Fluoride: Is Your Water Safe?

The battle over whether we should be putting fluoride in our water has reached fever pitch. We’ve got U. S. Health Secretary Robert F. Kennedy Jr. and anti-fluoride activists saying it’s a neurotoxin that’s lowering our IQs. But supporters say that fluoride is a safe and effective way to protect our teeth from cavities, and that stopping water fluoridation would lead to a spike in tooth decay. To find out who’s right, we talk to epidemiologist Dr. Ashley Malin and community health scientist Professor Lindsay McLaren. Find our transcript here: https://bit.ly/ScienceVsFluoride In this episode, we cover: (00:00) Chapter 1: Why did we start water fluoridation? (07:00) Chapter 2: What can fluoride do at really high levels? (11:18) Chapter 3: Can low doses of fluoride affect the brain? (20:41) Chapter 4: Anything else to worry about? (24:53) Chapter 5: Does fluoride in the water protect our teeth? This episode was produced by Meryl Horn, with help from Wendy Zukerman, Rose Rimler, Michelle Dang, and Ekedi Fausther-Keeys. We’re edited by Blythe Terrell. Mix and sound design by Bobby Lord. Fact checking by Erica Akiko Howard. Music written by Bumi Hidaka, Peter Leonard, Emma Munger, So Wylie, and Bobby Lord. Thanks to all the researchers we spoke to for this episode, including Professor Christine Till, Professor Jonathan Broadbent, Dr. John Morris, Professor Bruce Lanphear, Professor Loc Do, Dr. Maria Kipper, Professor Philippe Hujoel, Professor Stephen Peckham, Dr. Tommaso Filippini, and Professor Steven Levy. Science Vs is a Spotify Studios Original. Listen for free on Spotify or wherever you get your podcasts. Follow us and tap the bell for episode notifications. Learn more about your ad choices. Visit podcastchoices.com/adchoices

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Wendy Zukerman?

  Hi, I'm Wendy Zukerman and you're listening to Science Versus.

• 0:05Wendy Zukerman?

  Today on the show, we are pitting facts against fluoride, should we put it in the water.

• 0:16Wendy Zukerman?

  To tell us all about it, senior producer Merrill Horn. Hello.

• 0:20Speaker 01

  Hi. Okay, there's so much controversy right now around water fluoridation.

• 0:26Wendy Zukerman?

  I know.

• 0:27Speaker 01

  Which we'll get to.

• 0:28Wendy Zukerman?

  Okay.

• 0:29Speaker 01

  But first, I have to tell you the like wild and surprising story about why we started putting fluoride in the water in the first place. Because it is kind of weird that we do this, right?

• 0:41Wendy Zukerman?

  I guess so. How did it all start?

• 0:44Speaker 01

  Well, it's actually a detective story.

• 0:49Speaker 01

  It starts in 1901. So picture a young dentist. Frederick McKay moves to Colorado Springs. And he starts seeing patients and immediately notices that there's something weird going on. A lot of his patients have dark brown stains on their teeth.

• 1:09Wendy Zukerman?

  Mm.

• 1:10Speaker 01

  He writes that the color was sometimes dirty or an almost ebony black.

• 1:17Wendy Zukerman?

  Mm.

• 1:18Speaker 01

  Do you want to see pictures?

• 1:20Wendy Zukerman?

  Of course I do.

• 1:21Speaker 01

  All right.

• 1:22Wendy Zukerman?

  Oh, it's a real black line, thick line across their teeth. That is unsightly.

• 1:32Speaker 01

  Yeah. So McKay starts to obsess over this, searching for an explanation. He writes to a friend at one point who responded, quote, "I have never seen a stain that penetrated the enamel so deeply before." And this guy guessed that maybe the stains came from dead organisms.

• 1:54Wendy Zukerman?

  Mm.

• 1:55Speaker 01

  So like, they had no idea at first, like, what was going on here.

• 1:59Wendy Zukerman?

  I mean, it looks, you could see, it looks like mold on their teeth. I can understand why they went for the dead organisms.

• 2:07Speaker 01

  Yeah. It must have been pretty startling, right?

• 2:11Wendy Zukerman?

  Yes.

• 2:12Speaker 01

  So McKay starts traveling around the US, looking at other places which also have this staining. And he starts suspecting that it's coming from, quote, "something in the drinking water." But he doesn't really know for sure. But then he goes to this town in Arkansas, where people only started getting stains in their teeth if they were born after 1909. And apparently, that's when the town switched water supplies. So now they just have to see what is in the new water supply.

• 2:48Wendy Zukerman?

  Yes, what's different?

• 2:49Speaker 01

  And so someone does this analysis, and McKay finally gets an answer after three decades of searching. It was the fluoride.

• 3:00Wendy Zukerman?

  Right, this new water in Arkansas had higher fluoride levels.

• 3:04Speaker 01

  Yeah, yeah, it had really high fluoride in that water. They weren't adding it, but these places just happened to naturally have a lot of fluoride seeping into the water from the earth's crust. And now we know that when you drink water with high levels of fluoride, it can mess with the crystal structure of your teeth, and that can lead to staining.

