Science Vs - Fluoride: Is Your Water Safe?

Episode Date: April 10, 2025

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

Hi, I'm Wendy Zuckerman and you're listening to Science Versus. Today on the show we are pitting facts against fluoride, should we put it in the water. To tell us all about it, senior producer Meryl Horne, hello. Hi. Okay, there's so much controversy right now around water fluoridation. I know. Which we'll get to. Okay.

But first, I have to tell you the 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? I guess so. How did it all start? Well, it's actually a detective story. It's kind of weird that we do this, right? I guess so. How did it all start? Well, it's actually a detective story. 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. He writes that the color was sometimes dirty or an almost ebony black. Do you want to see pictures? Of course I do. All right. Oh, it's a real black line, thick line across their teeth.

That is unsightly. 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. So they had no idea at first what was going on here. I mean, you could see it looks like mold on their teeth.

I can understand why they went for the dead organisms. Yeah. It must have been pretty startling, right? Yes. 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. Uh-huh. 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. Yes, what's different? And so someone does this analysis, and McKay finally gets an answer after three decades of searching. It was the fluoride. Right, this new water in Arkansas

had higher fluoride levels. 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. 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. 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 like protecting them. That's cool. What a Dr. Jekyll, it was also protecting them. That's cool. What a Dr. Jekyll, Mr. Hyde moment. Yeah, and so they figured, okay, what if we could add fluoride to the water in places

that don't already have it, just a little bit so that we can get this protection from cavities but not so much that it turns the teeth brown. So this was the beginning? 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. The children in Grand Rapids have less tooth decay than they did six years ago.

It's working. Yeah, they found that it slashed rates of tooth decay by as much as 70%. Wow! Now, our children can have better health through fluoridated water. They can drink away tomorrow's tooth decay. 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. 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. Well, there's actually been some opposition to this from the start, but recently things are really heating up even at the highest levels. So, Robert F. Kennedy Jr., who leads the Department of Health and Human Services, he thinks that fluoride is dangerous.

I think fluoride is a poison. But he's not alone. There's a whole chorus of people saying that adding fluoride to the water has been a huge mistake, because fluoride is actually really bad for us. Fluoride, it's a neurotoxin and it's found in rat poison. It literally drops IQ in children, it helps cause ADHD, it makes our bones brittle and increases hip fractures. Fluoride in drinking water absolutely increases the risk of thyroid disease.

And on top of all the like dangers of fluoride, people are also saying now that it doesn't even work to prevent cavities anymore, now that we have like better dental care. Not only ineffectual, but harmful. Because of all the science that's emerging. Water fluoridation, scientifically proven not to work. Is fluoride really the hero that we once thought it was? Was, was, was, was, was, was, was, was, was, was, was, was.

And so now fluoride is being taken out of the water in some places in Australia and now Utah and the US. 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? Yeah, that's the question. And just to say that like the research on this was like not at all what I was expecting it to be.

All right, the Science of Fluoride is coming up just after the break. She thinks her dress is why he wouldn't stop staring. She believes her lipstick is why he whistled at her. She thinks her shoes are why she was followed. It's not her dress, lipstick or shoes. Street harassment is never her fault. Learn how to safely intervene when witnessing street harassment

with the Stand Up Training. Stand Up Against Street Harassment by L'Oreal Paris with Right To Be. We're worth it. Get trained at standup-international.com. Welcome back. Today, we're looking at whether fluoride should be in our water or not. Is it safe or not? Meryl Hawn, PhD, is here with us. Hi, Wendy. Meryl, where do we begin? Is it safe or not? Meryl Horne, PhD, is here with us. Hi, Wendy. Meryl, where do we begin? Is fluoride a poison now? 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. Oh, God. How much fluoride did they dump in the water in that case? 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. Wow. Right. And at really high levels, it can stop your heart. 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.

The question obviously becomes, are the levels of fluoride that we're putting in the water safe? Yeah, that's the thing that everybody's fighting about with 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. But like 10 years ago, we checked to see how many kids in the US have this and it was 70%. 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. Okay. What about, the big thing 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's going on here? 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 Mallon, an assistant professor at the University of Florida. Floride. Got it. Yep. So, Ashley first remembers when she heard about this idea that fluoride might be bad for us.

She was with a family member. 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'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. And what about it felt kind of implausible? 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. Mm. Yeah. I hate that. 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. 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. Naturally.

Yeah. And some of those studies had been finding that people who lived in these areas had lower IQs. So at high doses, yes, but the question is, what about the low doses? Yeah, so that's what Ashley started looking into herself. But there were no studies on lower exposures really at that time. I was like, huh. 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 works. So they started following a couple hundred pregnant people and they were taking pee samples from them. And this way they could look at how much fluoride was in their pee. hundred pregnant people and they're taking pea samples from them and this way they could look at how much fluoride was in their pea. Okay. 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. 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.

