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a tale of rare blood groups, or, ‘the man with the golden blood’ Alison Campbell Nov 03

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One of the topics we cover in first-year biology is human blood groups – it’s discussed during genetics classes & also touched on when looking at how immune systems function. I give the genetics classes and, being a regular blood donor myself, thought I knew a bit about at least the common blood groups and their inheritance. But there’s always more to learn, something I was reminded of when I read a fascinating story about people with truly rare blood types: “The man with the golden blood”.

There’s ‘Thomas’, for example: a man who lacks the Rhesus markers completely & so is classified as Rhnull  - in 2010 he was one of an exclusive global club of 43 individuals (of whom only 6 regularly donate their blood). And James, who is ‘Lutheran b negative’, and one of only 550 active donors for this blood type.

This makes known donors precious, in that if someone else with the same group needs a blood transfusion, there are very very few people around the globe who might be able to help them. And helping comes at a cost to the donors, for – as the story tells us – it’s actually easier in many cases to move people across borders than it is to move blood, but because many countries don’t pay donors, then that movement may well be at the donor’s expense. It’s also difficult for people like ‘Thomas’, with his vanishingly rare blood group: his blood can be used by anyone who’s Rhesus negative, but he can receive blood only from another Rhnull person, which means he has to be reasonably careful not to put himself in harm’s way (although he does still go skiing!).

Quite an eye-opener – and a tale I’ll be including in next year’s class.

‘alternative’ medicine – numbers using it =/= evidence it works Alison Campbell Oct 26

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Recently some friends & I were discussing the use of what might be called ‘Supplementary, Complementary, & Alternative Medicine’ – a group of ‘therapies’ that includes (but is not limited to) things like homeopathy, reiki, acupuncture, ear candling, and cranio-sacral therapy, and for which there is little or no evidence of efficacy.

One of the reasons given by those supporting their use is a form of the ‘argument from popularity’ logical fallacy: ‘but look at how many people use them. They can’t all be wrong!’ That viewpoint is exemplified here, in the claim that a large number of doctors are now recommending alternative therapies to their patients, or providing these therapies themselves. The list offered at one such practice includes

psychologists, naturopaths, nutritionists, cranio osteopaths, massage therapists, hypnotherapists, yoga practitioners, an acupuncturist and a breast thermography technician.

Now, massage, yoga (exercise), and psychology are hardly ‘alternative’, although including them in the list then allows one to inflate the number of people supposedly seeking out alternative health modalities. Most of the rest have been addressed far better than I could by Orac (see here, for example, and here) and the authors of the Science-Based Medicine site.

But let’s not get distracted. As my friend Renee said: the claim is that lots of people use these modalities, therefore they must be good; a claim supposedly supported by “the impressive statistics showing people are now willing en mass [sic] to spend their dollars on integrated health care”. What we should be asking to see are the statistics showing the efficacy of such care, before we start spending any more of our scarce health dollars on it.

‘paleo’ diet? or paleofantasy? Alison Campbell Oct 17

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The ‘paleo’ diet story on Campbell Live tonight spurred me to finish my review of one of the most entertaining popular books on genetics that I have read for some time. Entertaining, and informative, in equal measure. I wonder what author Marlene Zuk would have made of the TV story.

book cover Marlene Zuk (2013) Paleofantasy: what evolution really tells us about sex,diet, and how we live.  Norton (New York)

ISBN 978-0-393-34792-0 (paperback)

For in that story we heard gems like this: “It’s a commitment to eating food that is unadulterated, eating food in its most natural state.” Paleo proponents (says the TV story) believe our most natural diet is that of our Palaeolithic cavemen ancestors. Somehow I doubt our ‘cavemen’ ancestors were eating avocados, beetroot, bacon or kale. (There’s also an air of chemophobia, with one proponent of paleo eating stating that their diet contains “[n]othing nasty and nothing you can’t pronounce” – which reminded me of the series of posters by Australian teacher James Kennedy, showing the list of chemical compounds found in natural food items: blueberries, anyone?).

Proponents of the so-called paleo diet seem to think that humans haven’t evolved in the last 10,000 years (since the advent of agriculture), and that this means that our bodies aren’t ‘designed’ to cope with the products of the agricultural revolution. (This, while eating foods that bear little resemblance to their Palaeolithic counterparts. Look at teosinte, the ancestor of maize, for example: small, stone-hard kernels arranged in a few lines on a stalk. Nothing like the fat, soft, juicy kernels on a modern cob of corn.)

