Anti-fluoridationist’s flawed attacks on Calgary study


Image credit: Why I will no longer approve anti-fluoride dishonesty – New Anthropocene

The anti-fluoride propagandists are at it again – attacking a recently published scientific paper because the reported data does not fit with their own agenda.

The are attacking this paper:

McLaren L, Patterson S, Thawer S, Faris P, McNeil D, Potestio M, Shwart L. (2016) Measuring the short-term impact of fluoridation cessation on dental caries in Grade 2 children using tooth surface indices. Community Dent Oral Epidemiol 2016.

The Fluoride Action Network (FAN) claims the study is “fatally flawed” and that “key data [was] omitted.” The local FAN organisation – Fluoride Free New Zealand (FFNZ) has gone further claiming the study is “basically a fraud.”

Serious (even slanderous) accusations – let’s see if those charges hold up.

What did the study find?

The paper reports changes in dental caries levels of grade 2 children in Alberta, Canada between 2005/2005 and 2013/2014. Two cities were chosen – Calgary (which stopped fluoridation in May 2011 – after having been fluoridated since 1991) and Edmonton where fluoridation started in 1967 and is still in place. This enabled an assessment of the effect of fluoridation cessation on the dental health of children in Calgary.

Dental caries actually increased in both cities but the data shows a larger increase in dental caries where fluoridation had been stopped (Calgary) than where it continued (Edmonton).


defs = decayed, extracted (due to caries) filled primary tooth surfaces.

The change in Calgary (3.8) is greater than for Edmonton (2.1) and the difference is statistically significant.

The above graphic is for all tooth surfaces – similar results were obtained with smooth surfaces only – Calgary change = 2.9 and Edmonton change = 1.6.

Important features of study

There are several important features of the paper and the data reported:

1: Whereas previous cessation studies had used tooth-level data this study used tooth surface-level data. The authors had previously reported tooth level data which showed similar results.

The WHO prefers and recommends tooth surface-level data to evaluate an intervention such as starting or stopping fluoridation because of its greater sensitivity. The study authors used  tooth surface-level data and focused on smooth tooth surfaces which are most likely influenced by fluoride in this age group.

Most earlier fluoridation cessation studies had used less sensitive tooth-level data so this study was a definite improvement

2: A comparison (or “control”) city was used – Edmonton. Many previous cessation studies suffered from not using a comparison community. Interpretation is more difficult without some sort of “control” as changes due to other factors may be important. Factors like different assessment personnel, changes in diet (eg sugar consumption or bottled water), changes in dental health care, etc. It is difficult to take account of all factors but the inclusion of a similar comparison community helps reduce their effects on the results.

Again, this study was a definite improvement over previous cessation studies which had not used a comparison community.

3: Pre-cessation data were collected several years before cessation. The authors list this as a limitation, saying:

“it would have been preferable to have data collected closer to the year of cessation.”

However, this being the real world, the study used the only tooth surface-level data available for Calgary and Edmonton. There was absolutely no question of data being omitted (or “fraud”) that the anti-fluoride campaigners allege.

So how has FAN supported their charges?

Well, basically by retreating from (or ignoring) the advantages of this study – use of tooth surface-level data and use of a comparison community.

1: They use the limitation that the pre-cessation tooth surface-level data was collected several years before cessation to resort to more recent 2009/2010 data. But, importantly, that data is not tooth surface-level and it is for only one city – Calgary! 

So, they claim, the researchers “omitted key data” – the 2009/2010 data – pretending the researchers had  “hidden” it. But that data was not surface-level data. And, far from “hiding,” it the same research group specifically used this tooth-level data in an accompanying  paper:

McLaren L, McNeil D, Potestio M, Patterson S, Thawer S, Faris P, Congshi S,  Shwart L. (2016). Equity in children’ s dental caries before and after cessation of community water fluoridation: differential impact by dental insurance status and geographic material deprivation. International Journal for Equity in Health 15: 24

2: They ignore completely the importance of using a comparison community. Sure, they might claim that no survey was taken in Edmonton in 2009/2010. But they have thrown the baby out with the bath water in their attempt to discredit the research. They have fallen back on the limitation of so many fluoridation cessation studies which rely on cross-sectional measurements at different times without using a control. Worse still, they do this despite the tooth surface-level data for Edmonton showing an increase in dental caries even though there had been no cessation of fluoridation! They are willingly falling into the trap of ignoring all the other factors which could influence the results.

3: The FAN press release attempts to discredit the researchers saying:

“The lead author of the study, Lindsay McLaren, is not an independent scientist on the fluoridation controversy.”

