- Public water fluoridation has  been part of the discourse lately.

- Fluoride.

- Fluoride.

- [Speaker] Fluoride.

- [Speaker 1] Fluoride.

- Fluoride.

- I have always taken for granted that water  fluoridation is good and a huge win for public health.

But lots of people disagree with that  due to real research showing that high levels of fluoride in water can decrease IQ in young  children, and potentially be a neurotoxin.

Now, some of this argument takes place in the  media, and a whole bunch of it takes place in the scientific literature.

So I wanna avoid  the shouting, and get to the real information, because very truthfully and honestly, I  wanna be able to be an informed participant in these conversations.

I spent five years  getting a degree in doing my own research, so might as well put it to work.

Today is my  first big research gathering day.

And so what I'm doing is I'm trying to go through my outline  and figure out what papers are gonna help me answer all these questions.

How do I wade into  this as a bold science communicator and decide that I'm gonna absorb and comprehend decades of  research in three weeks?

So I'm not going to, right?

But that also means today I'm trying to  figure out who are the fluoride researchers that I'm trying to talk to.

And I think it's hard to  do sometimes.

The media can fall into the trap of just picking one person on each side of the debate  and putting them against each other.

And we know that sometimes can give the public a false idea  of how the underlying scientific community feels about a topic.

I sat down and I thought about what  I knew, and what I didn't know about fluoride.

And I came up with seven big questions that I want  to answer.

We'll start with, what does fluoride do for your teeth?

Fluoride works to protect your  teeth in three ways.

It reduces demineralization, it promotes remineralization, and it inhibits  bacterial growth.

When you drink fluoridated water, or brush with fluoridated toothpaste,  fluoride ions wind up in the biofilm on your teeth.

From there, they travel with bacterial acid  into the crystal structure of the enamel, where they replace a hydroxyl group on hydroxyapatite  to become fluorapatite.

Fluorapatite is much more resistant to acid, and can keep your tooth enamel  strong.

Same with these two eggs.

I smeared this one in fluoridated toothpaste for a day, and left  this one alone.

And when I cover them in vinegar, you can see that the fluoride treated egg is much  more resistant to the acid breakdown than the not treated one.

In a 2015 meta-analysis that looked  at 155 studies found that water fluoridation reduces caries, basically tooth decay, by 35% in  primary teeth, and 26% in permanent teeth.

In the 1940s, Grand Rapids, Michigan, started adding  fluoride to their tap water after researchers in the early 20th century discovered two things.

One, that children who grew up in towns with high levels of fluoride in their water often  suffered from dark brown modeling on their teeth, now called fluorosis.

And two, that those same  children had almost no dental cavities.

The levels of fluoride they added were titrated to keep teeth  healthy, while reducing fluorosis risk.

And over the next 15 years, the incidence of cavities in  children born after fluoridation dropped by 60%, making tooth decay a preventable disease for the  first time in history.

Fluoride in water works to prevent dental decay.

That is not what's in  question in public debate.

But what is in debate is if water is the best delivery method for  it.

So is there a difference between ingestion and topical application for dental health?

Most  results point to the idea that fluoride is most effective topically.

So if we can brush with it,  swish with it, chew it, that seems to be the most effective.

Did you ever have those fluoride rinse  days at school?

Or have to sit for 60 seconds with fluoride trays in your mouth?

These are other  strategies that modern dentistry uses to get that fluoride.

I hated those trays, though.

They  always made me feel like I couldn't breathe.

But the thing is, modern dentistry is really different  from dentistry in 1945 when adding fluoride to water began.

Fluoride-containing toothpaste and  mouthwash is in basically every grocery store.

And while access to dental care isn't perfect, because  why are my special face bones not covered by my normal health insurance?

Dental care is certainly  more widespread.

So do we really need to be adding fluoride to water in 2025?

In fact, this review,  are you a meta-analysis or a review?

People will be grumpy.

This is a review.

There was even a  review from 2024 that found that while community water fluoridation seemed to lead to a greater  reduction in dental caries in kids, it potentially had smaller effect sizes than in pre-1975 studies,  back before dental care was what it is now.

So what happens if we start taking fluoride out of  places where we've added it?

I was just driving to the grocery store, and it's rare that I get  to work on a story that is so topical.

There was a story on NPR about a city council member  from Calgary talking about how when he was first elected about 10 years ago, they removed fluoride  from the water, and then they saw an increase in the incidence of dental caries, and now the  residents wanted the fluoride back.

Gonna go look at the sources.

