that the majority of caries occurs in adults, not in children, because the disease is cumulative and the rates of caries in individuals tracks from early childhood to adolescence and then into adulthood [21,26]. So the conclusion that sugar is not the major determinant of caries, is simply wrong.”

The impact of fluoride

Anti-fluoride propagandists are already quoting this research – using the central role of sugar to imply this proves fluoride is ineffective. But the authors say:

“Fluoride is associated with about 25% lower caries experience when sugar intakes are constant between 10-15%E [10-15% of energy itnake from sugar]  in 12 year-old children [20]. The widescale use of fluoride toothpaste is a reasonable explanation for the decline in children’s caries in many countries since the 1970s, yet what then becomes relatively evident is that caries becomes more prominent in adolescents and adults [4,21].

Ireland has had a mandatory national water fluoridation policy since 1964 but some areas have not implemented the fluoridation policy thereby allowing a comparison within a country where fluoride toothpaste is in widespread use but drinking water fluoride varies. Additional benefits accrued from having fluoride in water as well as toothpastes but 7.3% of even the youngest adults aged 16-24 years with lifelong fluoride exposure still had dental caries experience in 4.6 teeth as did 53% of the 35-44-year-olds assessed 35 years after the beginning of water fluoridation: the mean DMFT was 13.3 and 16.0 in those living in non-fluoridated areas [15]. Australia has water fluoridation in a number of cities, but despite fluoride use from both toothpastes and drinking water the mean DMFT and DF Surfaces for all adults increased; adults aged 65 years and older had ten times higher levels of caries than 15–24-year-olds [16]. Thus although fluoride reduces caries, unacceptably high levels of caries in adults persist in all countries, even in those with widespread water fluoridation and the use of fluoridated toothpastes [21].”

So research is showing a strong need to cut dietary sugar intake by both children and adults.  The authors say “for multiple reasons, including obesity and diabetes prevention, we need to adopt a new and radical policy of progressive sugar reduction.” They conclude:

“that public health goals need to set sugar intakes ideally <3%E with <5%E as a pragmatic goal, even when fluoride is widely used. Adult as well as children’s caries burdens should define the new criteria for developing goals for sugar intake.”

Obviously community water fluoridation (CWF) remains an important issue in New Zealand because political activists still work hard to remove it, or prevent it when health authorities attempt its introduction. It seems to me, though, that CWF, once achieved, plays its important role without having to continually educate and encourage the population to change their dietary habits. The battle over sugar will be so much harder because it will involve social pressure to change personal habits, as well as countering all the anti-science and freedom of choice arguments.

At least local body councils, and immature local body politics, will not play a key role.

Similar articles




Cherry picking fluoridation data

Anti fluoridationists certianly go in  for picking cherries when the produce “evidence” to discredit fluoridation. Two anti-fluoridatioon actvists, Bruce Spittle and Russel McLean, did this in there opinion piece in the Otago Daily Times recently (see No consent given for fluoridation). In particular, they carefuly selected data from the Ministry of Health’s database on the oral health of children.

How to “prove” fluoridation ineffective

They claimed:

The efficacy of water fluoridation is modest.The Dental School staff referred to the 2009 New Zealand Oral Health Survey which noted that in 2008, for all of New Zealand, the 5-year-olds in fluoridated areas had a percentage caries-free rate of 58.7% compared to the rate of 55.0% for those in non-fluoridated areas. However, the 2011 figures show little difference, with the rate for fluoridated areas being 59.91% and that for non-fluoridated areas being 59.18%.

In this case, while they chose the total data set, they selected just 2 years (2008 and 2011), selected only one age group, considered just “percentage caries-free” and ignored the data for “decayed, missing and filled teeth,” and also ignored the data for Maori (important because these show the influence of social and economic deprivation).

I looked at the whole data set in my article Fluoridation – it does reduce tooth decay. So I will just repeat a few of my data plots from that article toi show the effect of cherry picking. The plots of the data below give an idea of variability and trends. They also show the influence of social and economic deprivation is long-term. (Click on the graphs to enlarge for details).





There could well be some story in the apparent reduction of the effect of fluoridation shown by the % caries free of 5 year olds but that has to be put into the context of the whole data set. It is dishonest to just select the small samples Spittle and McLean did – but of course you can see why they did select those years and restricted their comments to just 5 year olds and “% caries free.”.