As Zuk notes, the paleofantasy happily assumes that at some point in the past (around 10,000 to 40,000 years ago, depending on who you’re listening to), humans were perfectly adapted to their environment, including their diet. But, she asks, why hark back to that particular point in time?

would our cave-dwelling forebears have felt nostalga for the days before they were bipedal, when life was good and the trees were a comfort zone?

Plus, of course, there’s the question of just which ’cavemen’ we’re aspiring to be like. We’ve no guarantee that the life-styles of modern hunter-gatherer populations are a good approximation of life 40,000 years ago. Should we be Inuit, or Kung?

And there’s no reason for us to have stopped adapting to evolutionary pressures once agriculture became the mainstay of human populations – in fact, there’s a great deal of evidence to the contrary, some of which I’ve written about previously -the evolution of lactase tolerance, for example. Similarly, with the spread of arable farming, those with the ability to digest grains would be at an advantage, to the extent that there is a higher number of copies of the gene coding for salivary amylase in populations with a long history of eating starchy grains, compared to populations where the diet has traditionally been low in starches. And Zuk provides many examples of just how rapid evolutionary change can be, in humans and in other animals (changes in cane toad morphology, in the short span of time since their arrival in Australia, are a particularly elegant case in point). The final chapter, which gives considerable detail in answering the question, are we still evolving, would be very useful to biology teachers during human evolution classes.

In other words,

[t]he notion that humans got to a point in evolutionary history when their bodies were somehow in sync with the environment, and that some time later we went astray from those roots – whether because of the advent of agriculture, the invention of the bow and arrow, or the availability of the hamburger – reflects a misunderstanding of evolution.

As the extended title of her book points out, Zuk feels that the paleofantasy extends well beyond the current diet fad. It influences beliefs about health and illness, about family life, about sex. (This last is the focus of all sorts of wistful imaginings: the book provides an entertaining sample of these.) Do bonobos, for example, really provide a good model for how human sexual activity might have been before modern mores took over? I can’t see it myself: humans and their chimpanzee cousins have follwowed separate evolutionary trajectories for 5-6 million years, and there’s no good reason why either species should closely resemble the last common ancestor. And that goes for aspects of intimate morphology as much as for behaviour: I did not know that chimpanzees have penis spines –  ”hardened growths that may serve to sweep away the sperm of previous mates.”

Zuk concludes that the paleofantasy is just that, a fairy tale – and one that limits our understanding of our own biology and evolutionary history:

But to assume that we evolved until we reached a particular point and now are unlikely to change for the rest of history, or to view ourselves as relics hampered by a self-inflicted mismatch between our environment and our genes, is to miss out on some of the most exciting new developments in evolutionary biology.

 

Anyone interested in hearing Professor Zuk speak should check out the details of her upcoming lecture tour. I’ll be grabbing a ticket to the Hamilton event!

 

there’s the alarming news about ebola, & then there’s this Alison Campbell Aug 03

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Over on Sciblogs, Siouxsie Wiles has been writing about the spread of an Ebola virus outbreak in west Africa (here  here, for example). It’s alarming stuff: a virus with a high mortality rate, in combination with the potential for infected people to travel more widely than in the past before succumbing.

Sadly, it didn’t take long for the pedlars of pseudoscientific nonsense to get on the bandwagon. First it was homeopathy (apparently homeopathic concentrations of rattlesnake venom and other ‘remedies’ will do the trick – I wonder how they found that out?) In his blog post on this, Orac has commented

You know what they call an Ebola victim foolish enough to use these five homeopathic remedies in the hope of curing their disease? Almost certainly dead, that’s what!

Indeed.

And then there’s this. I should really give that page to my first-year bio students & see what they make of it: they’d certainly pick up on the author’s statement that our cells have walls! What’s more:

It’s impossible for a virus to live in the presence of pure, unadulterated cinnamon oil, so getting that oil into our bloodstreams to create an environment hostile to the virus is important.

Viruses are only active within living cells, and I’m fairly confident in saying that our own cells can’t live in “pure, unadulterated cinnamon oil” either. (I do want to know, though, why the author feels that one must anoint one’s feet with the stuff!)

However, the page does have references, and we’re urged to read them, so let’s look at those sources to see if they back up the claims being made for cinnamon oil. There are “13 studies on cinnamon oil and viruses” from PubMed, for example, as well as a couple of in vitro studies.