The study found a significantly  higher rate of dental caries, especially in primary teeth in kids in Calgary.

A local hospital  also saw that the number of dental infections in children that were so bad that they required IV  antibiotics for treatment also increased by 700%.

Calgary voted to start adding fluoride back  into their water in 2021.

2025, we still have evidence that adding fluoride to water decreases  dental decay.

So why is there any question about fluoride in water?

It's because over the past  two decades, a number of studies have shown that children exposed to high levels of fluoride  during development have lower IQs.

So this goes back to one of my original questions.

Does  fluoride have neurological effects at community water fluoridation levels?

One of the most high  profile, which sparked a lot of controversy, was a study also out of Canada.

It used a dataset  called MIREC, which looked at environmental exposures during pregnancy.

The researchers looked  specifically at fluoride, and they looked at both a subset of women who had given urine samples, and  a subset of women who had self-reported fluoride exposures during pregnancy.

They compared these to  children's IQs at ages three and four.

They found that higher fluoride exposures during pregnancy as  measured by urinary levels, were related to lower IQ in boys.

And as measured by self-reported  consumption studies, higher fluoride intake meant lower IQs in all children by about three to  four IQ points.

The authors and proponents of this study suggested that pregnant people should watch  their fluoride consumption, and that baby formula should be made with non-fluorinated bottled  water.

There have been some strong criticisms of this paper for things like how they measured  maternal fluoride exposure using urine samples, and for how they address the results to the  public.

And this got personal and heated.

There were letters sent calling for resignations,  and knowing all of that, when I read this paper, my reaction was kind of like, "Oh, that's it?"

This felt like an interesting result that should be followed up on, but not the giant smoking gun  that the media and literature war seems to make it out to be.

I mean, look at these graphs.

Sure,  there is an association here, but it doesn't seem damning.

And especially considering that the  maternal exposure on the right was estimated using things they knew about the mothers and  their habits, not directly tested, it just seemed kind of overblown.

Should more research be  done to follow up on this?

Absolutely.

But for me, this study was just kind of like a, "Okay, that's  interesting result."

It wasn't like, "Whoa.

Whoa."

But the MIREC study is not the only study  that is found in association between higher fluoride levels and lower IQ.

In mid-2024,  the National Toxicology Program released an initial analysis of 74 studies that looked at  fluoride exposure and children's IQs, and found "a statistically significant association between  higher fluoride exposure, and lower children's IQ scores, showing that the more fluoride a child  is exposed to, the more likely that child's IQ will be lower than if they were not exposed."

Community water fluoridation in the United States is currently recommended to be 0.7 milligrams per  liter, or 0.7 parts per million of fluoride in water.

The optimal range used to be 1.2 milligrams  per liter in some parts of the US.

Colder places, where they assumed you might drink less water,  had a higher recommended level of fluoride than hot places, where they assumed that you would  drink more water.

But we're now at 0.7.

The World Health Organization recommends a standard  of 1.5 milligrams per liter.

The studies in the NTP monograph I just mentioned looked at many  communities whose fluoride levels were much higher than this in the 1.5 milligram per liter levels,  due to naturally occurring fluoride in the water.

Also, most of these studies were performed outside  of the US with many of the studies occurring in China, India, and Iran and other international  locations.

The NTP reports specifically said that it could not make conclusions about the safety  of community water fluoridation, but instead was focused on the risks of high fluoride levels.

From  this data, it seems pretty clear that high levels of fluoride in water could negatively impact IQ  levels in children.

The scientific article version of this paper came out in JAMA Pediatrics on  January 6th, along with two editorials commenting on it, one positively, and one negatively.

I  always know going into these things, that I'm gonna have to read more research than I think I'm  gonna have to read.

But this really was sliding in at the 11th hour.

The main article breaks apart  the 74 studies into ones that they considered to have high bias and ones that have low bias,  which is their way of classifying how rigorous, and yes, biased, or unbiased a study is.

What  I wanted to know was what the high-quality, low-bias study said about fluoride levels below  1.5 milligrams per liter.

And the abstract said, "Among the subset of low risk-of-bias studies,  there were inverse associations when exposed groups were restricted to less than four  milligrams per liter, less than two milligrams per liter, and less than 1.5 milligrams per  liter for analyses of fluoride measured both in water and in urine."

Which makes it sound like  there were adverse effects below 1.5 milligrams per liter in water levels.

But if you go look at  the three studies that met those qualifications, the association is not statistically significant.

It's really frustrating that these studies are mostly looking at water fluoride levels far above  what we add to water here in the United States.