How to prove fluoridation damages oral health

The Fluoride Free New Zealand Facebook page provides another example of cherry picking (see Waikato Dental Health Stats). In this case their “findings” were so ludicrous that you might have thought they would blush at presenting them. There are some mistakes in their data, but it tends to show that children had better teeth in the non-fluoridated areas than the fluoridated areas!

Well, they achieved this by cherry picking data for one year (2011) and one region (the Waikato). If we look at some of the data over the availabke time period (2002 – 2011) for Waikato, we can see why they cherry picked this region and year.


But, comparing the Waikato data with the total data in the previous figures we can see a greater variability from year to year. This variability makes any honest comparison very difficult – but it does give opportunities for creative cherry picking. (Yes, I have just “cherry-picked” the caries free data for 5 years old in this graph – but I am making a point).

Be careful of variation and cherry picking

The opportunities for cherry picking in a field like this are everywhere because of the variability. This is not like the data one gets in a carefully controlled laboratory experiment. We are dealing with a biological system – which introduces biological variability. But on top of that, it is also a social system which introduces an extra set of variability.

As an example, I was recently discussing with my granddaughter her new school in Hamilton. She told me that all her friends actually lived out-of-town. But the dental data will have recorded them as being from a fluoridated area because, at the time, Hamilton was fluoridated. Then there are problems of getting consistent evaluation from a large number of dental nurses. Differences in dietary intake, drinking of bottled water, etc., – the list goes on.

Some of this variation “evens out” when the data set is large (and of course has more influence when only part of the data set is chosen. Yes, it would be nice to control for all these social effects but in the real world one rarely gets the opportunity.

However, my point is that the variability introduced into this sort of data by biological and social effects provides ample opportunity for political activists to cherry pick data to support their own story – confirmation bias if innocent and dishonest misrepresentation if not.

So, it is easy to make claims one way or the other in the fluoridation controversy – and to find data to support these claims. But serious assessment of the claims requires critical evaluation of the data – something many people have no experience with.

This seems to have been the case with the Hamilton City Council who concluded from presentations heavily biased toward anti-fluoridationists that fluoridation of water supplies is not effective. But why should we expect city councillors to have the critical evaluation skills required to assess such data? They should never be put in the position of being asked to make scientific judgements in this way.

See also:

Similar articles on fluoridation
Making sense of fluoride Facebook page
New Zealanders for fluoridation Facebook page

Fluoridation – topical confusion

Please note the update below*

Some people claim both supporters and opponents of fluoridation agree on one thing. That the benfits of fluroide come from topical application  and not via systemic intake or ingestion of fluoridated water.

Well, that’s not quite correct. There is a semantic confusion. Researchers aret talking about mechanisms – that once teeth have erupted they are protected by the presence of fluoride in saliva and the biofilm on the teeth.  A topical mechanism of protection. This can come from procedures not involving ingestion – fuoridated toothpaste, fluoride varnishes and other dental applications, but also from fluoridated water passing the teeth during drinking. Some ingested fluoride can also contribute to salivary fluoride after metabolism.

Yet the anti-fluoridation activists commonly assert fluoridation of water does not work because, they claim, it doesn’t contribute to this topical mechanism. Effectively they  are choosing to interpret the topical mechanism as meaning a topical method of application or delievery is required.

The claim

Here’s the claim from the local Fluoride Action Network (FANNZ) (see 1. New science proves there is no benefit from swallowing fluoride):

The basic premise that swallowing fluoride prevents tooth decay has been disproved. When water fluoridation was first introduced en masse in the 1950s, dentists argued that fluoride needed to be ingested by children — while their teeth were developing — in order to be effective. The theory was that by swallowing fluoride it would accumulate in the teeth and make the enamel stronger and less susceptible to decay. However, since 1999 this theory has been rejected by all dental researchers (Featherstone 2000; Fejerskov 2004) and now the belief is that the primary benefit from fluoride is topical rather than systemic. That means it has to be applied to the teeth, not swallowed.

Well, we should all know that scientific knowledge is provisional and therefore changes as we accumulate more evidence. And we should be happy with that fact. But notice the word “applied. The awareness of a topical mechanism of action does not mean that fluoridated water is ineffective because it is drunk and ingested.