Well yes, yes, there are – but I doubt the page’s author actually read them, despite asking their readers to check the links. For several references of that PubMed list are for various studies that used LEC (Long-Evans Cinnamon) rats, while others are discussing avian flu in a range of waterfowl that includes cinnamon teal – nothing to do with using an essential oil against viruses! Of the remainder, one is a study of herbal medicines that include cinnamon bark (not oil); one looks at the efficacy of a range of traditional medicines (again, including cinnamon bark) on baculovirus in silkworms; two others look at using flavonoids (hint: not oils) from cinnamon as a potential drug in fighting HIV.

I will confess to being underwhelmed. And concerned that anyone might take this stuff seriously.

gmo myths & mythinformation Alison Campbell Jul 28

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The GMOLOL group on Facebook regularly posts on the subject of Genetically Modified Organisms (GMOs) and more recently – like many other pages – about the outrageous claims by the self-styled “Health Ranger” about Monsanto, likening the company & pretty much anyone with anything positive to say about GMOs to the Nazi regime of WWII. (NB he’s actually gone back & added a ‘preface’ to the original post at that link, due at least in part to the internet fuss that followed his original posting.) Fairly soon after another webpage posted names & details of scientists working on or speaking in favour of GMOs, which was unsurprisingly viewed as quite threatening by at least some of those named. There’s an interesting bit of forensic work on the 2 pages & the sequence in which they appeared here. And Orac has a thoughtful commentary here.

It was also not a surprise to see the Ranger using myth to make his case: claiming here, for example, that GMOs have led to widespread farmer suicides in India. No sense in letting the truth get in the way of a good story, I suppose. Especially when it turns out to be rather more complex.

Of course, he is ignoring the fact that we have been selecting for genetically modified organisms for at least as long as we’ve had agriculture and domesticated animals. Sweetcorn or watermelons, anyone? Let alone that horizontal gene transfer is an excellent mover of genes that can link widely separated taxonomic groups; this example of fungi using bacterial genes to form nodules on plant roots is a case in point.

I’m guessing he wouldn’t like the idea of GM insulin or using GM mosquitoes to control the spread of dengue fever, either.

The internet can be a fun place to play & to find information, but alas! it’s also made it so much easier to spread mythinformation to a much wider audience than ever before.

helicobacter pylori and the complexity of the human microbiome Alison Campbell Jul 24

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In their first-year microbiology lectures. our students hear about Helicobacter pylori, the bacterium associated with the development of gastric ulcers (a discovery that eventually saw Barry Marshall and Robin Warren receive the 2005 Nobel Prize for Physology or Medicine). The trouble is, I suspect that this is all that they hear about a story that is considerably more complex.

The story of H.pylori is just one part of Jessica Snyder Sach’s highly readable and thoroughly-referenced book, Good Germs, Bad Germs, which introduces the reader to the complexities of the human microbiome: the intricate microbial ecosystems found on and within the human body.

Good Germs, Bad Germs: health and survival in a bacterial world. Jessica Snyder Sachs (2008) pub. Hill & Wang. ISBN (e-book): 0809016427

The book begins with the harrowing tale of a young man’s death from a rampant MRSA infection, and of a child living with multiple life-threatening allergies.- two tales linked by the unforseen effects of our overuse of anitbiotics and our fixation on hygiene. (Actually, the former was not entirely unseen: in his 1945 Nobel Prize lecture, Alexander Fleming commented on the possibility that overuse of penicillin could see the development of resistant bacteria. Unfortunately, at the time this warning went unheeded – if indeed it was really heard – for example, penicillin was available as an over-the-counter drug in the US for almost a decade after its introduction in the 1950s, which would undoubtedly have contributed to the development of resistant strains of microbes.)

Then, after an introduction to the “war on germs” and scientists’ search for the ‘magic bullets’ that would (it was hoped) allow us to vanquish them forever, it’s on to “life on man”. Wherein I learned heaps, including the thought-provoking suggestion that there may be some adaptive significance to the fact that babies usually exit the vagina with their heads face backwards, towards the mother’s anus. For babies guts are colonised by bacteria very soon after birth – & they may receive an inoculum of faecal matter on the way out, to join the lactobacilli  from the vagina itself and bifiobacteria from breast milk.

Incidentally, while all this may sound uncomfortably germy, there’s good evidence that the gut microflora are essential for survival. Lab animals reared in absolutely germ-free conditions, & whose guts never develop a microbial flora, fail to thrive. What’s more, Snyder Sachs  comments that the combined acction of several species of intestinal bacteria “liberate as much as 30 percent of the calories a person absorbs from food, especially from high carbohydrate meals.”