This “damning by association” of researchers with their institutions, the fact that they receive a wage from their employers and that they write articles about their scientific results (which do not support the claims of the anti-fluoridation lobby) is really disingenuous. It’s a way of discrediting any scientist who produces results an anti-science group does not like. (Anti-science groups often use this argument – for example, anti-fluoride activists haver told me I am not “independent” because I once worked as a scientific researcher and,  therefore, cannot be trusted!).

Ironically, they are hanging themselves with their own rope on this one. Their press release makes mileage by quoting an assessment from an “independent” scientist Dr Trevor Sheldon. I checked with Sheldon and he confirmed that he:

“was invited to comment on this by Fluoride Action Network.  I did not have much time to do this but agreed to do so and received no incentive or reward.”

Now, doesn’t that admission  compromise Sheldon as an “independent” commentator? He immediately responds to a request from an activist political organisation, a group funded by the “natural”/alternative health industry – without any qualms! That confirms in my mind the links and political sympathies Sheldon has with FAN that I have long suspected.

It is perfectly normal (and healthy) for credible scientists to disagree with published papers and there are publication mechanisms to do this effectively. For example “letters to the editor” or comments in the specific journal – or even alternative journals. The fact Sheldon chose an almost immediate critique in the newsletter of a political activist group confirms to me that he is not “independent” on this subject and that he, in effect, belongs to the stable of “tame” anti-fluoride scientists FAN makes regular use of in their press releases. People like Bill Hirzy, Kathleen Theissen, Bill Osmunson, Hardy Limeback, etc.

Some other critical details

FAN relied on Sheldon’s evaluation for their main criticism but there are other details in that evaluation which I can comment on.

1: Sheldon would have preferred “a randomised controlled trial where areas are randomly allocated to start/cease water fluoridation.”

Yes, that would have been nice wouldn’t it.But the fact this has never been done – and Sheldon himself has never initiated such a trial – rather indicates how impossible such a trial is. The Cochrane review of community water fluoridation, which anti-fluoride campaigners love to misrepresent, commented on the silliness of such complaints:

But the fact this has never been done – and Sheldon himself (and similar anti-fluoride critics) has never initiated such a trial – rather indicates how impossible such a trial is. The Cochrane review of community water fluoridation, which anti-fluoride campaigners love to misrepresent, commented on the silliness of such complaints:

“particularly for research questions where evidence from randomised controlled trials is never going to be available due to the unfeasibility of conducting such trials. Community water fluoridation is one such area.”

2: He attempts to  extrapolate from tooth-level data to “fill in the gaps” in the tooth surface-level data. This highly speculative analysis allows him to conclude that most of the increase in dental caries shown by children in Calgary occurred before the cessation of fluoridation.

He accuses the researchers of making a “heroic assumption” but it seems to me the assumptions involved in his extrapolation are worse than “heroic.” Yet  the analysis enables him to make conclusions which seem to be derived more from confirmation bias than from intelligent analysis of the data. Especially as he ignored any data from Edmonton.

3:  He comments on problems resulting from population movements, confounding factors, assessment methods and staff differences, sample size differences, etc. But these are common problems when attempting to make sense of existing data. Importantly, these problems and worse, plague the cessation studies that anti-fluoride campaigners continually quote to support their claims that community water fluoridation is ineffective.


The Calgary/Edmonton study does not have the limitations of most fluoridation cessation studies – in particular, a comparison community was used and the more sensitive and appropriate tooth surface-level data was used rather than tooth-level data. The period between the first assessment and cessation is an admitted limitation but certainly does not indicate the omission of data or hiding data as anti-fluoridationists are claiming. There was just no intermediate data available.

The resort to speculative extrapolation of tooth-level data for only Calgary is disingenuous as it ignores the low sensitivity of that data and the influence of other factors compensated for by the use of Edmonton as a comparison community.

Anti-fluoridation campaigners often make ready use of older cessation studies which showed no effect – despite the obvious limitation. In particular, they often use studies where no comparison community was included and ignore completely the other factors involved such as changes in dental health provisions or social health policies such as replacing fluoridation with mouth rinse campaigns.

It is, therefore, ironic for them to come out fighting in an attempt to discredit a study which has fewer limitations than the ones they rely on. Worse, to accuse researchers of purposely omitting data – or even of scientific fraud.

The real reason for these attacks on honest researchers is that the data just does not fit the anti-fluoridation agenda and therefore, in their eyes, must be discredited.

