Is water fluoridation better than salt fluoridation?


Discussion of fluoridation here concentrates on community water fluoridation. But some countries (parts of Europe, and Latin America, for example) fluoridate their salt instead of their water.  This could be for a number of reasons – the state of the water reticulation system, or political opposition to water fluoridation, etc.

The effectiveness of community water fluoridation in reducing tooth decay is well established by research, but there has been far less research on the effectiveness of salt fluoridation. Evidence suggests the effectiveness of the two fluoridation methods is similar but new research from Latin  America found water fluoridation significantly better than salt fluoridation.

It’s a very good study, large numbers of subjects and good consideration of possible confounders. But the authors themselves suggest their findings are more relevant to developing countries than developed countries with better oral health systems.

The paper is:

Fabruccini, A., Alves, L. S., Alvarez, L., Alvarez, R., Susin, C., & Maltz, M. (2016). Comparative effectiveness of water and salt community-based fluoridation methods in preventing dental caries among schoolchildren. Community Dentistry and Oral Epidemiology.

The researchers used data from survey of the oral health of 1528 twelve-year-olds in Porto Alegro, South Brazil  (water fluoridated) and 1154 twelve-year-olds in Montevideo, Uruguay (salt fluoridated). Diagnostic procedures were standardised and the data adjusted for gender, maternal education, school type, brushing frequency, use of dentifrice, professional fluoride application, access to dental services and consumption of soft drinks.

Caries prevalence and decayed missing and filled teeth (DMFT) were measured using standard WHO procedures, and modified WHO procedures (which also included noncavitated lesions).

The graphs below show the adjusted data for caries prevalence (%) and DMFT.
Caries water salt

DMFT water salt

Both caries prevalence and DMFT were significantly higher for children from salt-fluoridated Montevideo than similar children from water-fluoridated Porto Alegro.

Apparently this is the first study showing a statistically significant difference between water and salt fluoridated areas. Similar studies in Freiberg, Germany and Dublin, Ireland had shown no signficant differences. The larger sample sizes of the current study may have contributed to the difference. However, the authors also warn that the different situations may also be a factor.

Developing countries have higher prevalence of caries and poorer access to others sources of fluoride than developed countries. Whereas water fluoridation reaches the whole population fluoridated salt may not have such a regular use. In Uruguay the salt fluoridation programme is limited to salt for domestic use. It does not cover public and private canteens, restaurants and bakeries (which the WHO recommends).

So, an interesting study with a clear result – but one that should not be cherry picked to confirm a bias. It indicates community water fluoridation will probably be more effective than salt fluoridation in developing countries – especially if a salt fluoridation programme is not complete. But this should not be used to argue against a good salt fluoridation programme in developed countries.

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22 responses to “Is water fluoridation better than salt fluoridation?

  1. Something to check up on:

    Non-fluoridated Christchurch has fewer Specsavers and optometrists (Yellow pages) per 100,000 people than the other main cities which are fluoridated:
    christchurch 3.67
    auckland 3.78
    wellington 6.53
    dunedin 9.37

    Could fluoridated water and toothpsate be affecting the enolase of the eye-lens? been trying to find myopia prevalence figures.

    I wish FAOSTAT would give Superphosphate manufacture figures across the world. But they give exports. New Zealand and Australia are both big on superphosphate exports and fluoridation. I know USA manufactures a lot and fluoridates a lot. Ukraine is a big exporter but can’t fluoridate since I think fluoride is already too high in water.
    fluoridated tonnes super exports 2008
    Lebanon n 267694
    Australia 80.00% 38034
    Spain 11.00% 31018
    Ukraine n 26895
    India n 19620
    Indonesia n 15872
    Côte d’Ivoire n 13884
    New Zealand 61.00% 11059
    Vietnam 4.00% 6269
    Malaysia 75.50% 4602
    Argentina 19.00% 3943

    Hong Kong 100.00% 0
    Singapore 100.00% 0
    Brunei 95.00% 0
    Irish Republic 73.00% 0
    Chile 70.00% 0
    United States 64.00% 0
    Guyana 62.00% 0


  2. “Could fluoridated water and toothpaste be affecting the enolase of the eye-lens?”

    No-one is stopping you from following the science or even doing your own research, soundhill. I look forward to seeing your research published in a peer reviewed journal.

    To help you, I suggest that you look into the optics of the eye first. You’ll find that the lens has a minor contribution, although important, to the optics of the eye.