What researchers actually say

What did these researcher actually say? For example, FANNZ cite Featherston (2000). The paper is The science and practice of caries prevention, –  here is a quote from the abstract which I think is sufficient to make my point:

Fluoride, the key agent in battling caries, works primarily via topical mechanisms: inhibition of demineralization, enhancement of remineralization and inhibition of bacterial enzymes. . . . . . Fluoride in drinking water and in fluoride-containing products reduces caries via these topical mechanisms. “

Far from a topical mechanism excluding a protective effect from fluoride in drinking water it actually provides a mechanism for fluoridated water to be effective becdause it is incorporated into the saliva and biofilms during drinking..

The  review article Mechanisms of Action of Fluoride for Caries Control by Buzalaf, Pessan, Honório, and ten Cate JM (2011) shows the context for the topical mechanism in the diagram below.


Dynamics of minerals in saliva and enamel under neutral (a, b) and acidic conditions (c, d). (Buzalaf et al. 2011).

Read the review for the details, but basically it involves fluoride present in saliva and the biofilm on the tooth surface reacting with calcium and phosphate dissolved during acid attack and producing an insoluble F containing bioapitate which is incorporated into the tooth structure because it has a lower solublilty than the bioapate which doesn’t contain substituted F.

The frequent drinking of the fluoridated water supplies F at an appropriate concentration to the tooth suraces, biofilms and saliva. So the review concludes

“More than 60 years of intensive research attest to the safety and effectiveness of this measure to control caries. In this case, however, it should be emphasized that despite being classified as a ‘systemic’ method of fluoride delivery (as it involves ingestion of fluoride), the mechanism of action of fluoridated water to control caries is mainly through its topical contact with the teeth while in the oral cavity or when redistributed to the oral environment by means of saliva. Since fluoridated water is consumed many times a day, the high frequency of contact of fluoride present in the water with the tooth structure or intraoral fluoride reservoirs helps to explain why water fluoridation is so effective in controlling caries, despite having fluoride concentrations much lower than fluoride toothpastes, for example. This general concept can be applied to all methods of fluoride use traditionally classified as ‘systemic’. In the light of the current knowledge regarding the mechanisms by which fluoride control caries, this system of classification is in fact misleading.”

As well as this topical mechanism for protecting exisiting teeth the current research still indicates some health benefits from ingestion:

“Evidence also supports fluoride’s systemic mechanism of caries inhibition in pit and fissure surfaces of permanent first molars when it is incorporated into these teeth pre- eruptively.”

Ingested fluoride can also benefits bones – see my article Is fluoride an essential dietary mineral? for more on this.

Contribution from topical methods of delivery

The review I quote above also discusses these other methods of fluoride delivery like fluoridated toothpaste and dental treatments like varnish and fluoride gel applications. In these cases the fluoride is delivered at a much higher concentration and reacts with calcium to form calcium fluoride crystals. These have a low solubility but can release fluoride at the low concentrations suitable for providing protection to teeth by the topical mechanisms discussed above. They effectively act as fluoride reserviors near the teeth.

Despite the effectiveness of these methods of delivery they usually have disadvantages because of the high concentrations of fluoride involved. Problems can arise if they are accidentally or intentionally ingested. Young children are also prone to poison themeselves if such materials are left in unsecure places.

Saliva fluoride from ingested water

FANNZ has also tried to make an issue of the low concentratio of saliva F derived through metabolism of ingested fluoride. In fact, they sometimes claim that advocates of fluoridation still present that as the main method of delivery. The quote from their website above goes on:

“Dentists continue to promote fluoridation as they say there is also a smaller benefit from swallowing fluoride because it gets into peoples saliva and helps to remineralise the teeth.”

FANNZ continues that claim in their criticism of expert evidence presented to the Hamilton City Council hearings on fluoirdation. This then enables them to divert attention away from the delivery of F to tooth surfaces during drinking of fluoridated water. This is what they say about saliva F derived from ingested water. After claiming that saliva F derived from metabolised forms is insufficient to confer a topical benefit they quote from the CDC report Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States:

“The concentration of fluoride in ductal saliva, as it is secreted from salivary glands, is low — approximately 0.016 parts per million (ppm) in areas where drinking water is fluoridated and 0.006 ppm in nonfluoridated areas. This concentration of fluoride is not likely to affect cariogenic activity.