So I feel the need to document that this is  how I'm spending my Sunday night.

Internet with chips and guacamole and science papers.

For you, Internet.

For you.

"To our knowledge, no studies of fluoride exposure in children's IQ  have been performed in the United States."

They say in here that this was not designed to address  the broader public health implications of water fluoridation in the United States.

But that's not  how it's being reported in the media.

Why?

Why have we done this in Canada and in Mexico, and in  all of these other places and not here?

Is there just that nobody wants to fund it?

And it's like  a big, annoying study to do?

Is it really that like we just didn't realize until recently  that this was something we should do?

Yeah, I don't know.

I'm frustrated.

I'm gonna add what  I think is an important note here.

That there are about 2.9 million people in the US living in  communities where water fluoride levels do exceed WHO recommended levels above 1.5 milligrams per  liter due to natural groundwater fluoride.

Now, these studies indicate to me that we do need to  be talking about how to lower fluoride levels in those communities.

That feels like a public  health initiative that could do some meaningful good based on these results.

But that is not what  any of the headlines or arguments are actually talking about right now.

Part of the problem  is that these studies are observational, not experimental.

But all of this left me with even  more questions.

First of all, do a few IQ points here or there even matter?

On a person-to-person  level, probably not.

But on a population level, maybe.

How reliable also is testing a child's IQ?

How do we compare studies that are looking at all different levels of fluoride exposure?

Many  are using different methods of testing IQ or cognition, and almost none of them are looking  directly at the IQ effects on communities here in the US who are exposed due to community  water fluoridation.

And again, that was really frustrating to me.

And I spent a lot of time on  Google Scholar, trying to find something like this.

A big longitudinal perspective study of  the effects of community water fluoridation on IQ levels in children in the US.

And it's not  really out there.

Now, some people have tried similar things.

For example, a paper published  in December of 2024 looked at Australians, who have a similar water fluoridation program to  us.

They looked at adults who had been exposed, or not, to community water fluoridation under the  age of five, and found no connection between adult intelligence and fluoride exposure.

Now, the N is  small here.

It is under 400 people.

But they just found no difference.

Like these are some of the  most boring graphs you have ever seen.

Just like, nada.

There was also a study that followed people  in New Zealand for 38 years that found similar results.

No dramatic historical decreases in IQ  have been seen following widespread implementation of community water fluoridation, or worldwide  introduction of fluoride toothpastes.

Instead, historical comparisons of documented substantial  IQ gains across country since the mid-1900s.

We've been doing community water fluoridation.

We've  been giving people fluoride in their toothpaste.

People drink tea a lot.

And we just don't see a  dramatic, like people didn't just get stupider.

Like all jokes aside, it's not like we started  community water fluoridation and everyone just got less intelligent.

There's no data to suggest  that.

But I'm gonna be honest at this point, that I am exhausted.

I've been doing this for  weeks now.

Most people do not have jobs that let them do stuff like this.

We cannot all be  doing all this reading.

We have other jobs to do, and other issues that we need to be informed  on.

And these are just the highlights of this research.

And I know, down in the comments, you're  gonna tell me that I missed your favorite paper, or your favorite piece of data on this.

But this  video cannot be three hours long.

Producer Elaine will kill me.

So I asked some experts.

How do  you balance the positive dental health benefits of fluoride with potential negative mental health  benefits?

The predominant sense is that we need to be doing a risk-benefit analysis here.

Most  people felt that fluoride is beneficial for dental health, and that keeping some level of  it in tap water has protective dental health benefits for kids here in the US.

But that  fluoride can be neurotoxic at high levels, especially in places where it's naturally  occurring in groundwater, but that the data suggests it's not a problem at levels currently  recommended in the US.

Risk-benefit analysis.

The dose makes the poison.

That is what I  have landed on in this whole conversation.

Fluoride is bad at super high levels, but it's  necessary and even protective at low ones.

We need better data to make a conclusive statement  about where the dose that's beneficial dentally, but not detrimental cognitively lies.

And based on  all of this, I think the data points to the fact that we seem to be pretty close to it with our 0.7  milligrams per liter level.

I think that we should keep community water fluoridation at the current  levels.

But this is my personal opinion.

It is not one of any organization.

I am not a public health  official.

I am just someone trying to be really informed about this issue, and feel confident in  how I talk about it, and how I vote on it and all that kind of stuff.

I do, however, also think  that we need longer-term, bigger observational studies in the United States of whether or not  community water fluoridation at our levels, in our communities, has any effect on IQ.

I hope this  was helpful.

Please don't send me death threats.