• 3:27Wendy Zukerman?

  Right.

• 3:27Speaker 01

  But then McKay also noticed something else that was weird about these people with the stained teeth. They basically weren't getting cavities. So like, even though the fluoride was turning teeth brown, it was also protecting them.

• 3:44Wendy Zukerman?

  That's cool. What a Dr. Jekyll, Mr. Hyde moment.

• 3:49Speaker 01

  Yeah, and so they figured like, okay, what if we could like add fluoride to the water in places that don't already have it? Like, just a little bit so that we can get this like protection from cavities, but not so much that it turns the teeth brown.

• 4:04Wendy Zukerman?

  So this was the beginning?

• 4:05Speaker 01

  Yeah, this is like the birth story of water fluoridation. So in 1945, Grand Rapids, Michigan, was the first city in the US to add fluoride to the water. And people were really excited. The government released a PSA about it.

• 4:19Speaker 02

  The children in Grand Rapids have less tooth decay than they did six years ago.

• 4:25Wendy Zukerman?

  It's working.

• 4:26Speaker 01

  Yeah, they found that it slashed rates of tooth decay by as much as 70%.

• 4:31Wendy Zukerman?

  Wow.

• 4:32Speaker 02

  Now, our children can have better health through fluoridated water. They Drink away tomorrow's tooth decay.

• 4:40Speaker 01

  And after that, we started fluoridating water in most of the US, Australia, Ireland, and a lot of places in Brazil and Canada. And the CDC lists this as one of our greatest public health achievements of the past century, along with vaccines and figuring out that tobacco is bad.

• 4:59Wendy Zukerman?

  Yeah, wow, that's big. That's in the biggies. But then, fast forward to 2025, and people are not excited about drinking away tomorrow's tooth decay.

• 5:15Speaker 01

  Well, there's actually been some opposition to this from the start, but recently, things are really heating up, even at like the highest levels. So, Robert F. Kennedy Jr., who leads the Department of Health and Human Services, he thinks that fluoride is dangerous.

• 5:32Speaker 03

  I think fluoride is a poison.

• 5:35Speaker 01

  But he's not alone. There's a whole kind of chorus of people saying that adding fluoride to the water has been a huge mistake because fluoride is actually really bad for us.

• 5:45Speaker 04

  Fluoride, it's a neurotoxin, and it's found in rat poison.

• 5:48Speaker 05

  It literally drops IQ in children. It helps cause ADHD. It makes our bones brittle and increases hip fractures.

• 5:56Speaker 06

  Fluoride in drinking water absolutely increases the risk of thyroid disease.

• 6:02Speaker 01

  And on top of all the dangers of fluoride, people are also saying now that it doesn't even work to prevent cavities anymore, now that we have better dental care.

• 6:11Speaker 07

  Not only ineffectual, but harmful because of all the science that's emerging.

• 6:15Speaker 02

  Water fluoridation, scientifically proven not to work.

• 6:17Speaker 06

  Is fluoride really the hero that we once thought it was?

• 6:22Speaker 01

  And so now fluoride is being taken out of the water in some places in Australia and now Utah in the US.

• 6:29Wendy Zukerman?

  So, so who's right? Is fluoride the hero that we thought it was? Or is it the nemesis that we people now say it is?

• 6:41Speaker 01

  Yeah, that's the question. And just to say that the research on this was not at all what I was expecting it to be.

• 6:49Wendy Zukerman?

  All right, the science of fluoride is coming up just after the break.

• 7:00Speaker 06

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• 8:30Wendy Zukerman?

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• 9:13Wendy Zukerman?

  Welcome back. Today, we're looking at whether fluoride should be in our water or not. Is it safe or not? Merrill Hahn, PhD, is here with us.

• 9:23Speaker 01

  Hi, Wendy.

• 9:24Wendy Zukerman?

  Merrill, where do we begin? Is fluoride a poison now?

• 9:29Speaker 01

  Well, I mean, like a lot of stuff, at really high levels fluoride can kill you. So the most dramatic example that I found of this was in the 90s, there was a town in Alaska that accidentally dumped like way too much fluoride into the water supply. And like dozens of people got really sick. Someone even died. The case study said that, quote, "After 24 hours of intractable vomiting, a 41-year-old man was found dead at home."

• 10:02Wendy Zukerman?

  Oh, God. How much fluoride did they dump in the water in that case?

• 10:07Speaker 01

  It was way more than we normally put in. So like that water that that guy drank had roughly like 350 times more than what we aim for when we fluoridate water.

• 10:18Wendy Zukerman?

  Wow. Right.

• 10:20Speaker 01

  And at really high levels, it can stop your heart.

• 10:23Wendy Zukerman?

  Okay, right. But there's a lot of things that if you have too much of them can kill you, including water that is not fluoridated.

• 10:32Speaker 01

  Uh huh.

• 10:33Wendy Zukerman?