Oh, and beware of such activists using the word “independent’ to describe a researcher. It inevitably indicates someone with allegiances to their campaign. Someone who can be relied on to give the appropriate quote to be used in their press releases.

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10 responses to “Anti-fluoridationist’s flawed attacks on Calgary study

  1. I guess I wouldn’t be labelled “independent” by the anti-fluoridationists, either.

    After all, I’ve never been a dentist, never worked in public health, never done research related to fluoride… If I see someone with dental problems (not an infrequent occurrence) I refer them to a dentist of their own choice.

    Unfortunately, I went to a medical school and am now being employed by a DHB. I suspect that both of those would disqualify my independence in the view of anti-fluoridationists.

    In reality, I was a “shruggy” over fluoride a couple of years ago. Some inane (my spellchecker wants to say insane!) comments from anti-fluoridationists, that seemed to pay no attention to chemistry, physics or biology, got me re-reading the texts on fluoride, and then more recent literature.

    You could say that the anti-fluoridationists have made me the pro-fluoridationist that I am. And all because they made so many inane/insane comments.


  2. Thanks, Ken. The FAN minions have predictably begun spewing Sheldon’s opinions on Calgary all over the internet. It’s truly a shame to see someone such as Sheldon so damage his credibility by aligning himself with the dubious antifluoridationist faction FAN.

    Steven D. Slott, DDS


  3. Of course the Kens and Stevens of this world fail to see that what Ken writes can be turned on its head and apply to themselves as well.
    The real reason for these attacks on anti fluoridation researchers is that the data just does not fit the pro-fluoridation agenda and therefore, in their eyes, must be discredited.
    Oh, and beware of pro F activists using the word “independent’ to describe a researcher. It inevitably indicates someone with allegiances to their campaign. Someone who can be relied on to give the appropriate quote to be used in their vitriolic comments.


  4. Trev – the attacks, misrepresentation of the research and accusation of neglecting or hiding data – together with claims of scientific fraud by your organisation FFNZ, are coming from the anti-fluoride propagandists. Not the science side.

    And it is the anti-science side who wheel pout people they call “independent” even they are often on the FAB board!

    Proscience people do not usually use that term because it is misleading. They rest their arguments and case on the evidence.


  5. Late to the party here – and haven’t read the FAN stuff. But I do have to say that I’m not sure this is a fair assessment. The main problem isn’t the study itself, but the way the media jumped on it; most outlets used it to write off anti-fluoride people as crazy crackpots, criticize Calgary politicians for getting rid of fluoride, etc. The reality is that the study (and yes, I have read it) is pretty far from being that damning of Calgary’s fluoridation policies, and it brings up a lot of questions which the media (and to a degree, the study’s authors themselves) don’t really go into.

    The big one is that, as you mentioned, Edmonton’s decay rates also went up, just not as much as in Calgary – why? At most, you could really only say that about 1.7% of the change could possibly be due to fluoridation – being similar cities, if Edmonton’s rate goes up by 2.1%, and Calgary’s by 3.8%, and the only noted difference is the fluoridation, then what’s causing the increase in Edmonton? And is it possible, then, that the other 1.7% could be due to things besides fluoridation as well?

    Also, re: the “missing” 2009/10 data, one has to admit that it’s odd that in the paper in question, they say that there was no data nearer to the cessation date than 2004/05, yet they published another paper on fluoridation in Calgary using 2009/10 data. I’m not implying it’s dishonest in any way, but it is very odd, and it’s easy to see why it’d be a cause for concern regarding the integrity and usefulness of these studies.

    It’s also interesting to note that they found a decrease in cavities in permanent teeth relative to Edmonton, and they said themselves that generally, studies show that the impact of fluoridation on dental health is inconsistent and likely highly dependent on other factors. They assert that damage to permanent teeth will probably happen, and state a slight increasing trend in narrowed subject groups as a sign of this, even though they say themselves that this trend is statistically insignificant. It’s easy to see the overall outcome of as equivocal at best.

    Myself, you could say I’m a bit of a “shrugger” on this one – I’m not too sure what I think of water fluoridation in general. However, I’m very strongly against the media reporting opinion pieces that gloss over issues in the study in favour of using it to promote one idea (and for some, calling people who disagree “crackpot conspiracy theorists”). No matter what you think about fluoridation, that’s just not excusable in journalism, and I wish more people would talk about the real findings of the study in more objective terms… but then I guess objective journalism has been dying for ages in favour of partially-informed opinion pieces and name calling, hasn’t it?