Reading on – and it was really hard to put this book down! – you’ll hear about the hygiene hypothesis, which suggests that many of the inflammatory diseases that plague us today are an unforeseen result of lives that are too clean. Along with this is the ‘dirt vaccine’: the idea that vaccination with a mycoplasma may help to redirect the overzealous immune response underlying many allergies. Then it’s on to a deeper look at the development of antibiotic resistance and the rise of the superbugs, which has been exacerbated by the widespread use of antibiotics in farm animals. (Encouragingly, Snyder Sachs notes that banning this use, as in the Netherlands, can lead to a reduction in ‘superbug’ prevalence.) And finally, we look at our options for the future, and whether we can find a way to live in balance with our burgeoning microbial ecosystems.

And H.pylori? It turns out that this particular bacterium has been with us for at least 60,000 years, something that’s been used to track human migration patterns that began when Homo sapiens first left Africa. H.pylori colonises the stomach in the first few months of life, before gastric acid secretion really ramps up, and can actually affect that acid secretion, lowering the pH enough that Helicobacter can survive but most other species are killed. There is a plus to this: the lowered pH reduces the effects of acid reflux & the development of oesophageal cancer. But then, there’s those gastric ulcers – which apparently didn’t really become an issue until the 1830s, when this was mainly a disease of the upper classes, possibly linked to a decline in colonisation related to improved sanitation and the use of early antibiotic products. And gastric ulcers

remain virtually unknown in undeveloped regions of the world such as Africa, where most people become colonised in infancy. It may be that delaying or disrupting H.pylori colonisation with water sanitation or antibiotics has somehow altered the immunological ‘truce’ that this microbe forged with our immune systems over thousands, possibly millions, of years.

I like the full, more complex story; it’s so much more satisfying than the ‘helicobacter – bad’ version, and it’s a much better reflection of the dynamic relationship between humans and the microbes that call us home.

homeopathic first aid Alison Campbell Feb 23

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Some of my fellow Skeptics have been discussing a homeopath who offers courses in ‘homeopathic first-aid for the home’. Might work for dehydration, I suppose, given that a 30C dilution (that’s a 1 in 100 dilution, repeated 30 times) will have nothing in it but water… But I rather think that homeopathic arnica - recommended here for acute trauma! – would have been worse than useless the time that the Significant Other’s leg interacted with a heavy, sharp, falling object  – give me real-world first aid any day!

Mitchell & Webb said it all, really.
;

 

fluoridation in the news Alison Campbell Feb 04

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I didn’t intend to write another post on this subject so soon after the last one, but a story on yahoo.com’s news feed has really annoyed me. I know journalists these days are seriously under pressure, but that doesn’t really justify taking a ‘press release’ from a known activist organisation and running it uncritically ie without actually looking into any of the claims made therein. You’ll find the story here, & I’m going to comment on some of the claims it contains below. (I would have done it directly on the yahoo.com piece but they don’t actually allow comments, grumble grumble mutter.)

Dr Paul Connett is currently visiting NZ and Australia to promote the views of the anti-fluoridation organisation FAN and its antipodean sub-groups. While he has reportedly spent 17 years ‘researching’ issues associated with community water fluoridation (CWF), he has published neither original research papers on this particular topic nor a systematic review of the existing scientific literature, in leading science journals. He has, however, published a book on the subject, the contents of which formed the basis of an extensive discussion on the Open Parachute science blog (also syndicated to the Science Media Centre’s sciblogs.co.nz). This output doesn’t really justify the ‘expert’ description so adroitly promoted by the FANNZ spokesperson who provided the yahoo item.

Repeated calls for a ‘debate’ are rather misleading as they suggest that there is in fact something to debate. In the case of the science behind CWF, as Sir Peter Gluckman has said, it is effectively settled. To call for a debate is simply an attempt to sow doubt and fear in people’s minds, and any such event would be ‘won’ by the better demagogue and not necessarily on the basis of the actual science presented. Thus it makes perfect sense for TV3 to seek comment from Dr Jonathan Broadbent, who has a solid research record around oral health, rather than to opt for the flawed ‘debate’ format & so give some feeling of false equivalency to an issue where none exists.