  The question obviously becomes, are the levels of fluoride that we're putting in the water safe?

• 10:40Speaker 01

  Yeah, that's the thing that everybody's fighting about with, you know, some people saying that it's not safe, some people saying that it is. But there is one downside that kind of everyone agrees is happening, even at these low levels of fluoride that we're putting in the water. And that's the thing that we mentioned at the top of the show, where fluoride can stain your teeth. And that can happen even at lower levels, too. And at that case, it's not like the photos that I showed you of like these brown teeth. It's just kind of like a whitish stain.

• 11:11Wendy Zukerman?

  Uh huh.

• 11:12Speaker 01

  But like 10 years ago, we checked to see how many kids in the US have this, and it was 70%.

• 11:18Wendy Zukerman?

  Mm hmm.

• 11:18Speaker 01

  And so the government took that seriously enough that they changed the recommendation for how much fluoride should go into the water. It was lowered 10 years ago.

• 11:29Wendy Zukerman?

  Okay. What about, the, the big thing I, I hear about now, and I've seen headlines saying this and that and the other, is around fluoride affecting our brains. Some saying it's damaging, others saying it's not. What, what's going on here?

• 11:44Speaker 01

  Yeah, let's dive into that one, since people are really worried about that, and it's also where a lot of the research has been. So to walk us through this, I called up epidemiologist Ashley Malin, an assistant professor at the University of Fluoride.

• 11:59Wendy Zukerman?

  Fluoride. Got it.

• 12:02Speaker 01

  Yep. So Ashley first remembers when she heard about this idea that fluoride might be bad for us. She was with a family member.

• 12:11Speaker 05

  I was drinking a bottled water, and they said, "Don't drink that, there's fluoride in it." And I said, "Yeah, well, it's good for my teeth." And they said, "No, fluoride lowers IQ." And I said, "There's no way that something would be added to the drinking water that could potentially lower IQ."

• 12:28Speaker 01

  And what about it felt kind of implausible?

• 12:30Speaker 05

  Yeah, I was skeptical, because this is a widely-used public health intervention that's supposed to be protecting our teeth, and it's supposed to be something that's good for us. So I just said, "They wouldn't add that to the drinking water if it was harmful in any way." Like, I couldn't even fathom that that was a possibility.

• 12:48Wendy Zukerman?

  Hmm. Yeah, I hear that.

• 12:50Speaker 01

  But, like, she was intrigued enough that Ashley started looking into the research. And at the time, there was a little bit there. Like, there was a study in the 90s that looked at over 500 rats and found that giving them fluoride could change their behavior, like, it made some of them hyperactive.

• 13:10Wendy Zukerman?

  Mm-hmm.

• 13:11Speaker 01

  And then she also found some studies in people, like, in China, there are a lot of places with these really high levels of fluoride in the water.

• 13:20Wendy Zukerman?

  Naturally.

• 13:20Speaker 01

  Yeah, and some of those studies had been finding that people who lived in these areas had lower IQs.

• 13:27Wendy Zukerman?

  So at a high doses, yes, but the question is, what about the low doses?

• 13:31Speaker 01

  Yeah, so that's what Ashley started looking into herself.

• 13:35Speaker 05

  But there were no studies on lower exposures, really, at that time. I was like, huh.

• 13:40Speaker 01

  And so she decided to do her own research on this. She wanted to find out if being exposed to fluoride in the womb could affect brain development. So she got involved in this big study in California. Here's how it worked. So they started following a couple hundred pregnant people. And they're taking pee samples from them. And this way, they could look at how much fluoride was in their pee.

• 14:06Wendy Zukerman?

  Okay.

• 14:07Speaker 01

  And that kind of roughly maps out to how much fluoride you're taking in. But by the way, this isn't just looking at like fluoride from the water because we actually do get fluoride from a bunch of different sources. Something like 60% of it comes from the water. But we also get it from, you know, stuff like black tea. Apparently has a lot of fluoride in it. Pesticides can have it. Or if we swallow little bits of fluoridated toothpaste. So yeah, the researchers here are looking at kind of like overall fluoride exposure.

• 14:37Wendy Zukerman?

  Okay.

• 14:38Speaker 01

  And then they followed up with these moms three years later. So by now their kids are three. And they had them fill out a survey about their kids where they asked them about all sorts of stuff.

• 14:51Wendy Zukerman?

  Mm hmm. It'll ask symptoms of autism, anxiety, depression, attention deficit hyperactivity disorder, physical symptoms, so stomach aches, headaches, temper tantrums.

• 15:04Speaker 01

  Like people will say like, oh, my kid has temper tantrums like all the time. Or like, oh, that's really rare. Like that kind of a thing.

• 15:12Wendy Zukerman?

  Yeah, so it's rated from zero to two. And it'll capture whether the behavior is either typical or kind of over and above what would be considered typical for that developmental stage. Okay.

• 15:26Speaker 01

  So yeah, they're like casting a wide net here to see if people who had more fluoride in their bodies when they were pregnant went on to have kids with more of any kind of like neural behavioral issue when they were three.