Looks convincing, eh? But, and this is important, they stop their quote there, omitting the important following sentences:

“However, drinking fluoridated water, brushing with fluoride toothpaste, or using other fluoride  dental products can raise the concentration of fluoride in saliva present in the mouth 100-to 1,000-fold. The concentration returns to previous levels within 1–2 hours but, during this time, saliva serves as an important source of fluoride for concentration in plaque and for tooth remineralization.”

So, in reality, the report they quote, and especially the part they intentionally omit says the complete opposite of what they claim about that report:

“The CDC acknowledges that fluoridated water has no cariostatic effect.”

The complete opposite. The CDC acknowledges nothing of the sort.

Unfortunately I am finding this sort of blatant misrepresentation and distorting is very common in the FANNZ propaganda. I urge readers to approach their literature with caution. To think critically (as one always should) and to actually check their citations by reading the originals.


FANNZ has sort of responded to this article at Misleading claim against FANNZ of misrepresentation.

It’s a confused response relying on a bit of strawmannery, irrelevant chemical assertions and an unjustified assumption that F in fluoridated water can not possible have a topical effect. So I will just make a few points:

1: It is normal to reference and link to an article being criticised. FANNZ didn’t do so – perhaps they want to avoid readers checking out my article?

2: Nowhere did I claim that drinking fluoridated water caused F concentrations in the mouth to magically increase to 16 ppm by a “chemical mechanism by which the saliva “sucked” the Fluoride out of the water in the fraction of a second it passes over the teeth.” Strawmannery.

3: FANNZ assumes that F has no topical effect at concentrations in fluoridated water (0.7 – 1.0 ppm). They justify this by citing 5 cherry-picked papers and ignoring papers which don’t support their assumption. The sources they use refer to studies made at high concentrations (considering topical application methods) or with sugar solutions.

The chemistry of F in saliva and at the tooth surface and subsurfaces is complicated – influenced by both thermodynamic equilibria and kinetic factors. Then influence of F depends on concentrations of Ca and phosphate, pH and organic material present. One should be very careful about extending findings from one situation to other situation.

As well as completely ignoring the conclusions in the CDC report they reference, FANNZ choose to ignore, for example, Featherston (2000)** who says:

“The cariostatic effects of fluoride are, in part, related to the sustained presence of low concentrations of ionic fluoride in the oral environment,derived from foods and beverages, drinking water and fluoride-containing dental products such as toothpaste. Prolonged and slightly elevated low concentrations of fluoride in the saliva and plaque fluid decrease the rate of enamel demineralization and enhance the rate of remineralization. For example, fluoride at 0,04 ppm in saliva can enhance remineralization.” [my emphasis]

**Featherston, JDB (2000). JADA, 131 887-899. “The sciuence and practice of caries prevention.”

See also:

debunking anti-fluoridation arguments
Fluoridation and conspiracy theories
Fluoridation – the violation of rights argument.
Poisoning the well with a caricature of science

Getting a grip on the science behind claims about fluoridation
Is fluoride an essential dietary mineral?
Fluoridation – are we dumping toxic metals into our water supplies?
Tactics and common arguments of the anti-fluoridationists

Fluoridation – it does reduce tooth decay

In the current fluoridation debate anti-fluoridation activists will often claim fluoridation of public water supplies actually doesn’t reduce tooth decay. This conflicts directly with the advice of our health authorities – so what is the truth?

The claim

Again I will directly consider the claim of the Fluoridation Action Network of NZ (FAANZ). It’s summarised in the first objection to fluoridation (1. New science proves there is no benefit from swallowing fluoride ):

There are numerous modern studies to show that there is no difference in dental decay rates between fluoridated and non-fluoridated areas. The most recent, large-scale one was conducted in Australia (Armfield & Spencer, 2004 Community Dental Oral Epidemiology. 32:283-96).

When you observe the statistics of the world they clearly show tooth decay has declined in both fluoridated and non-fluoridated areas alike. This is a trend that is demonstrated when viewing the statistics across the States in America and in the smaller counties. See the charts and findings by Dr. Bill Osmunson in the above video by Professional Perspectives.

