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Charles C. Mann 10 Sep 18
Hey, a couple days ago I mentioned people who hate water fluoridation in a tweet. I got angry email about the awfulness of fluoridation. I hadn’t realized how vigorous the argument about fluoridation still is, at least for some people. 1/6
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Charles C. Mann 10 Sep 18
Replying to @CharlesCMann
So I wondered what the evidence was for fluoridation's impact. I found a Cochrane Collaboration review of the evidence from 2015: 2/6 (The Cochrane people are kind of the gold standard for systematic reviews.)
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Charles C. Mann
So... Most fluoridation studies were done pre-1975, when fluoridation was coming in. According to Cochrane, *97%* of them were awful, cuz most epidemiological studies were bad back then. There were 0 usable studies, for ex., “on the benefits of fluoridated water for adults.” 3/6
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Charles C. Mann 10 Sep 18
Replying to @CharlesCMann
More: the old studies occurred just as fluoride toothpaste came into use. If I read the report right, researchers then didn’t account for its effects, so you don’t know how much of today’s better dental health is due to fluoridated water, and how much to fluoride toothpaste. 4/6
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Charles C. Mann 10 Sep 18
Replying to @CharlesCMann
My emailers were right! The quality of the pro-fluoridation data is surprisingly weak. Overall, the Cochrane folks saw a positive impact from fluoridated water, but they had “limited” confidence in the size of the “effect estimate.” They wanted “more contemporary studies.” 5/6
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Charles C. Mann 10 Sep 18
Replying to @CharlesCMann
But I bet those studies will never occur. To do them, you’d need a pot of money, years of time—and large numbers of people switching from fluoridated systems to non-fluoridated, and vice versa. 6/6
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Charles C. Mann 10 Sep 18
Replying to @CharlesCMann
Because both sides are certain, there's no demand for these studies. So the argument will continue, forever. People’s teeth will continue to be better, but nobody will **really** know why. /fin
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