• 15:37Wendy Zukerman?

  Uh huh. And so what did they, what did they find?

• 15:40Speaker 01

  So Ashley was working from home, looking at her data on her laptop when she saw the results.

• 15:47Speaker 05

  I'm like, oh, my gosh, someone, I want someone to check this.

• 15:50Speaker 01

  To make sure this is real. Yeah. Because what did you see?

• 15:54Speaker 05

  We found that higher levels of fluoride in pregnant women's urine was associated with more neurobehavioral problems in their children by age three.

• 16:03Wendy Zukerman?

  Mm hmm. What kinds of problems?

• 16:05Speaker 01

  They did have more temper tantrums. They had more anxiety and symptoms linked to autism.

• 16:10Wendy Zukerman?

  Uh huh. And can you put some numbers around this? I mean, when you say more tantrums, more anxiety, I mean, by how much?

• 16:18Speaker 01

  Well, it wasn't like, you know, every kid who had some fluoride in the water got anxiety.

• 16:24Wendy Zukerman?

  Right.

• 16:24Speaker 01

  But what she did is she kind of took the kids who were kind of near the bottom end of getting exposed to fluoride and compared them to the kids who are more towards the higher end of fluoride exposure. And here's what she saw.

• 16:36Speaker 05

  Their children had nearly double the odds of exhibiting the clinically relevant neurobehavioral problems by age three.

• 16:43Speaker 01

  Whoa, doubled odds.

• 16:45Speaker 05

  Nearly double. It was almost double. Yeah.

• 16:48Wendy Zukerman?

  Okay, and it's intriguing. I'm not, it's not a huge study, 200 people.

• 16:59Speaker 01

  Yeah, it's funny. I thought that you would be way more like surprised and alarmed at this study. Like, that's how I felt when I saw this. There was like a turning point for me where I was like, what? Like fluoride might actually be doing something bad here?

• 17:14Wendy Zukerman?

  Yeah. I guess if I'm gonna be honest about my biases here, I sort of where Ashley was before she did the study and she was drinking the water and her family member said, this causes brain damage. And she's like, absolutely not.

• 17:40Wendy Zukerman?

  And because I know the scientific status quo for so long has said, no, it's safe.

• 17:49Wendy Zukerman?

  So I can see myself looking for holes in this paper. It's not a randomized controlled trial.

• 17:57Speaker 01

  Mm hmm.

• 17:57Wendy Zukerman?

  So we can't say that the fluoride caused these differences. There might have been other differences between the groups.

• 18:05Wendy Zukerman?

  So I, but what do other studies show here?

• 18:09Speaker 01

  Okay, so I found eight studies altogether that basically did what Ashley did. So they looked at prenatal fluoride exposure.

• 18:17Wendy Zukerman?

  Right, pregnant women, following pregnant women.

• 18:20Speaker 01

  Mm hmm.

• 18:21Wendy Zukerman?

  Yeah.

• 18:22Speaker 01

  Yep.

• 18:22Wendy Zukerman?

  Yeah, and looking at places with like not huge amounts of fluoride in their water, but kind of relatively low levels, the amount you'd find in a city in Australia or the US that fluoridates their water.

• 18:33Speaker 01

  Yeah, yeah, and then they followed their kids and looked for behavioral issues or sometimes lower IQ. So, okay, so out of those eight studies.

• 18:44Wendy Zukerman?

  Right.

• 18:44Speaker 01

  Six of them found bad stuff. And two of them didn't find anything bad. So six out of eight studies did find some sort of like negative effect on the brain from prenatal exposure to fluoride.

• 18:57Wendy Zukerman?

  Yeah, huh.

• 18:59Speaker 01

  But the thing is, that's all just one group of studies. So other scientists tackle this in a completely different way. And they'll zoom in on water fluoridation specifically and ask, if you grew up with fluoridated water, do you have a lower IQ later in life?

• 19:17Wendy Zukerman?

  Mm hmm, right.

• 19:18Speaker 01

  And a lot of those studies don't find any differences.

• 19:22Wendy Zukerman?

  Oh, that's so confusing. Suggesting what? That in Ashley's studies, in those prenatal studies, it's not from drinking the water that's the problem, but from swallowing toothpaste?

• 19:35Speaker 01

  I mean, it could be these other sources, yeah. It could be like that maybe it's not the fluoride in the water. It could be they're all drinking a lot of black tea or something.

• 19:46Wendy Zukerman?

  Right.

• 19:46Speaker 01

  It could also be the difference in when the kids are getting exposed, because a lot of the studies finding effects, they're looking at kids who are exposed in utero in their fetuses, and a lot of the ones that aren't are looking after they were born. Another thing that we haven't talked about yet here is that we don't really know what the mechanism would be yet. Like, there are some ideas, but researchers aren't really like coalescing around one thing that is happening.

• 20:11Wendy Zukerman?