  6. Firefly – you say my article is not a fair assessment and that the main problem is the way the media have treated the study:

    “most outlets used it to write off anti-fluoride people as crazy crackpots, criticize Calgary politicians for getting rid of fluoride, etc.”

    So how have I contributed to that? I have simply dealt with the misrepresentation of the study by FAN (which you admit to not reading). I have no talked about crazy crackpots – I have dealt with the dishonest of the FAN article and substantiated my charges.

    So your claim my assessment was unfair for these reasons is invalid.

    I think you have confused defs with something else. In fact, defs increased by 146% in Calgary and 47% in Edmonton. (Work it out).

    All sorts of factors could be involved in the increase seen in Edmonton and that is the major reason for using a control city. The assumption is that other factors besides fluoride that causing a change will be operating in both cities so use of a control helps remove those factors. Sure, there could be factors operating differently in each city – but the use of control helps minimise this.

    You cast doubt on their reasons for not including data for 2009/2010 and your quote marks around “missing” seems to suggest dishonesty on their part – despite your assurance that you don’t imply dishonesty.

    You say it is “very odd.” Why is it odd? If tooth surface level data were not taken in 2009/2010 in Calgary then it wasn’t. That is what the real world is like.

    You do not say which paper they used the 2009/2010 data in. I can only surmise it was their paper on tooth level data – rather than tooth surface level data. The whole point about using tooth surface level data was to take advantage of the increased sensitivity.

    I think all this was made clear in the paper so I think you have perhaps approached it with some bias which prevented you from seeing the difference between tooth level and tooth surface level.

    So, I suggest you go back and read the paper more carefully.

    Your complaint about journalism is irrelevant here as I try not to indulge in name-calling (although I get some pretty extreme name-calling directed at me – accused of being a pedophile, purposely misspelling my name, claims I am a shill and paid by big business.

    I also am concerned about poor journalism on lots of issues. But I think your complaints would have been better directed at the anti-fluoride activists who misrepresented this paper and even made unwarranted charges against the authors. I referred to their shaming by association in their charge “The lead author of the study, Lindsay McLaren, is not an independent scientist on the fluoridation controversy.”

    Yet you seem completely unconcerned about such unethical behavior?


  7. Fair enough. It seemed as though some of the comments levelled at FAN were similar to some that I had read in the media about criticisms of the study in general, and you do later talk about anti-fluoridation activists in general, which is why I commented.

    I’m glad you also care about journalistic integrity. I do suppose McLaren is as independent as any other scientist, but she *is* on the Alberta Health Services’ Community Water Fluoridation committee, & did some fluoridation lobbying to the province, so I think I can forgive them for being skeptical of whether she’s overstating the effects of fluoride as the causal link here. Again, not saying they’re necessarily correct in thinking she’s biased, and they’re probably going too far in saying that she’s not independent – but it’s also not unreasonable or unethical to think she might be too biased in her interpretation of their results.

    Honestly, the only bias I have is that I’ve seen my share of studies where the results given are not anywhere near as certain or significant as the study authors or the media claim them to be, or that studies on basically the same thing can have radically different outcomes… not on this issue per se, since I only follow intermittently – but I’m an anthropologist and have seen it in my field on too many occasions to count, so I view most scientific findings with a certain amount of skepticism and room for error regardless of the position they take. I’ve seen “solid, indisputable science” corrected, overturned, misrepresented, overstated, and sometimes have serious design flaws that get hand-waved away…. and all of it is seen as unquestionably right until they find out it was wrong. So yeah, I come at things with a large dose of skepticism and try to view it from different angles. It’s in my training, I guess. I don’t have an anti-fluoridation bias; as long as it’s not damaging my health, I don’t really care one way or the other. I just like to make sure I have an accurate view of an issue and noticed most of the coverage of this is very biased.

    Actually, I had put “missing” in quotations because of the uncertainty that it was in fact missing (as you said FAN had asserted). You’re right that I mistook the two different types of data as being the same – mistakes happen. It wasn’t due to some bias, just a regular old mistake.

    However, I do stand by my opinion that this study isn’t strong enough to say that Calgary’s fluoridation policies are somehow deeply flawed – at best, it’s worth doing a bit more research and reviewing. Comparing the 2 cities, when both were fluoridated, Edmonton had a much higher rate of defs than Calgary, with the difference between the two in 04/05 being roughly as large as the difference in the increase in defs found in 13/14 – you can correct me if I’m wrong, but I don’t recall that being addressed in the article. I just find it a bit curious to say that the increase in Calgary is due to lack of fluoridation when such a large difference existed even when the two similar cities were both fluoridated.

