Fluoridation Lowers IQ – Significantly?

Fluoridation Lowers IQ - Significantly?The argument about whether to fluoridate municipal drinking water is far from over. This is not for lack of study. At clinicaltrials.gov the results of 193 separate studies are given. Of those, 74 were sponsored by industry — mostly toothpaste manufacturers. The other studies were performed under government sponsorship, grants from research institutions, etc. In spite of this long history of research, the latest publications often stir things up by playing into or against prejudices based on previous thought. Consider a recent study performed at Harvard, which indicates that drinking fluoridated water lowers IQ significantly.

That catches your attention, doesn’t it? “Lowers IQ significantly” is a shocker, and the article has instant credibility because it comes from Harvard. But if you interpret that headline to mean that fluoridation turns people into raving idiots, then you have probably not read the article. The average decrease in IQ found in the study was a 0.5 point reduction. The “significant” reduction means that, when the statistical analysis was performed allowing for such things and the natural variation in IQ, the detected half a point reduction among fluoride users is statistically significant. That is, the lower IQ is not an artifact or sampling error within some degree of probability. Determining if that level of reduction significantly reduces the effective intelligence of the population is beyond the purview of the article, but many people skimming through it will interpret the results to mean that fluoridation induces feeble-mindedness. In fact, IQs vary as much as 20 points when a child becomes a teenager according to an NPR article, which is 40 times more significant in some sense. (The IQs shift plus or minus, not always down, as some parents suspect!)

Nonetheless, Fluorides are known poisons. That is not in dispute. So let us talk about poisons. Water in sufficient quantities causes severe pain and/or death. Excess oxygen will kill you. Both are necessary for life. The dosage is important. Poisonous side effects of beneficial intakes are inevitable with everything.

Truly significant IQ reduction is noted in many studies of the effect of cocaine and alcohol on infants. Stress reduces IQ (which might help explain the teenager variations). Sugar is implicated in more disorders than I can shake a stick at. Since all things are poisons in large quantities, we need to consider the optimum dosage of everything we ingest. In this way, we hope to maximize the benefit while minimizing the detriment. Even cocaine has beneficial uses. It is used for several types of medical procedures where the potential harm is inconsequential compared the good: similarly with the other substances.

The case for deciding the optimum dosage for fluoride additives is complicated by the difference between the benefits and costs. Is eliminating tooth decay worth suffering a 0.5 average decrease in IQ? Many people would say absolutely not while continuing to feed their children sugar, exposing them to alcohol and second (or first) hand smoke and maybe being sloppy with seatbelts. What does it mean to have a population decrease 0.5 point? Can that be overcome by lowering the average stress of filling cavities? I don’t know. A good analogy is that we have a fixed amount of money and want to spend it on healthy food. Should we buy all apples or all oranges? Is a mixture better? Maybe we should consider mental health as part of the problem and set aside a fraction of the food money for comfort food or alcohol, which makes us feel better even if it is not making our bodies better. The problem is difficult because, in real life, we must always make comparisons between apples and oranges. Is the tradeoff of lowering or eliminating cavities worth the exposure to nasty side effects? Maybe it is. Suppose you conclude that the benefits outweigh the costs. Then what?

You study all the research and conclude that there is a non-zero optimum dosage for your family; should you be forced to accept it? That is, should government be permitted to fluoridate municipal drinking water? Governmental intervention is different from deciding to use fluoridated toothpaste or not. Compare fluoridating water with inoculation against diseases. We accept mandatory inoculation to protect against childhood diseases, even though in a very small percentage of the inoculations, something goes wrong (not autism — that is bogus ). The difference between inoculation and fluoridation is that by inoculating children, we prevent the spread of disease to innocent bystanders. By mandating preventative measures, we protect more people than just those being inoculated. In contrast, preventing cavities is a more personal benefit even if the results are equally important. Cavities are not contagious like measles.

I have looked at many of the articles cited above and read pro and con advocacy pieces galore. For me, the bottom line is that voluntary use of fluoridation is, over all, a good thing for a person’s health, but forcing it on everybody is a bad thing — especially since alternatives to mass delivery via municipal water exist. The first part of the previous sentence is based on scientific reasoning; the second part after the word “but” is a political statement. You are welcome to challenge either half, but be clear in your own mind if you are responding scientifically or politically.

It has been pointed out many times that more money is spent fighting for and against gun control than is spent on studying whether or not gun control is a good thing. I feel fluoridation is in a similar state. So if you respond to this piece, either pro or con, please cite the source of your information and, if possible, who sponsored the work. There are enough unsupported accusations flying around. I do not want to become a vector for spreading more of them.