In New Zealand there have been two recent studies that showed there was no difference in dental decay for permanent teeth. One was the Southland Study in 2005 and the other was the Auckland study in 2008. These, among many other studies, have proven water fluoridation to be ineffective.

(This objection goes on to discuss topical vs systemic intake of F which I won’t discuss here)

But, health authorities in New Zealand disagree – and they have the data to support their case. So how credible is the FANNZ claim?

The citation.

Again, another citation, unlinked, so I had to go to the trouble of hunting it down to read what it actually does say – which turns out to be the exact opposite of FANNZ claim! Same problems I met when I looked at their claim about toxic elements in fluoridating agents (see ).

The Australian study (Armfield& Spencer, 2004 Community Dental Oral Epidemiology. 32:283-96) investigated concerns about the high use of bottled and rainwater. Several social, economic and dietary factors were considered but the major significant effect was that of fluoride. Children consuming tank and bottled water had much higher carries than those consuming water from fluoridated public water supplies. This was found for deciduous teeth, but not for permanent teeth and the authors speculated on the dietary and other reasons for this. They concluded:

“This study demonstrates the continued community effectiveness of water fluoridation and provides support for the extension of this important oral health intervention to populations currently without access to fluoridated water.”

The authors considered lack of fluoride is an important problem for tank water use saying:

“Efforts could be directed at either reducing the use of tank water for domestic drinking water consumption or further encouraging the appropriate use of fluoride to compensate for the lack of fluoride in the drinking water.”

About bottled water they say:

“consumers currently have little choice in Australia and the imminent introduction of fluoride-containing bottled water does not look likely.”


“It is also time that bottled water manufacturers in Australia began marketing fluoridated water. In the US more than 20 companies produce water with optimum fluoride concentrations.”

They finish their paper with this:

“Bottled water is promoted as a healthy, chemical-free alternative. There is a need for bottled water manufacturers to take a stand on the issue of the benefits of appropriately fluoridated water and provide consumers with choice.”

So another example of FANNZ using a citation inappropriately – to support a claim the exact opposite to the study’s results.

The New Zealand data.

The Ministry of Health (MOH) keeps records on the oral health of New Zealand children – and anyone can download that data from their website. There is data for age 5 and year 8 children over the time period 1990 to 2011. I’ll have a detailed look at the data for 2002 – 2011 (earlier data doesn’t include the ethnic breakdown which is very relevant). But first a few comments about the way many of the anti-fluoridation activists are cherry picking this and similar data to support their arguments.

Recently I received two specific claims made about this data:

  1. The oral health of Christchurch people is better than for New Zeland as a whole. The don’t have access to fluoridated water therefore this proves fluoridation doesn’t work.
  2. In 2011 the mean number of decayed, missing and filled teeth in 5 year old Waikato children was greater for children drinking fluoridated water than for those drinking unfluoridated water. This proves fluoridation doesn’t work.

In both claims data was carefully selected to “prove” fluoridation doesn’t work. One can’t directly compare Christchurch data with that for the whole of New Zealand as that ignores the influence of ethnic, social and other factors. And selection of one small piece (Waikato in 2011) of the total picture cannot give you any idea of that total picture. The data includes all sorts of variation over time and region and these cherry-pickers are make cynical use of this.

I have summarised the MOH data in this table as the changes for the percentage of carries free teeth, and mdmf – the mean number decayed, missing and filled teeth per child per year. The data are for 2 age groups and are averages, over the period 2002 to 2011, of annual data . The totals and the separate data for Maori give some idea of differences which are probably largely a result of the well established social and economic disadvantage of Maori.

Effect of fluoridation of % carries free and mdmf

Year 8

Total Maori
Carries free (%) 8.86 10.42
MDMF* -0.48 -0.81

5 years

Total Maori
Carries free (%) 8.05 12.46
MDMF* -0.63 -1.38

*MDMF = Mean decayed, missing and filled teeth

I think that shows fluoridation is associated with a clear increase in numbers of carries free teeth, and a clear decrease in the mean decayed, missing and filled teeth.

So much for FANN’s claim “that there is no difference in dental decay rates between fluoridated and non-fluoridated areas.”

The figures below show the data graphically to enable readers to get a better understanding.

First a comparison of average annual % carries free teeth and mdmf in the period 2002 -2011 for the two age groups.