  3. Seriously, Brian, there are far more credible hypotheses one could advance to explain the different numbers of Specsavers and optometrists in different cities than your suggestion “Could fluoridated water and toothpsate be affecting the enolase of the eye-lens?”

    You are away with the birds again. 🙂


  4. And for your data for superphosphate – I seriously doubt the figures – perhaps you can provide a source for them.

    I didn’t think the USA produced any single superphosphate any more.


  5. Thanks Ken,
    Here is their above 35% superphosphate if that be the “non-single” stuff., but any NZ figures have not got in.
    My link which you may beed to adjust:
    1000 Iraq
    5500 Iran (Islamic Republic of)
    6000 Algeria
    22465 Japan
    23750 Spain
    47000 Bangladesh
    119020 Turkey
    204000 Lebanon
    215353 Syrian Arab Republic
    687000 Morocco
    808312 Brazil
    862708 Tunisia

    Brazil is a 41% fluoridator and Spain 11%.

    Need to check natural levels in the others which would restrict them putting the fluoride in water.

    May find salt fluoridators are not superphosphate manufacturers. Eg Uruguay it seems.


  6. That was the 2008 recorded figures but this time for production of >35% superphosphate as opposed to exports of superphosphate last time.

    Eye lens can also have an enolase. Yes greater lens curvature shows in myopia.

    If lenses are put in front of chicken eyes their eyes adapt to them.

    Children doing close up work or with lazy lens accommodation could have the same effect.

    What is needed is the ability to readapt.

    Thanks Stuartg it is a bit of a study.


  7. Sorry I meant “eye cornea” can also have an enolase.

    Interesting that contact lenses can stop the cornea growing and reduce the progress of myopia somewhat.


  8. Thanks for the research suggestion Stuartg. I’ve asked Ministry of Education for their vision screening results.


  9. My understanding is that few countries actually produce single super anymore. The USA doesn’t – it produces phosphate compounds (we sometimes call them triple super in NZ) which are used to make fertilisers.

    So the production or trading of superphosphate is really irrelevant. What you want is the data for used of fluoride containing phosphate rocks (and their content varies from source to source) in industrial production.

    Or better still – why not look for production of fluorine compounds from all ores.


  10. soundhill,

    Perhaps you should consider your ideas about enolase and the human lens in a broader context:
    Enolase is found in the cytosol, ie inside cells.
    That’s why enolase is not found in serum; serum is an extracellular fluid.
    The lens of the mature (non foetal) human eye is both avascular and acellular.
    Avascular and acellular means there are no cells in the stroma of the human lens.

    Since there are no cells in the stroma that composes the human lens, your idea would have to explain why an intracellular enzyme is found in an extracellular location and what it’s function would be in that extracellular location.

    It appears that you are constructing a giant edifice but have forgotten about the foundation.


  11. soundhill,

    You are unlikely to find information about the optics of the eye from the Ministry of Education.

    Try a textbook on ophthalmology instead.


  12. soundhill,

    The cornea of the human eye is as acellular and avascular as the lens.

    That’s the reason both are transparent.


  13. “Alpha-enolase expression levels were examined in rabbits during epithelial regeneration after the debridement of corneal edges. The results showed that there was a significant difference in the ratio of ENO1 to total protein levels between uninjured and injured rabbit corneas. However, the role of ENO1 in eye development needs to be further investigated.”


  14. soundhill,

    “the role of ENO1 in eye development (of rabbits) needs to be further investigated.” – and what has this to do with your own statement about enolase in the human eye and children doing close-up work?

    Obviously you didn’t notice that my comment carried on from your own comments about the human eye – I specified the “mature (non-foetal) human eye”

    If you believe that enolase in foetal rabbit eye lenses, with their cellular, vasculitic structure, has anything to do with the mature human lens, which has neither blood vessels nor cells, you have a problem.


  15. Stuartg: “If you believe that enolase in foetal rabbit eye lenses, wittheir cellular, vasculitic structure, has anything to do with the mature human lens, which has neither blood vessels nor cells, you have a problem.”
    Do you think that they were debriding foetal corneas?


  16. soundhill,

    To answer that, maybe you should read your own reference.

    They certainly were not discussing mature human lenses or corneas.