CC licensed Flickr photo by cogdogblog

Article Written by


  1. I’ve gone with “natural” toothpaste over the past few years… can’t say I feel any smarter. :)

  2. sdeforest says:

    Maybe you are still drinking the water.

  3. I wavered whilst reading that. Sometimes you seems more sensible than other times but overall I think you are basically right. Except that I do not accept that alcohol and comfort food are not beneficial. That is to say that naturally in high quantities they can be damaging just as anything beneficial can but there are reasons why we like them and that is that in low quantities they are what we need. When the body has been educated by a good diet the body will force views upon your mind about what is appropriate as a comfort food. For me it is oats and berries. Likewise the body will tell you at what point alcohol ceases to be beneficial, you just have to listen. It has been shown that alcohol can raise IQ by the same amount that fluoride apparently lowers IQ but only in the correct quantities.

    And of course there is the fact of which I am sure you are aware, but for the benefit of any other readers, that as the mind and the body are inextricably connected, what is of comfort to the mind may also be of benefit to the body.

  4. sdeforest says:

    I tried to say that comfort food and alcohol could be beneficial for the mind at the same time they might be harmful to the body. Of course, mind and body are not truly separate items as you say in the last sentence. Overall, we seem to be in agreement. The biggest issue for me is how we decide on free choice vs. governmental interference.

  5. Jonathan says:

    Fluoride is unavoidable. When it’s in the water supply, it’s also your soda and your juice if those are made in fluoridated areas. It’s in the water that feeds your vegetables. It’s in the meat you eat because the animals drink it. It’s in bottled water.

    When the study says “unfluoridated area” they’re only talking about the drinking water in the area. But those people are still having fluoride added their diet.

    So it may be that even “unfluoridated areas” have a 0.5% lower IQ because of fluoride from other outside sources, and the fluoridated areas have an additional 0.5% lower IQ. 

  6. sdeforest says:

    Could be. It is a numbers game. One problem is that the numbers get smothered by advocates of either side of the issue.

  7. Asoka says:

    It seems that America is being dumbed down by something. But I feel that its more the politics and political advertising than fluoride.

  8. chezjuan says:

    The flip-side to the question of adding fluoride: Should the government remove fluoride from municipal sources where it naturally occurs in the water supply?

  9. bern says:

    Absolutely right on the money. I wish I had written it.

    In my youth I was involved in doing research, and we often had to make a distinction between “statistically significant” and “clinically significant”. The results of this study are clearly statistically significant, and clinically insignificant.

  10. Flouride Boy says:

    Is it a half point or a half percent? There is a difference for some of us. A half point is less than a half percent for me, and a half percent would be over a half point. Since we’re talking minuscule but statistically significant numbers here, I have to point out that the difference between the two for me is huge. I mean since I grew up in a flouridated area, my IQ might be lower by almost a whole point!

  11. HarryMonmouth says:

    Agreed. There should certainly be an opportunity to opt out if we choose. Although I had forgotten about reading this item I had considered buying bottled water as an alternative a couple of times over the last day so I guess you must have made me think. There are many areas in which I dispute the government line but at the same time there are so many people who do not think at all and would possibly opt out of things which would be of massive benefit to them. However, I reckon those people would probably need that extra half an IQ point more than your average man in the street.

  12. sdeforest says:

    Presumed clinically insignificant. I think so too, but without massaging the raw data, we do not know. Thanks for the great comment.

    BTW, in psychology they use JND (Just Noticeable Difference). Less well known is the JVD (Just Valuable Difference)

  13. sdeforest says:

    Good point. That also addresses what is natural? Is natural good? Advertising wants us to think so, but by natural processes, I would have been dead long ago.

  14. sdeforest says:

    Good point. How many IQ points does it cost you to listen to a full season of political ads?

  15. sdeforest says:

    I am surprised that you can write as well as you do given that handicap. Did you have help?

  16. sdeforest says:

    “average man in the street” –> “average person on the street”

    Glad my piece made you think. That is what it is all about.

  17. Dusty Dave says:

    This reminds me how long this debate has been going on. In 1958-59 I was a sophomore in high school. I remember that our town was considering fluoridating the water and many people were sure it was a Communist plot (it was 58-59). Our biology teacher ranted that anyone who was against it was an idiot. I don’t remember much biology, but I remember that.

  18. sdeforest says:

    What do the communists gain by making us stupid? We do that pretty well on our own. Look at the international test scores