Tag Archives: thyroid

Anti-fluoride activists misrepresent another thyroid study

Image credit: Hypothyroidism | Natural Approach To Low Thyroid Hormone

Anti-fluoride activists closely follow the publication of results from fluoride studies and react to new scientific papers in one of the following ways:

  1. Use it to claim community water fluoridation (CWF) is harmful – even if this requires misrepresentation or distortion of the studies findings (a recent example is the prenatal fluoride/child IQ study of Bashash et al., (2017)  heavily promoted and misrepresented by Paul Connett in his current New Zealand talks).
  2. Viciously attack the study if it finds CWF beneficial and reports no harmful effects (remember their reaction to the NZ IQ-Fluoridation study of Broadbent et al., 2014).
  3. Do their best to ignore the study if it can’t be misrepresented and the media is not reporting it.

Well, now we have a very new study from Iran reporting relationships between drinking water fluoride and thyroid problems and already we can see activists launching into reaction 1.

The paper is:

Kheradpisheh, Z., Mirzaei, M., Mahvi, A. H., Mokhtari, M., Azizi, R., Fallahzadeh, H., & Ehrampoush, M. H. (2018). Impact of Drinking Water Fluoride on Human Thyroid Hormones: A Case-Control Study. Scientific Reports, 8(1), 2674.

So what did this study find? The paper itself is a little difficult to read but here is what I got from it.

No effect of drinking water fluoride on hypothyroidism

The study investigated two groups (“cases” – which had hypothyroidism and “controls” – which did not have hypothyroidism) and two drinking water fluoride concentration ranges ( 0 – 0.29 mg/L and 0.3 – 0.5 mg/L). To quote the findings:

“The frequency distribution of hypothyroidism based on the different levels of fluoride in drinking water was not significant for the cases (P = 0.13) and controls (P = 0.21) in YGA.”

And:

“At a concentration of below 0.5 mg/L, however, it [fluoride] is not an important factor for hypothyroidism in YGA.”

YGA is the “Yazd Greater Area . . . located in the Yazd province of Iran, which uses groundwater as the primary water source.”

So, no association found between hypothyroidism and drinking water fluoride. Yet, the Irish anti-fluoride guru, Declan Waugh, reported on Facebook

“the current study Published in Nature this past week, found that fluoride in drinking water, at levels below those present in tap water in Ireland, may contribute to thyroid impairment and a worsening of thyroid conditions in adults. In other words fluoride can contributed to sub-clinical and clinical hypothyroidism”

To avoid confusion, Waugh is referring to this study. Scientific Reports is a Nature journal.

So Waugh is citing a study which reported no statistically significant effect of fluoride concentration on the prevalence of hypothyroidism to claim “that fluoride in drinking water, at levels below those present in tap water in Ireland, may contribute to thyroid impairment and a worsening of thyroid conditions in adults!”

Incidentally, I do try to follow anti-fluoride activists on social media but did not see this myself as Declan Waugh blocks me. This was brought to my attention by a colleague who was probably more concerned about Waugh’s resorting to blaming homosexuality on fluoride – see the image of Waugh’s Facebook post. Citation dredging of the sort Waugh indulges in certainly makes one susceptible to these sort of claims – especially if they “confirm” a bias.

The study is already being used by groups like UK Against Fluoridation and Fluoride Free NZ who cite the paper as evidence of harm – but seem not to understand the paper and simply quote sections dealing with thyroid hormones and not the findings on the lack of effects on hypothyroidism prevalence.

Thyroid hormones

The study did report statistically significant differences in hormone levels.

I am not an endocrinologist so will not get into a discussion of what these changes might mean. Here I will simply present them and compare them with hormone levels considered normal.

The authors investigated the T4, T3 and TSH hormones.

No significant fluoride effects occurred with the T4 hormone.

A very small effect occurred for the T3 levels in the control group (no hypothyroidism present) – the authors claimed this was statistically significant but I find that hard to believe – see Figure.

The T3 hormone levels were within the normal range (yellow area) for both groups. It’s not surprising to see different levels in the hypothyroidism cases. But drinking water fluoride has no significant effect there (p=0.19) – and I am picking the claim of a statistically significant effect (p=0.026) on the control group is wrong.

The authors claimed significant differences of TSH hormone with fluoride concentration for both the control and hypothyroidism groups – see Figure.

The TSH levels for the control group was in the normal range (yellow area) and the difference (although statistically significant, p=0.001) was extremely small. The levels for the hypothyroidism cases were outside the normal range – probably as a result of hypothyroidism. Again, I wonder at the claimed statistically significant effect (p=0.003) of fluoride for the hypothyroidism cases.

Other risk-modifying factors

While hypothyroidism prevalence was not significantly related to fluoride concentration the study reported that it was related to gender, family history of thyroid disease, water consumption, exercise, diabetes, and hypertension.

The authors note that “patients with hypothyroidism . . .  have a higher consumption of drinking water.” So this association probably means increased water consumption is a result of hypothyroidism and not a cause of it.