  Okay, interesting. I mean, it's because it's such a huge call to say. So basically, that in all of the places that have added fluoride to the water in the US, Australia, Canada, Ireland, is there any evidence that on a population-wide level, that those populations are dumber than places that have not fluoridated the water?

• 20:33Speaker 01

  No. And in general, IQs have been going up, like in places like the US.

• 20:39Wendy Zukerman?

  Hard to see that now, but.

• 20:41Speaker 01

  And like even one researcher who thinks that there is something here estimated that the difference between like growing up in a community with fluoridated water and not is only the difference of like two and a half IQ points. So that feels like not that big a deal.

• 20:58Wendy Zukerman?

  Mm hmm. And so where are you at with this now?

• 21:02Speaker 01

  Well, I live in New York City and we do have fluoridated water here.

• 21:06Wendy Zukerman?

  Right.

• 21:06Speaker 01

  But like I haven't stopped drinking it. Like I'm not worried about it for my brain or or my kids' brains. Like, I just don't think the evidence is there yet. But I do think that if I were pregnant, like if I had known all this when I was pregnant, then I would have avoided drinking fluoridated water then.

• 21:26Wendy Zukerman?

  Really?

• 21:27Speaker 01

  I don't know. I've talked to enough researchers on this pregnancy thing specifically that say, you know, they would not do it. They would not drink fluoridated water. That it freaks me out now, yeah.

• 21:38Wendy Zukerman?

  So then what are you supposed to do if you're pregnant? Get a new water supply?

• 21:42Speaker 01

  I mean, it's really hard, right? Because in theory, like you could try bottled water, but we don't actually know a lot of the time how much fluoride is in bottled water. Some of it might have fluoride in it, too.

• 21:54Wendy Zukerman?

  Yeah, and then you got to worry about the bloody microplastics with the hormone disruptors that we talked about last season.

• 22:00Speaker 01

  I know. Like, I think it's not perfect, but like I would would probably look into a filter. There are some filters that get fluoride out of the water. Or honestly, if it was just for a limited period of time, like if I were pregnant, maybe I would just buy distilled water that didn't have any fluoride in it and like try to drink that. But like this is all probably being super cautious since tons of kids are exposed to fluoride in the uterus and don't have these behavioral issues. And there are just still some big unknowns.

• 22:31Wendy Zukerman?

  Okay, so where we're at with the brain stuff and fluoride is that there is some emerging evidence that if you're pregnant, this could be doing something to the fetus. The science is still unclear, but based on where it's at, you think it's worth thinking about.

• 22:50Speaker 01

  Yeah.

• 22:51Wendy Zukerman?

  For us big kids, come out of the vagina, making podcasts, is there other stuff that we need to worry about?

• 23:00Speaker 01

  Well, it's not just about the brain here. Like, some people are worrying that fluoride might be making our bones weaker or increasing our risk of thyroid disease, like hypothyroidism.

• 23:12Wendy Zukerman?

  Yeah.

• 23:12Speaker 01

  And there is some evidence that that stuff is real, too, even at relatively low levels.

• 23:18Wendy Zukerman?

  Really?

• 23:18Speaker 01

  Yeah, yeah, so like for for the thyroid, like, we know that the thyroid needs iodine, right? If you don't get enough iodine, then you can get a goiter.

• 23:29Wendy Zukerman?

  Yes.

• 23:29Speaker 01

  So fluoride can sort of outcompete iodine. So in the past, we've actually given fluoride as a treatment for people who have overactive thyroids. And there was a study that found that people who lived in an area with fluoridated water were twice as likely to have hypothyroidism than people who didn't. But like other studies haven't found those associations. Or like Juan found that it was only significant if you also had an iodine deficiency to begin with.

• 23:59Wendy Zukerman?

  So what do we make of that as well? What do you make of it?

• 24:02Speaker 01

  Yeah, I mean, it's not like I looked at the evidence and was like, oh, this is real for sure. Like fluoride is giving us all hypothyroidism. And then for other stuff, it's even less convincing. Like for bone health, there were some studies that say that drinking fluoridated water can increase your risk for bone fractures. But there was a meta-analysis that looked at everything together and said that there was no increased risk.

• 24:26Wendy Zukerman?

  Uh huh, reassuring.

• 24:31Speaker 01

  But then, like, I don't know, for me, even if there are just a few studies saying that some of these risks could be real, it doesn't make me feel great because like, I mean, the stakes are so high. We're doing this at such a big scale that ideally you'd want to see like a mountain of rock solid evidence of studies all saying this is totally safe. Like, this is OK to be basically forcing this many people to be having this chemical.

• 24:57Wendy Zukerman?

  Right.

• 24:57Speaker 01

  And we don't have that. I talked to Ashley about why we don't have a more definitive consensus on this. I mean, why, why has it taken so long? Is this kind of a failure of, of science? I think a big part of it is that it wasn't acceptable to ask these questions up until recently. To even ask the question, you'd be considered a tinfoil hat wearing conspiracy theorist, probably up until 10 years ago. Wow. Yeah. That recent? Yeah.