It'll ask symptoms of autism, anxiety, depression, attention deficit, hyperactivity disorder, physical symptoms, so stomach aches, headaches, temper tantrums. 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. 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. 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. Uh-huh. And so what did they find? So Ashley was working from home looking at her data on her laptop when she saw the results. I'm like, oh my gosh, I want someone to check this to make sure this is real. Yeah.

Because what did you see? We found that higher levels of fluoride in pregnant women's urine was associated with more neurobehavioral problems in their children by age three. What kinds of problems? They did have more temper tantrums, they had more anxiety and symptoms linked to autism. Uh-huh. And can you put some numbers around this? I mean, when you say more tantrums, more anxiety, I mean, by how much? Well, it wasn't like, you know, every kid who had some fluoride in the water got anxiety.

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

Doubled odds. Nearly double. It was almost double. Yeah. Okay. It's intriguing. It's not a huge study, 200 people. Yeah.

It's funny. I thought that you would be way more surprised and alarmed at this study. That's how I felt when I saw this. There was a turning point for me where I was like, what? Fluoride might actually be doing something bad here? if I'm going to 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. And because I know the scientific status quo for so long has said, no, it's safe. So I can see myself looking for holes in this paper. It's not a randomized control trial.

So we can't say that the fluoride caused these differences. There might've been other differences between the groups. Um, so I, but what are other studies show here? Okay. So I found eight studies altogether that basically did what Ashley did. So they looked at prenatal fluoride exposure. Right. The pregnant women following pregnant women.

Yeah. Yeah. And looking at places with like not huge amounts of fluoride in the water, but Right, pregnant women, following pregnant women. And looking at places with 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. 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, 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. Yeah, huh. 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? Right. And a lot of those studies don't find any differences.

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? 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. 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 and 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. 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? No. And in general, IQs have been going up, like in places like the US. Hard to see that now. And like even one researcher who thinks that there is something here estimated that the difference between growing up in a community with fluoridated water and not is only the difference of two

and a half IQ points. So that feels like not that big a deal. And so where are you at with this now? Well I live in New York City and we do have fluoridated water here. Right. But like I haven't stopped drinking it. Like I'm not worried about it for my brain 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. Really? 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. It freaks me out now. Yeah.

So then what are you supposed to do if you're pregnant? Get a new water supply? I mean it's really hard, right? Because in theory, 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. Yeah, and then you've got to worry about the bloody microplastics with the hormone disruptors that we talked about last season.

I know. I think it's not perfect, but like, I would probably look into a filter. There's 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. 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. Yeah. For us big kids, coming out of the vagina, making podcasts, is there other stuff that we need to worry about? 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. Yeah. And there is some evidence that that stuff is real too, even at relatively low levels. Really? 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. Yes.

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 other studies haven't found those associations or one found that it was only significant if you also had an iodine deficiency to begin with. So what do we make of that as well?

What do you make of it? 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. Uh-huh. Reassuring.

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 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 okay to be basically forcing this many people to be having this chemical. Right. 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 has it taken so long? Is this kind of a failure 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. All right.

Well, this, this episode has taken quite the turn. Yeah. I mean, clearly fluoride is not the devil or poison as some people are claiming at the, you know, levels we put in our water. Um, but it really is frustrating that we don't have more science. as some people are claiming at the levels we put in our water. But it really is frustrating that we don't have more science on this, 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 you can pick a study that's saying the opposite. But what it does tell us though, the fact that for a lot of this stuff 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 basically all studies.

Yeah, that seems true. Okay, 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? That's after the break. Welcome back. Today we're talking about fluoride, Merrill. Any benefits to putting it in the water?

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 like, 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. So it's something like putting fluoride in the water had this big potential to make a huge difference because our teeth were so crappy, where now people say that like, well, we don't really need

to be doing that anymore because we have all these other tools in the toolbox to help our teeth. So are they right? I mean, does adding fluoride to the water, is it still preventing cavities or not? Well, now we actually have kind of a perfect opportunity to look at this, because as cities are taking fluoride out of the water today, we can see, okay, do the teeth actually get worse in places that do that? 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. When that all came out, it was just fascinating to me. Like, oh, we're not going to have fluoride in the water anymore. Isn't that interesting? And Lindsay and some of her public health 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. And like the hate mail came instantly. Like we got hate mail immediately. Saying what? Yeah. Oh, just like, you know, you guys are liars and you know, you're, you're fraudulent and I was like, oh, okay you guys are liars and you're fraudulent. And I was like, oh, okay, this is very interesting.