  17. soundhill,

    I am a scientist who is trying to point out where a non-scientist has an “idea”, but has insufficient knowledge to realise that the “idea” does not mesh with the rest of scientific knowledge. You’re getting on your high horse and insisting that you are right, where a scientist would be trying to prove themselves wrong.

    “Could fluoridated water and toothpaste be affecting the enolase of the (human) eye lens?”

    Well, a read of basic textbooks of biochemistry, embryology and ophthalmology would give you the answer “no”:

    Enolase is part of the glycolytic pathway.
    It is found only inside cells.
    It is part of the internal energy source of the cell.
    The energy it produces cannot be exported from the cell.
    The mature human eye has several transparent sections.
    All are transparent because they are acellular and avascular. (Much of ophthalmology is devoted to prevent cells or vascular structures invading those transparent sections).
    During embryogenesis of the eye, the subsequently transparent structures of the eye have blood vessels and cells present.
    During embryogenesis of the eye, the subsequently transparent structures are opaque and have no optical properties because of the cells and blood vessels present in them.
    The optics of the eye become transparent in the mature eye because the cells and blood vessels withdraw as the eye matures.
    Since the stroma of the healthy human cornea and lens are transparent, no cells or vascular structures are present (if they are opaque, because of the presence of cells or vessels, they are unhealthy).
    Since there are no cells or blood vessels within the healthy, mature human eye, there is no place for intracellular enolase to be found.

    Note how biochemistry, embryology and ophthalmology interact in this tiny example. If you’ve only read about the biochemistry, you will have no idea that the science of other topics interacts directly with the biochemistry.

    Now, a scientist would acknowledge what I have just said, thank me, and discard the idea as having minimal chance of being possible (to start with, enolase would have to be shown to have an extracellular function… and be found in the extracellular space).

    Ken said “You are away with the birds again.”

    I prefer to think that you present as someone who hasn’t taken science as a high school class, yet is pretending to have some scientific knowledge. Unfortunately, whilst you may have qualifications as an electronic technician, you are missing several years and/or decades of learning how to think as a scientist.

    Try that high school science class and then maybe learn the basics of a subject from textbooks. Read many textbooks on multiple subjects. Perhaps then you could begin to critically interpret journal articles.


  18. Stuartg: “They certainly were not discussing mature human lenses or corneas.”
    Wrong, they are concerned with human eyes when they say “However, the role of ENO1 in eye development needs to be further investigated.”

    Short-sightedness increases with build up of the cornea, into adulthood.

    Do you expect scientists to be debriding human corneas to study eyes?


  19. Stuartg: “Since there are no cells or blood vessels within the healthy, mature human eye, there is no place for intracellular enolase to be found.”

    And do you think the eye cornea is made of cells?

    From one of the refs of the article I cited: Wistow: “It thus appears that a highly conserved, important glycolytic enzyme has been used as a structural component of lens since the start of vertebrate evolution. Apparently the enzyme has not been recruited for its catalytic activity but for some distinct structural property. tau-Crystallin/alpha-enolase is an example of a multifunctional protein playing two very different roles in evolution but encoded by a single gene.”


  20. soundhill,

    No matter what you say, it doesn’t change the science.

    You obviously have a religious belief in your own fantasies.

    You can check my statements about the development of the human eye by reading a textbook on embryology. Any textbook on embryology.

    You can check my statements about the optics of the human eye by reading a textbook on ophthalmology. Any textbook on ophthalmology.

    You can read about where enolase is found in the human body by reading a textbook of biochemistry. Any textbook of biochemistry.

    Maybe you should add textbooks on anatomy and histology. They will corroborate.

    Extraordinary claims require extraordinary evidence.

    All you have to do to prove your ideas is to overturn the medical textbooks of the world…


  21. The new texts will have to cover proteonomics.


  22. Thank you Ken for your blog specifically on fluoridation issues. My brother alerted me to your blog. I was involved in the swing by the then Country Party of WA from their opposition to fluoridation to the extremely small margin of one to supporting the then Liberal Party of WA. The story of fluoridation in WA is the one I am most familiar with and I am pleased to have subscribed to your blog as I can see that your ability to suss out BS when it is propounded is something I will find pertinent and soothing!!

    Later this year the 50 year anniversary of the passing of the fluoridation bill into the statute books in WA will be celebrated. I am led to understand that Fluoride Free WA will probably mount a protest. . Fortunately it would seem that there is no political appetite to make this an issue.

    V Denyer (nee Lugg)


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