The FANNZ claim that our health officials are “[advocating] a highly toxic chemical be added to the drinking water of over 2 million people” is an attempt to imply that this practice is doing harm. However, there is no good evidence that the fluoridated water coming from the taps actually causes significant adverse health effects. Nor have health officicals “gone into hiding” (as stated in the yahoo story), as Dr Broadbent’s willingness to be interviewed clearly demonstrates,

What are the facts that FANNZ is so keen for New Zealanders to hear? The organisation certainly seems keen to obscure the evidence that community water fluoridation improves oral health (here, here, and here, for example) and is a cost-effective way of doing so. The spokesperson comments that it “is [health officials'] responsibility to provide people with real factual information” – and appears to be ignoring the fact that the National Fluoride Information Service has been set up to do just that. And just today dental health experts have provided commentary on fluoridation via the Science Media Centre.

As I’ve said, many large-scale systematic reviews have found that there is good evidence that ingesting fluoride reduces decay – and, contrary to the claim in the original press release – the evidence of “unacceptable health risks” is not “growing daily”. For example, the claim that fluoride is implicated in development of osteosarcoma appears to be based on a single preliminary study, and is not supported by more recent large-scale analyses. Similarly the ‘Harvard’ review, often cited as evidence that fluoridation affects IQ, has a number of flaws, some of which were identified by the authors themselves.

Yahoo.com, it’s a real pity you didn’t look into this one rather more deeply.

fluoride-cancer claims exaggerated? it looks that way Alison Campbell Feb 03

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My friend & blog-buddy Grant drew my attention to a story about osteosarcoma at stuff.co.nz – and to the comments section, where one commenter raised the issue of a claimed link between this rare form of cancer and community water fluoridation (CWF). This particular claim has surfaced quite a lot lately, as anti-fluoride groups target various local body councils around the country.

The claim is based on a published PhD study by Bassin (Bassin et al. 2006), who looked at a sample of 103 children with osteosarcoma and 215 matched controls, and concluded that there was a link between exposure to fluoride and the development of osteosarcoma in boys, but not in girls. They also noted that the findings were preliminary and needed further study, preferably involving biomarkers eg fluoride levels in bone. (Thus it’s interesting, to say the least, that this study is promoted so definitively by those opposed to CWF.) And in fact there have been a number of further studies – none of which support the Bassin group’s findings.

For example, in 2011 Kim et al published the results of a case-control study of 137 osteosarcoma patients and 51 controls. They measured the amount of fluoride present in the bones of patients and control individuals (in this case, patients with other forms of cancer), made allowances for age (& thus duration of exposure to fluoride in drinking water) and gender. The team used the bone assay because, since “fluoride has an affiinity for calcified tissues” (ibid.), levels in the bone are a more reliable, objective measure of fluoride exposure than measurements based on residential history or – in the case of the paper by Bassin et al – interviews with patients about their use of fluoridated mouthwashes & supplements, in addition to information on where they’d lived.

The team found there was

no significant difference in bone fluoride levels between cases and controls

and concluded that

[n]o significant association between bone fluoride levels and osteosarcoma risk was detected in our case-control study, based on controls with other tumor diagnoses.

They also characterised Bassin’s study as ‘exploratory’ and noted that a large number of earlier animal studies, and descriptive and case-control studies in humans, had not found any association between osteosarcoma & fluoride exposure.

<EDIT Feb 4> Also in 2011, Comber & colleagues compared osteosarcoma in Northern Ireland and the Republic of Ireland. While anti-fluoride groups regularly claim that osteosarcoma rates are higher in the Republic of Ireland, where water is fluoridated, and lower in Northern Ireland where CWF has never been implemented, Comber et al found no evidence for such an association:

The results of this study do not support the hypothesis that osteosarcoma incidence in the island of Ireland is significantly related to public water fluoridation.

Note that they did add a caveat, related to their small sample size:

this conclusion must be qualified, in view of the relative rarity of the cancer and the correspondingly wide confidence intervals of the risk estimates.

However, subsequent studies have borne out their results. </EDIT>

Again, in 2012 Levy and Leclerc used information covering the period 1999-2006 from the Centres for Disease Control database to probe the supposed link between CWF and this form of cancer. This was a weaker study than that of Kim’s team, because it used the proportion of a state’s population exposed to CWF as the proxy for fluoride exposure, but it concluded that

the water fluoridation status in the continental U.S. has no influence on osteosarcoma incidence rates during childhood and adolescence.

Most recently, Blakey and colleagues (2014) studied more than 4,000 patients with either osteosarcoma (N = 2566) or Ewings sarcoma (N = 1650), with the aim of their study being

to examine whether increased risk of primary bone cancer was associated with living in areas with higher concentrations of fluoride in drinking water.

Their conclusions?

The findings from this study provide no evidence that higher levels of fluoride (whether natural or artificial) in drinking water in [Great Britain] lead to greater risk of either osteosarcoma or Ewing sarcoma.