You're like, let's dive deeper into this field where I'm getting hit. 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. So, Lindsay was like, yeah, let's do some science here. open to some of the comments I was receiving. So Lindsay was like, yeah, let's do some science here. Like we're taking fluoride out of the water, will our teeth get crappier?

Yeah. 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 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 started by sending out teams of dental hygienists and researchers to schools in Calgary to check their teeth. So they were just all over the city, you know, for an entire year. 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 a science of tooth decay. And Lindsay's team wanted to make sure that the kids felt comfortable with this. In fact, the kids seemed to find it kind of fun. felt comfortable with this. In fact, the kids seemed to find it kind of fun.

And we'd have sort of groups of five kids come in at a time and be on deck. And they'd be dancing around. And 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. They were just walking around like they were so cool.

It's like a dance party. Yeah. Yeah, it was really cute. 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.

Listen, what did they find? You're stringing me along like floss here. Ha ha ha. 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? Yes. So what did they say?

So the prevalence of dental caries in Calgary. Yes. So what did they say? So the prevalence of dental caries in Calgary kids in their baby teeth was about 65%. Fluoride no longer in the water. 65% had cavities. All right. Drum roll. What is it when fluoride is in the water? That was compared to about 55% in Edmonton.

So like 10 percentage points different. Yeah, yeah. So that's the percent of kids that have any cavities at all. What did you think when you saw that data? This was larger than I expected. Okay. And what about other studies? So other studies generally find the same thing.

Kids do tend to get more cavities when they grow up without fluoridated water. Okay. Okay, so one thing that we've been told about fluoride, still true. Still good for our teeth. Yeah, these kids are getting fewer cavities and I know maybe you're thinking, who cares? A little cavity here or there, maybe it doesn't matter so much. Right, it's just their baby teeth, they're gonna get more? Well, it actually does matter.

So 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 we'd want to avoid putting kids through that. Yeah. 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 how bad their teeth were. Not all studies find this to be true, but Lindsay's does seem to be one of the best ones.

And so what about adults? Does it matter for us? find this to be true, but Lindsay's does seem to be like one of the best ones. And so what about adults? Does it matter for us? 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. Oh, it's tiny. Is that because we're better at brushing our teeth than kids?

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. Wow. Maximal hardness.

Yeah. That's an odd way to just describe anything to do with children. So yeah, it's like pretty convincing to me that fluoride in the water is still helping our teeth. Right. 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 after her studies came out, the town actually ended up voting on this and decided to

put fluoride back in the water. Whoa! They listened to the teeth science. They cared about their teeth. Yeah, it seems like it. Like they had a vote and 62% of the people said, yes, we want to fluoridate our water again. 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 type of thing. Oh, wow. Yeah. So this was quite a strong sign of support. Yeah.

So her study got a lot of attention, like even in the US. Here's some of that coverage. In Calgary, there was life before fluoride was removed from drinking water and life after. Children, mostly children, had to suffer so badly. So yeah, I asked Lindsay, like where she lands after all this. Should we be putting fluoride in the water? Yes, at recommended optimal concentrations.

And keep the research going. So don't cut research funding. That seems like a pertinent thing to say right now. Sure does. Sure does. All right. 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? 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. Hmm. Ooh, messy. I mean, zooming out here, you did speak to a lot of scientists in this space. What are they telling you when they put the risks and the benefits together here? Where do they stand?

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? 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, sorry,

I can't give you an answer. We need more research, which is kind of where I'm at. I just keep trying this over in my brain. I was just, so Meryl, do you think we should keep Florian in the water? I don't know. I am right there with him because I can really see it from both sides. I think what's so hard 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. Right. Right. What do you think? That's science versus 20 seconds of silence, is that about it? Okay, so Meryl, how many citations are in this episode? We had a lot. 105 citations. Whoa, 105. Wow. So before you send us angry emails,

Wow, so before you send us angry emails, Instagram messages, please have a look at our transcript. How could people find these 105 citations? 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. It's true. If you, on Instagram, we are science underscore vs. My TikTok is at wendyzookerman. Come say hello. Let us know what you thought of the episode. All right.

Thanks, Merle. Thanks, Wendy. This episode was produced by Merle Horn with help from me, Wendy Zuckerman, Rose Rimler, Michelle Dang and Akedie 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 Munger, 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 Lanphier, Professor Lok Do, Dr Maria Kippa, Professor Philippe Hejoul, Professor Steven Peckham, Dr Tommaso Filippini, and Professor Steven Levy. Besides Versus is a Spotify Studio's original, listen to us for free on Spotify or wherever you get your podcasts. 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 Zuckerman, back to you next time.