Some misleading comments in  the paper

The authors seem to have an anti-fluoride bias, and I wonder at studies which demonstrate statistically significant relationship for a range of risk-modifying facts, but not for fluoride, yet still concentrate on possible fluoride effects. Particularly at such low fluoride concentrations.

For example, the authors say:

“we obtained an unadjusted OR of about 1.034 (CI 95%: 0.7–1.53) for fluoride in drinking water when its concentration was less than the standard (0.2–0.5 mg/L). This finding is consistent with the Peckham study in England, which reported OR = 1.5 (CI 95%: 1.16–2) for hypothyroidism, where the maximum fluoride concentration was more than 0.7 mg/L.”

That is just special pleading – trying to “save” a non-significant result. And special pleading to compare it with the Peckham study which has been roundly criticised for not considering the effects of iodine deficiency which is known to be a major contributor to hypothyroidism.

And another case of special pleading is this:

“TSH values are higher (in both cases and controls) with higher levels of water consumption. This is consistent with an association between increased fluoride intake (due to increased water consumption) and increased TSH.”

They have turned this water consumption on its head – now ignoring that it is caused by hypothyroidism (patients drink more water) and claiming the TSH changes are a result of increased fluoride intake. This is simply an attempt to overcome the lack of any statistically significant effect due to fluoride levels in drinking water by postulating there is really an effect because of increased water consumption by hypothyroidism patients.

Conclusion

I do not think this is a good paper. Decent peer review could have improved it – and hopefully removed the obvious bias and special pleading of the authors.
It cannot honestly be used to claim fluoridation causes hypothyroidism – as anti-fluoride campaigners will do. However, activists will dredge out quotes from this paper which will be used to give an impression of results actually not present in the paper (fluoridation causing hypothyroidism).

So a paper which actually doesn’t support anti-fluoride claims – but can easily be misrepresented to fool the uncritical reader.

Similar articles

More nails in the coffin of the anti-fluoridation myths around IQ and hypothyroidism

thyroid_fluoride

Large Canadian study finds no effect of fluoridation on thyroid health

A new Canadian study shows no relationship of cognitive deficits or diagnosis of hypothyroidism with fluoride in drinking water. This work is important because it counters the claims made by anti-fluoride campaigners. While the campaigners cite scientific studies to support their claims, those studies are usually very weak, or irrelevant because they involve areas of endemic fluorosis where drinking water fluoride concentrations are much higher than in situations where community water fluoridation (CWF) is used.

The study is reported in:

Barberio, A. M. (2016). A Canadian Population-based Study of the Relationship between Fluoride Exposure and Indicators of Cognitive and Thyroid Functioning; Implications for Community Water Fluoridation. MSc Thesis, University of Calgary

This new study is important as it has the advantages of using a large representative sample of the Canadian population, with extensive data validation and quality control measures. It also uses individual-level estimates of fluoride exposure on the one hand, and thyroid health and cognitive problems on the other.

Fluoride exposure was measured both by concentration in tap water for selected households and concentration in urine samples from individuals.

Thyroid health

The Canadian study found:

“Fluoride exposure (from urine and tap water) was not associated with impaired thyroid functioning, as measured by self-reported diagnosis of a thyroid condition or abnormal TSH level.”

This contradicts the conclusions from the population-level study of Peckham et al., (2015) which reported that fluoridation was correlated with the prevalence of hypothyroidism. That study is quoted extensively by anti-fluoridation activists but has been roundly criticised because it did not include the influence of confounders – particularly iodine which is known to influence thyroid health.

Barberio (2016) also suggests that the different recommended fluoride concentrations used for CWF in Canada and the UK, and the fact that the Peckham et al (2015) study did not involve individual measures, could also be factors in the different findings.

Cognitive functioning

The Canadian study reported:

“Fluoride exposure (from urine and tap water) was not associated with self-reported diagnosis of a learning disability.”

Barberio (2016) did also investigate a more detailed diagnosis for cognitive problems and found:

“Higher urinary fluoride was associated with having ‘some’ compared to ‘no’ cognitive problems . . . . however, this association:

  • Was weak;

  • Was not dose-response in nature; and

  • Disappeared when the sample was constrained to those for whom we could discern fluoride exposure from drinking water.”

I guess anti-fluoride activists might latch on to this last point regarding urinary fluoride but, at least as far as tap water fluoride is concerned, there was no relationship with learning difficulties.

Conclusion

So – yet another large-scale study contradicts anti-fluoridationist claims. It shows that CWF has no influence on cognitive problems or thyroid health.

Similar articles

Paper claiming water fluoridation linked to hypothyroidism slammed by experts

“As epidemiological evidence goes, this is about as weak as it gets.”