• 25:27Wendy Zukerman?

  All right. Well, this, this episode has taken quite the turn.

• 25:31Speaker 01

  Yeah.

• 25:32Wendy Zukerman?

  I mean, clearly fluoride is not the devil or, or poison as some people are claiming at the, you know, levels we put in our water. But it, it really is frustrating that we don't have more science on this and, and the science that we have is muddy. I guess that's why you see these big fights online with people, some saying it's safe, some saying it's not, because you really can cherry pick the data on all these fronts. You can pick your, it's bad for the thyroid study and you can pick it's bad for the brain study or, or you can pick a study that's saying the opposite. I guess this, but what it does tell us though, the fact that for, for a lot of this stuff,

• 26:17Wendy Zukerman?

  it is muddy and that you do see studies showing both sides, tells us that whatever fluoride is doing in the water, it's not super dramatic. Because then you would see the same results in, you know, basically all studies.

• 26:32Speaker 01

  Yeah, that seems true.

• 26:34Wendy Zukerman?

  OK, so we've talked a lot about the potential risks. Now we need to talk about the potential benefits. The reason that we have been doing this in the first place is to protect our teeth. So is fluoride still doing that?

• 26:51Speaker 01

  That's after the break.

• 27:01Speaker 03

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• 27:43Speaker 03

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• 28:05Wendy Zukerman?

  Welcome back. Today, we're talking about fluoride. Merrill, any benefits to putting it in the water?

• 28:11Speaker 01

  Well, scientists all agree that back in the 1940s, when we first started doing this, there was this huge benefit. But lots of people today are saying that things are different now. And I think it does kind of make sense because when we first started doing this, our teeth were way worse. Like, we didn't go to the dentist as often. We didn't get sealants or brush our teeth with fluoridated toothpaste.

• 28:35Wendy Zukerman?

  Right.

• 28:36Speaker 01

  So something like putting fluoride in the water had this big potential to make a huge difference because our teeth were so crappy.

• 28:43Wendy Zukerman?

  Right.

• 28:44Speaker 01

  Where now people say that, like, well, we don't really need to be doing that anymore because we have all these other, like, you know, tools in the toolbox to help our teeth.

• 28:52Wendy Zukerman?

  So are they right? I mean, does adding fluoride to the water, is it still preventing cavities or not?

• 28:59Speaker 01

  Well, now we actually have like kind of a perfect opportunity to look at this because as cities are taking fluoride out of the water

• 29:07Speaker 06

  Right.

• 29:07Speaker 01

  Today, we can see like, okay, how much like do the teeth actually get worse in places that do that?

• 29:13Speaker 06

  Right.

• 29:14Speaker 01

  And so that's what I wanted to talk about with Lindsay McLaren. She's a professor in community health sciences at the University of Calgary in Canada. And this all first got on her radar back in 2011 when her city decided to stop putting fluoride in the water.

• 29:30Speaker 06

  When it, when that all came out, I just, it was just fascinating to me. Like, oh, we're not going to have fluoride in the water anymore. Isn't, isn't that interesting?

• 29:39Speaker 01

  And Lindsay and some of her public health like nerd friends saw this and they published an op ed in the local paper, just kind of questioning whether this was actually a good idea.

• 29:49Speaker 06

  And like the hate mail came instantly, like we got hate mail immediately.

• 29:56Speaker 01

  Saying what?

• 29:57Speaker 06

  Yeah. Oh, just like, you know, you guys are liars and you know, you're, you're fraudulent. And I was like, oh, okay. This is very interesting.

• 30:07Speaker 01

  You're like, let's dive deeper into this field where I'm getting hate mail.

• 30:09Speaker 06

  Well, exactly, exactly. Because I actually, and I feel like this is something where I was kind of misunderstood. Like I was actually genuinely open to some of the comments I was receiving.

• 30:22Speaker 01

  So Lindsay was like, yeah, let's do some science here. Like we're, we're taking fluoride out of the water. Will our teeth get crappier?

• 30:29Speaker 06

  Yeah.

• 30:30Speaker 01

  And I wanted to talk to her about this one study that she did looking at cavities in kids. They did this one about seven years after the city stopped water fluoridation. And so they, they looked at kids who had basically gone their entire lives without fluoride in the water. So these kids were about seven years old. And they, they started by sending out teams of dental hygienists and researchers to schools in Calgary to check their teeth.

• 31:00Speaker 06

  So they were just all over the city, you know, for an entire year.

• 31:05Speaker 01

  They would like set up shop in the nurse's office usually where dental hygienists would look at each kid's mouth one by one for signs of tooth decay. And Lindsay's team wanted to make sure that the kids felt comfortable with this.

• 31:19Speaker 06

  In fact, the kids seemed to find it kind of fun. And like we'd have sort of groups of five kids come in at a time and be on deck. And like they'd be dancing around and like they thought it was fun because they got pulled out of class and because of the dental light, we had sunglasses for them and they loved the sunglasses. Like they were just walking around like they were so cool.

• 31:41Speaker 01

  It's like a dance party.