In other words, to date the further research Bassin’s team called for has not replicated their findings, and means that claims of a causal link are questionable at best.

<EDIT Feb 4> NB The New Zealand National Fluoridation Information Service also has some excellent information around this issue, including an analysis of data from the national cancer registry which again suggests no link between CWF and osteosarcoma.</EDIT>

E.B.Bassin, D.Wypij, R.B.Davis, M.A.Mittleman (2006) Age-specific fluoride exposure in drinking water and osteosarcoma (United States). Cancer Causes Control 2006(17): 421-428

K.Blakey, R.B.Feltbower, R.C.Parslow, P.W.James, B.G.Pozo, C.Stiller, T.J.Vincent, P.Normal, P.A.McKinney, M.F.Murphy, A.W.Craft, & R.J.Q.McNally (2014) Is fluoride a risk factor for bone cancer? Small area analysis of osteosarcoma and Ewing sarcoma diagnosed among 0-49-year-olds in Great Britain, 1980-2005. Int.J.Epidemiol, doi: 10.1093/ije/dyt259. First published online: January 14, 2014.

H.Comber, S.Deady, E.Montgomery & A.Gavin (2011) Drinking water fluoridation and osteosarcoma incidence on the island of Ireland. Cancer Causes Control 22(6): 919-924. doi: 10.1007/s10552-011-9765-0

F.M.Kim, C.Hayes, P.L.Williams, G.M.Whitford, K.J.Joshipura, R.N.Hoover, C.W.Douglass, & the National Osteosarcoma Etiology Group (2011) An assessment of bone fluoride and osteosarcoma. J.Dent.Res. 90(10): 1171-1176. doi: 10.1177/0022034511418828, PMCID: PMC3173011

M.Levy & B.S.Leclerc (2012) Fluoride in drinking water and osteosarcoma incidence rates in the continental United States among children and adolescents. Cancer Epidemiol. 36(2): e83-88. doi: 10.1016/j.canep.2011.11.008. Epub 2011 Dec 19.

the science-based medicine blog on fluoridation Alison Campbell Jan 22

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This is something that I posted on Making Sense of Fluoride, but thought I’d re-post here; it deserves to be widely read. I’ve highlighted some of the main points made by the authors as they address issues frequently raised by those opposed to community water fluoridation.

The Science-Based Medicine blog is an excellent resource and well-worth adding to your regular reading list. A few days ago Clay Jones (a paediatric hospitalist) & Grant Ritchey (DDS) posted an article entitled “Preventing Tooth Decay in Kids: Fluoride and the Role of Non-Dentist Health Care Providers“. It’s reasonably long but contains a number of key points.

The first is that “there are a number of stumbling blocks that prevent children from receiving appropriate dental care” – including distance from/accessibility to a provider, not to mention the costs involved.

Secondly, that the majority of people will be affected by caries: ” [r]oughly 90% of us will have some degree of tooth decay during our lifetime”; that this prevalence increases over time, and that – sadly but unsurprisingly – it is most marked in poorer sectors of society. Interestingly they also characterise caries as infectious – because the bacteria involved can be & are spread from mouth to mouth. (Consequently they advise against ‘spit-cleaning’ a child’s dummy, which sounds just about as insanitary as popping it straight back in from a sojourn on the floor.) And there’s also a genetic component, which means that “[t]ooth decay truly is a complex, multifaceted process that clearly isn’t as simple as forgetting to floss every day or even the socioeconomic status.”

There’s a description of the effect of fluoride on tooth enamel, which says quite explicitly that “when exposed to fluoride either systemically during tooth development or topically via toothpaste, fluoridated water, or professional application, becomes strengthened.” Jones & Ritchey agree that dental and skeletal fluorosis are problems when ingesting higher levels of fluoride, but add a caveat that bears repeating: “It must be emphasized that skeletal and severe fluorosis of the teeth do not occur as a result of any sort of community water fluoridation, or because of fluoride in toothpastes or professional fluoride treatments [my emphasis]. They occur in areas with naturally occurring fluoride levels far in excess of what is safe, and are rare in the United States. In these areas, a defluoridation process must be undertaken to return the water concentration of fluoride to safe and optimal levels.”

And they have some strong words to say on the so-called ‘fluoride controversy’.

As I said, it’s a long-ish piece but well worth reading in its entirety.

For those interested in reading more on this issue, my colleague Ken Perrot has written extensively on fluoridation over at Open Parachute: here, for example.

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