Author Stephen Peckham – former chairperson of activist group “Hampshire against fluoridation”

That is the comment by Prof David Coggon, Professor of Occupational and Environmental Medicine, University of Southampton, on a new paper claiming hyporthyroidism is linked to water fluoridation. Published yesterday in the peer-reviewed Journal of Epidemiology & Community Health, the paper is:

Peckham, S., Lowery, D., & Spencer, S. (2015). Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water. J Epidemiol Community Health, 1–6.

Prof Coggan goes on to say:

“Essentially the researchers have shown that after limited adjustment for demographic differences, there are somewhat higher rates of hypothyroidism (which can result from a number of different diseases) in four areas of England that have higher concentrations of fluoride in drinking water.   It is quite possible that the observed association is a consequence of other ways in which the areas with higher fluoride differ from the rest of the country.  There are substantially more rigorous epidemiological methods by which the research team could have tested their idea”

Having read the paper I think that about sums it up.

Critical role of iodine.

The authors acknowledge that iodine plays a key role in thyroid status but they did nothing to include dietary intake or deficiency in their statistical model. It is just not good enough to declare “it is unlikely that there are significant differences [in dietary iodine intake] between people, living in fluoridated and non-fluoridated areas.”

They did include data for the proportion of people over 40 and the proportion of females because they recognised age and gender influence the incidence of hyperthyroidism. So why not include dietary iodine which is recognised as the main factor? And they are arguing that fluoride potentially acts as an iodine inhibitor, making the data for iodine even more important. Perhaps this data was not so easy to find – but did they look very hard?

Correlation is not causation

This cannot be repeated often enough. Trouble is that almost anyone can get hold of data these days and force it through a statistical package. And if they have a bias to confirm, and are willing to select their data and avoid confounders, they might get lucky.

This seems to be the case here as the senior author is a well-known anti-fluoride campaigner in the UK.* This is outside his specialty (health policy, not epidemiology).

Fluoridation data is readily available for cities and regions but it can easily be a proxy for more meaningful information like the size of towns (smaller towns usually don’t have artificially fluoridated water) or rural/urban distinctions. Cultural and ethnic factors may also be reflected in fluoridation data.

In this case, Peckham et al., (2015) simply correlated the incidence of hypothyroidism reported by individual medical practices against drinking water fluoride concentrations reported by local bodies in the region. There was no attempt to match data at the individual level. And there was no attempt to include dietary iodine intake as a factor – despite its key importance.

The size of the effect

The prevalence of hypothyroidism in the data they used is relatively low  – 3.2% with a standard deviation of 1.1%. The authors argue their results would mean that fluoridation would increase this small number by a small amount (about 30%).

Given the tentative nature and unreliability of their conclusions – if only because they did not consider dietary iodine as a factor – their recommendation should be taken with a grain of salt (preferably iodised). They recommend:

“To minimise the risk of increasing the prevalence of hypothyroidism, it is important, therefore, to limit fluoride ingestion from all sources.”

Sensible health authorities will balance the low incidence of hypothyroidism and the small effect Peckham et al (2015) claim, based on their unsatisfactory analyses, against the fact of the beneficial role that fluoride plays in the oral health of most people throughout their lives

Obviously authorities are no going to change their views as a result of this paper. Of course there will be special pleading by those opposed to fluoridation. They will argue that despite the problems with this paper the questions of fluoride as a factor in hyperthyroidism should be research further. Of course it should – scientific conclusions are always open to being altered by new evidence. But future research must be of a better quality than this. As a Prof Coggan says:

“There are substantially more rigorous epidemiological methods by which the research team could have tested their idea”

Stephen Peckham is a well-known anti-fluoride activist

I discussed Stephen Peckham in a earlier article Peer review, shonky journals and misrepresenting fluoride science. This deals with a previous paper of his and the journal he published it in.

That paper was a collection of the usual anti-fluoride arguments – based in citations without any original work. It was published in a shonky journal known to have poor peer review standards.

The current paper is in a reputable journal and does include some original work – although it is basically a statistical analysis of readily available data. No effort seems to have been made to include data for dietary iodine intake which I would think is a basic need for such a study. I am personally surprised the reviewers used by this journal did not seriously question the paper’s publication for that reason alone. I guess this reflects the imperfect and human nature of peer review even in good science journals.

At least with the current paper Stephen Peckham has declared  a conflict of interest involving his activity opposing water fluoridation – this did not happen with his earlier paper.

I expect this new paper will become another weapon in the anti-fluoridation artist armoury. It will be cited and presented as absolute proof that fluoridation is bad for our thyroids. Claims will be made that a leading scientific journal and university officially claim this! Harvard University and The Lancet all over again.

But sensible readers should never take such claims at face value. Just because a paper is published in a reputable peer-reviewed journal does not make it gospel truth. Whatever the source, such papers need to be considered intelligently and critically.

This paper does not live up to the claims the anti-fluoride propagandists will make about it.

See also:

Flawed study overstates link between fluoride and ill health: experts
Tournage de la scène «Fluoration de l’eau», prise 2793… (Shooting the scene “Water fluoridation,” taken in 2793)

Similar articles