% carries free


Mean decayed, missing and filled teeth


Plots of the data below give and idea of variability and trends. They also show the influence of social and economic deprivation is long-term.

% carries free




A comment in trends

Some anti-fluoridationists are making an issue of the apparent improvement in oral health for people consuming unfluoridated as well as fluoridated water. For example, the claim above asserts:

“When you observe the statistics of the world they clearly show tooth decay has declined in both fluoridated and non-fluoridated areas alike.”

Perhaps they think that this somehow covers up the fact that despite the trends oral health it is still better for the fluoridated groups.

Mind you, another reason is that many of the statistics they refer to are presented only graphically. For example this figure from Fluoride Alert (an anti-fluoridation group) actually does not correspond to the data it refers to.


It seems the figure was constructed using only 2 data points of each line – 1 very old and 1 recent. This means that all sorts of factors, (such as changes in criteria and attitude of dentists towards saving teeth) could be involved – quite apart from fluoridation.

The data I have plotted above the New Zealand in the period 2002 – 2011 does not show the declines that the anti-fluoridationists claim.

Another example of cherry-picking to mislead.

See also:

Getting a grip on the science behind claims about fluoridation
Is fluoride an essential dietary mineral?
Fluoridation – are we dumping toxic metals into our water supplies?
Tactics and common arguments of the anti-fluoridationists
Hamilton City Council reverses referendum fluoridation decision
Scientists, political activism and the scientific ethos

Similar articles

Is fluoride an essential dietary mineral?


Source: Dietary Minerals, Wikipedia

Anti-fluoridation activists often assure us that fluorine (F) is not an essential element. But what does that mean? Literally I guess it means that there are no identified biological pathways essential to human life involving F. So anti-fluoridation activists often claim the only safe level of flourine in the human diet is zero!

But whether an element is essential or not is often unclear or undecided. Some sources claim about 16 elements seem to be essential to maintain life. Others claim over 20 elements are essential.

Fluorine is rather debatable, as the above Periodic Table of the elements suggests. The Wikipedia entry on Dietary Minerals does say, however:

“Fluorine (as Fluoride) is not generally considered an essential mineral element because humans do not require it for growth or to sustain life. However, if one considers the prevention of dental cavities an important criterion in determining essentiality, then fluoride might well be considered an essential trace element.”

So F may well be considered an essential trace element, or a beneficial element. By the way, we should not let the fact that F is known to have harmful effects when in excess lead us to deny its beneficial effects. Probably all essential or beneficial elements and trace elements do.

Essential and beneficial elements usually display a “beneficial window” of  intake. This can be shown by a U shaped  graph when we plot the incidence of negative effects against intake (see figure below).


Source:  Howd & Fan, 2007 –  Risk Assessment for Chemicals in Drinking Water page 202.

So we expect to see that sort of relationship with F intake if the element is essential, or even just beneficial. If there are no benefits from F we would expect only an increasing incidence of negative effects when the intake increases from zero. Of course we also see that for essential or beneficial elements if we restrict our data to only high levels of intake.

Does F have benefits besides dental ones?

Do the benefits of F extend more widely than the prevention of dental cavities? I have often thought they do because F has a clear effect on the structure and solubility of hydroxyapatites – an important and major componet of bones. A small amount  of substitution of F for OH in the hydroxyapatite structure can strengthen such minerals and lower their solubility. Bioapatites are a major component of our skeletons, and play a role in many of our organs. This chemical substitution may actually have positive effects on bone health, and the properties of other bioapatites. Of course excessive substitution, or differentiation into different chemical crystalline phases, may also have negative effects when there is excessive intake.

By the way, F is not the only elements that substitutes at trace levels in bioapatites. There are many more and they can each influence the properties of the bioapatite.

Another way of looking at this is that pure chemically defined compounds rarely exist in the real world. Other minor elements are often incorporated into the crystal structure, or be present in a closely associated crystal phase.  These “impurities” or substituted elements usually impart features to the natural material which are greater or lesser than, or perhaps not even seen, in the pure compound. These features can be important to the biological role of crystals in nature and life.

Because biological systems are always exposed to a whole range of chemical elements at varying concentrations there will be no such thing as zero F intake. Nobody’s body is “fluoride free.”

Beneficial effects of F on human bones?