• 31:42Speaker 06

  Yeah, yeah, it was, it was really cute.

• 31:45Speaker 01

  And they weren't just looking at these kids in Calgary that had lost fluoride from their water. They were also doing this entire thing in another city that was nearby called Edmonton that kept fluoridating their water.

• 31:59Wendy Zukerman?

  Listen, what did they find? You're stringing me along like Floss here.

• 32:05Speaker 01

  Okay, okay. So yeah, we've got 5,000 second graders across these two cities and now they can finally see, did the kids who grow up with fluoride added to the water have fewer cavities compared to the kids in Calgary?

• 32:19Wendy Zukerman?

  Yes. So what did they say?

• 32:21Speaker 06

  So the prevalence of dental caries in Calgary kids in their baby teeth was about 65%.

• 32:29Wendy Zukerman?

  Fluoride no longer in the water. 65% had cavities.

• 32:35Speaker 01

  Mm-hmm.

• 32:35Wendy Zukerman?

  All right, drum roll. What is it when fluoride is in the water?

• 32:41Speaker 06

  That was compared to about 55% in Edmonton.

• 32:45Speaker 01

  It's like 10 percentage points different.

• 32:47Speaker 06

  Yeah, yeah. So that's the percent of kids that have any, any cavities at all.

• 32:52Speaker 01

  Like, what did you think when you saw that data?

• 32:54Speaker 06

  This was larger than I expected.

• 32:58Wendy Zukerman?

  Okay. And what, and what about other studies?

• 32:59Speaker 01

  So other studies generally find the same thing. Kids do tend to get more cavities when they grow up without fluoridated water.

• 33:07Wendy Zukerman?

  Okay. Okay. So one thing that we've been told about fluoride, still true, still good for our teeth.

• 33:14Speaker 01

  Yeah, these kids are getting fewer cavities. And I know maybe you're thinking, who cares? Little cavity here or there, maybe it doesn't matter so much.

• 33:24Wendy Zukerman?

  Right. It's just their baby teeth. They're gonna get more.

• 33:27Speaker 01

  Well, it actually does matter. So like if you lose your baby teeth early, like if you have to get them extracted, then your adult teeth might not come in as straight. So that could affect you for the rest of your life. And we do have evidence that living in a place with less fluoride in the water will make it more likely that kids will need to get teeth extracted and also get intense dental work done, like where they'll need to go under general anesthesia, which ideally, like, we'd want to avoid putting kids through that.

• 33:59Wendy Zukerman?

  Yeah.

• 34:00Speaker 01

  And we also have evidence that fluoride is particularly good for kids who come from poorer families. Like, in Lindsay's study, after Calgary stopped fluoridating their water, it widened the gap between the richer and the poorer kids when it came to like how bad their teeth were. Not all studies find this to be true, but Lindsay's does seem to be like one of the best ones.

• 34:22Wendy Zukerman?

  And so what about adults? Does it matter for the, for us?

• 34:28Speaker 01

  Well, it's like, it's kind of hard to tell how much it matters. Like, if you're already an adult and you live in a place with fluoridated water, how much that makes a difference? Like, one study said that there was just 2% less tooth decay for adults who lives in places with more fluoride in the water.

• 34:45Wendy Zukerman?

  Oh, it's tiny. Is that because we're better at brushing our teeth than kids?

• 34:50Speaker 01

  Partly, yeah, actually. And also, apparently, I just learned this, that the enamel of baby teeth is thinner and more porous. And then even after you start getting your adult teeth, those teeth are also more cavity prone since they're softer. It takes them years for them to reach maximal hardness, according to one paper.

• 35:13Wendy Zukerman?

  Wow. Maximal hardness?

• 35:16Speaker 01

  Yeah.

• 35:17Wendy Zukerman?

  That's an odd way to just describe anything to do with children.

• 35:23Speaker 01

  So, yeah, it's like pretty convincing to me that fluoride in the water is still helping our teeth.

• 35:28Wendy Zukerman?

  Right.

• 35:29Speaker 01

  Which brings us back to Lindsay's study. So there's one more thing I wanted to tell you about that, which is about how people reacted to it in Calgary. So

• 35:38Wendy Zukerman?

  Uh huh.

• 35:39Speaker 01

  After her studies came out, the town actually ended up voting on this and decided to put fluoride back in the water.

• 35:47Wendy Zukerman?

  Whoa.

• 35:49Wendy Zukerman?

  They listen to the teeth science. They care about their teeth.

• 35:54Speaker 01

  Yeah, it seems like it. Like, they had a vote, and 62% of the people said, "Yes, we want to fluoridate our water again."

• 36:02Speaker 06

  And this was by far the largest majority in our history. It was, in the past, it's been more like, you know, 49, 51 type of thing.

• 36:12Speaker 01

  Oh, wow.

• 36:13Speaker 06

  Yeah, so this was quite a strong sign of support.

• 36:16Speaker 01

  Yeah, so her study got a lot of attention, like, even in the US. Here's some of that coverage.