    And I think I get what you’re saying with regards to the tooth-level data not being the same as the surface-level, and so you can’t use that as a good approximation for what the decay levels might have been in 09/10. Fair enough. That said, while we shouldn’t make direct comparisons, there’s no reason not to think about it in context of the larger picture.

    Claims that you can’t pinpoint whether the most increase happened before or after cessation are fair, since most of the time frame covered was pre-cessation. And it’s interesting that in the study using 09/10 data, they suggest that part of the increase is due to the fact that poorer people were found to not brush or use fluoridated toothpaste as often, yet in the study using 04/05 data, they gloss over the fact that both Edmonton and Calgary have seen an increase in unemployment, job instability, and cost of living over the years.

    Again, not necessarily saying FAN’s claims are all amazingly accurate or unbiased, but it’s fair to think this study’s not saying as much as pro-fluoridation people claim it is.


  8. Firefly, you say “It seemed as though some of the comments leveled at FAN were similar to some that I had read in the media about criticisms of the study in general.“ Could you be specific? What specific criticism of mine are you objecting to?
    Regarding bias – this is a normal human emotion. We all suffer from it. The great thing about science, though, is the reliance of objective facts and logic. And then the reliance on the critical and intelligent response of the scientific community.

    You have made some criticisms of the paper – good. Unfortunately, your criticisms were mistaken (for example you conflated tooth level and tooth surface level analysis). Also, these sort of mistakes are inevitable as critics also have their biases. But you have acknowledged your mistakes. Also Good.

    Now, I suggest you do what I have done throughout my articles. Subject the claims and research of the anti-fluid people to the same intelligent and critical analysis. For example, do you think the reliance of FAN on the work of Choi et al (2012) is unbiased or honest? Do you think that review of poor quality papers from areas of endemic fluorosis is at all relevant to community water fluoridation in the US or NZ? Do you think the hypothyroidism paper of Peckham et al (2015) was scientifically respectable? And what about the paper of Malin and Till (2015) on ADHD and fluoride?

    If you are not familiar with these papers (or their promotion by anti-fluoride propagandists, have a search here for articles I have written on them.

    In my analyses of these papers I have tried to explain their scientific faults – that is, rely on analysis of the data and highlight mistakes in procedure, statistics, etc. I think that this perfectly acceptable and normal in science.
    You say:

    “I come at things with a large dose of skepticism and try to view it from different angles. It’s in my training, I guess. I don’t have an anti-fluoridation bias; as long as it’s not damaging my health, I don’t really care one way or the other. I just like to make sure I have an accurate view of an issue and noticed most of the coverage of this is very biased.”

    Good, in theory – it is also my own approach and is consistent with experience in scientific research. But I will believe it when I see it applied properly (which you did not do with the Calgary paper) and, in the case of fluoridation, to a wider set of papers.

    The current understanding of community water fluoridation, its safety and effectiveness, is not based on a single study. It is a consensus based on all the research.

    I find that anti-fluoride activists are continually cherry-picking individual studies they claim shows harm or lack of effectiveness (and often they are incorrect). And then they reject the current consensus by claiming bias, industry finance, etc.

    Finally, decisions of specific actions like Calgary rely on more than individual studies. There is the whole field, many studies throughout the world showing the beneficial effects of community water fluoridation. And individual, local studies can only use the data available (and it is silly to write off a study because it relies on real-life existing data – with their inevitable faults – like this, rather than an imagined experimental setup).

    The decisions are also political – I fact science usually plays very little role in such decisions. And that is a problem with community water fluoridation – the decisions are being made by people who do not have the scientific expertise, have political ambitions and motives, and are being bombarded with propaganda from anti-science people who are well known for misrepresenting and distorting the science.


  9. Firefly, one of the reasons I suspect you of at least some degree of bias is that you are critical that some unspecified “pro-fluoride” people are claiming more for the study that is justified (and yet did not provide one example) but you are completely OK with the anti-fluoride claims that the study is “Fataly Flawed” and is “basically a fraud.”

    I find that surprising because the purpose of my article was to debunk these claims by explaining the study and showing where Sheldon, FAN and FFNZ were wrong.

    Incidentally, while I was able to correspond with Sheldon, neither FAN or FFNZ will allow me to contribute any discussion n 0on the websites or facebook pages they control.


  10. Pingback: Flaw and porkie in anti-fluoride report claiming a flaw in Canadian study – The Science Page

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