I recently checked out a paper which shows beneficial effects  of F on human bones along the lines I have suggested.  The paper is Yiming Li et al., (2001): Effect of Long-Term Exposure to Fluoride in Drinking Water on Risks of Bone Fractures. The authors are a group of researchers from the US and China. You can download the PDF here and check out methodology and other details.

Here’s one of the figures from their paper summarising the relationship of overall bone fractures to F content of the water supply used.


Effectively, this displays the U-shaped curve mentioned for essential elements in Risk Assessment for Chemicals in Drinking Water.

Or, perhaps more importantly – statistically significant increases in numbers of bone fractures occur at both low levels of fluoride in drinking water (<0.3 ppm) and at high levels (>4 ppm).

The authors express it this way:

“The data appear to suggest that there may be a “beneficial window” of fluoride intake for bone health, because an increased risk of overall bone fractures was detected in both the populations with deficient and excessive fluoride in drinking water.”

Not surprisingly this window corresponds approximately to current New Zealand advice for oral health  – concentrations of fluoride in the water supply in the range 0.7 to 1.0 ppm are beneficial.

So perhaps we should consider F as an essential, or at least, beneficial trace element as Wikipedia suggests. And perhaps health authorities in New Zealand should include bone health, together with oral health, in their advice on fluoridation.

The quality of research studies is critical

Other groups have produced similar conclusions to that of Yiming Li et al. – particularly that the incidence of bone fractures are reduced by fluoride doses in the beneficial range of F intake. But, these sort of investigations are very complex so it’s possible to find other studies which don’t show this result, or show only the effects of high fluoride intake. This raises the question of the quality of such investigations and the need for readers and reviewers to be particularly informed about such issues.

Many of these sorts of studies produce results of questionable quality because they ignore the role of other factors besides F in the water supply. For example, in many developed countries, and many developing ones, dietary intake of fluoride also comes from toothpaste, mouthrinses and dietary supplements. The high mobility of modern populations also makes it difficult to relate clinical effects to simple factors in the current environment of the individuals. It’s no wonder that attempts to relate health effects to fluoride concentrations in the public water supply produces controversial findings.

Mind you, that’s a great gift to the unscrupulous cherry-picking, uncritical reviewer with an ideological or activist axe to grind. If you are selecting studies to support a preconceived viewpoint the influence of other factors is not important – you just choose what suits your argument and ignore the quality. But if you are trying to establish a reliable picture of what is actually happening, as we hope our health professionals and scientists are, it’s important to consider the quality, and reliability, of each study.

My impression is that this particular study is considered of high quality because it used populations with a defined history of fluoride exposure. The authors say:

“In contrast to the U.S. population, residents of rural China rarely change residences, and most have been using the same water supply throughout their life. Because of its unique environmental and cultural conditions, such as virtually no residential mobility and a relatively consistent lifestyle, rural China has been considered a perfect “living laboratory” for studying the relationship between various factors and diseases. The survey results of our study sites and data from individual subjects show that fluoride exposure in rural Chinese communities is still limited to water and diet.”

And in their methodology:

“The residency of each subject was determined by the following three measures: (1) objective assessment by checking the Family Registry Book, an official document issued by the government; (2) a subject survey questionnaire; and (3) confirmation by village officials who were familiar with the subject.”

This sort of reliability of information is just not available for modern populations in most countries, making these sort of studies unreliable.

The lesson here is that there must employ intelligent and expert consideration when reading or reviewing research in this sort of area. People consulting such studies and reviews should also be aware of the dangers. When public debates, like that over fluoridation, occur we need to be aware of the way activists may draw unreliable conclusions from the literature and promote those unreliable conclusions to the public.

As an aside – this study also considered possible effects of factors like gender, smoking and alcohol – not surprisingly bone fracture were higher for men, and for those consuming alcohol!


So, is fluoride an essential element? I don’t know and I am hardly the person to decide. But clearly it is possible to argue the case that it may be, or that it is at least a beneficial element, provided dietary intake is neither too low or too high. It’s a complex area – just beware of activists with an axe to grind and a simple picture to support their claims.

See also:
Fluoridation – are we dumping toxic metals into our water supplies?
Tactics and common arguments of the anti-fluoridationists
Hamilton City Council reverses referendum fluoridation decision
Scientists, political activism and the scientific ethos

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