• 36:22Speaker 03

  In Calgary, there was life before fluoride was removed from drinking water and life after. Children, mostly children, had to suffer so badly.

• 36:33Speaker 01

  So, yeah, I asked Lindsay, like, where she lands after all this. Should we be putting fluoride in the water?

• 36:40Speaker 06

  Yes, at recommended optimal concentrations. And keep the research going. So, so don't cut research funding. That seems like a pertinent thing to say right now.

• 36:50Wendy Zukerman?

  Sure does, sure does. All right, well, but Lindsay's looking at the teeth. Was she also thinking about all of the other potential risks around brain development and thyroid stuff when she answered that question?

• 37:03Speaker 01

  Yeah, we talked about that research. Like, it's something she's keeping an eye on, but so far, it hasn't changed her mind on water fluoridation in general.

• 37:12Wendy Zukerman?

  Hmm.

• 37:15Wendy Zukerman?

  Ooh, messy. I mean, zooming out here, you did speak to a lot of scientists in this space. What are they telling you when, when they put the risks and the benefits together here? Where do they stand?

• 37:29Speaker 01

  I mean, they were really split, actually. I was surprised by how many scientists, including some dentists, who told me they think we should either stop or they were, like, seriously doubting it. Like, there is one that I talked to who used to be a big fluoride supporter. And he'd been thinking more and more about this research. And I asked him, like, all right, like, if you're in charge of the machine, do you cut it off?

• 37:55Wendy Zukerman?

  Yeah.

• 37:55Speaker 01

  And he just, like, paused for 20 seconds in silence while he, like, tried to figure out what to say. And then he just said, like, sorry, I can't give you an answer. We need more research.

• 38:06Wendy Zukerman?

  Wow.

• 38:07Speaker 01

  Which is kind of where I'm at. Like, I just, I keep turning this over in my brain.

• 38:11Wendy Zukerman?

  I was just, so Meryl, do you think we should keep fluoridating the water?

• 38:15Speaker 01

  I don't know. I am right there with him because, like, I can really see it from both sides. I think what's so hard about it for me is that I'm pretty convinced that the benefit to the teeth is real. But it's like, at the end of the day, it's still just the teeth. Where like, even if the science on the brain damage isn't as convincing, the stakes are so much higher that if the effect is real, we need to stop fluoridation, even if it is good for the teeth. Obviously, we can't be giving people something that might be damaging their brains.

• 38:48Wendy Zukerman?

  Right, right.

• 38:50Speaker 01

  What do you think?

• 38:56Wendy Zukerman?

  That's science versus.

• 38:57Speaker 01

  Hey.

• 39:01Wendy Zukerman?

  20 seconds of silence, is that about it?

• 39:07Wendy Zukerman?

  Okay, so, Meryl, how many citations are in this episode?

• 39:11Speaker 01

  We had a lot, 105 citations.

• 39:15Wendy Zukerman?

  Whoa, 105, wow. So before you send us angry emails, Instagram messages, please have a look at our transcript. How could people find these 105 citations?

• 39:30Speaker 01

  Yeah, you can go to the show notes and then follow the links to the transcripts. But you can also send the angry emails if you want, you know? We don't mind.

• 39:39Wendy Zukerman?

  It's true. If you, on Instagram, we are science underscore V S. My TikTok is at Wendy Zukerman. Come say hello. Let us know what you thought of the episode. All right, thanks, Meryl.

• 39:52Speaker 01

  Thanks, Wendy.

• 40:00Wendy Zukerman?

  This episode was produced by Merrill Horn with help from me, Wendy Zukerman, Rose Rimla, Michelle Dang, and Akedi Foster Keys. We're edited by Blythe Terrell. Mix and sound design by Bobby Lord. Fact checking by Erica Akiko Howard. Music written by Bumi Hidaka, Peter Leonard, Emma Munga, So Wiley, and Bobby Lord. Thanks to all of the researchers that we spoke to for this episode, including Professor Christine Till, Professor Jonathan Broadbent, Dr. John Morris, Professor Bruce Lanthea, Professor Lochto, Dr. Maria Kipper, Professor Philippe Haudjou, Professor Stephen Peckham, Dr. Tommaso Filippini, and Professor Stephen Levy. Besides Versus is a Spotify Studios original. Listen to us for free on Spotify or wherever you get your podcasts.

• 40:43Wendy Zukerman?

  And if you are listening on Spotify, follow us and tap the bell icon so that you get notifications when new episodes come out. I'm Wendy Zukerman. Back to you next time.

• 40:59Speaker 06

  I used to wonder what I missed any time I stepped out of the shop. But with AT&T Business Wireless, my signal stays strong no matter where the day takes me. Like right now, I'm meeting a photography client

• 41:12Speaker 06

  out here. But I still have a reliable connection, even though I have no idea where I am right now.

• 41:19Speaker 02

  Keep your business connected with AT&T Business Wireless. Visit att.com/5gnetwork. When the connection matters, it has to be AT&T.