Show Notes
A follow up Q&A to this week’s fluoride deep dive. Dr. Ravi Kumar picks five of the most thoughtful listener questions and does a mini deep dive on each, tying together the key themes from the full episode and filling in the practical gaps so you can make decisions for your own family.
If you listened to the fluoride deep dive earlier in the week and walked away with more questions, this is the follow up. Dr. Kumar works through why the American Dental Association still recommends fluoridation even as recent rulings and reviews move the other way, what a pregnant woman drinking municipal tap water should actually do about it, how to think about the fluoride varnish your pediatric dentist wants to apply at every visit, whether nano-hydroxyapatite toothpaste is safe given the fears around the word “nano,” and whether bottled water is a reasonable substitute for installing a reverse osmosis filter at home. Throughout, he keeps coming back to the same theme: read the data yourself, weigh your own family’s risk, and remember that this is your informed consent to give.
In this episode, you will discover:
- Why the ADA still recommends fluoridation: Large medical and dental organizations move very slowly, and their positions reflect the science as it was understood 5, 10, or 20 years ago. The ADA’s stance is essentially unchanged since the 1950s Grand Rapids data, while the 2024 Cochrane Review, the 2024 federal toxicology analysis, the 2025 JAMA Pediatrics meta-analysis, and the federal court ruling all landed in the last 18 months. Reversing a 75-year-old policy is also a reputational and political decision, not just a scientific one
- Outdated authority is still outdated: The same institutional lag showed up with proton pump inhibitors, hormone replacement therapy, and dietary fat recommendations. Advice from an authority does not override the actual peer-reviewed studies published in the last two years
- Pregnancy is the most concerning scenario: A 2017 Mexican cohort linked higher maternal urinary fluoride to lower childhood IQ, and a 2019 JAMA Pediatrics study found the same in Canadian women drinking water at the same “optimally fluoridated” levels used in the United States, with effects measured in their children at ages 3 and 4
- The mechanism makes biological sense: Fluoride crosses the placenta and the blood brain barrier, and the developing fetal brain is uniquely vulnerable to neurotoxins, the same logic we already accept for mercury, lead, and alcohol. If you are pregnant and on city water, a reverse osmosis filter under the sink (a couple hundred dollars) or bottled water for drinking and cooking is the cautious move
- Fluoride varnish actually has good evidence: A 2013 Cochrane review of 22 trials found varnish reduces decay by about 43% in permanent teeth and 37% in baby teeth, a bigger effect than toothpaste because the concentration is higher and the application is professional
- But varnish adds to the cumulative dose: It is a high concentration topical exposure that absorbs through the oral mucosa and any swallowing. For a child already getting fluoridated water, toothpaste, and processed foods, twice-a-year varnish is a meaningful addition
- Risk stratification is the right frame: For a high cavity risk child (prior cavities, poor enamel, strong family history), the benefit may outweigh the exposure. For a low risk child who brushes well, eats low sugar, and uses hydroxyapatite toothpaste, the marginal benefit is small. Ask your dentist to articulate your child’s specific cavity risk, and remember you can politely decline
- Why nano-hydroxyapatite is safe despite the “nano” fear: Hydroxyapatite is what your bones are made of, so anything absorbed is biologically identical to a major component of bone, breaking down into calcium and phosphate your body uses constantly. It has been used in Japanese toothpaste since the 1970s and by NASA for roughly 50 years
- The regulators agree: The European Scientific Committee on Consumer Safety reviewed nano-hydroxyapatite in 2023 and judged it safe in oral care up to 10% (since adjusted upward), specifically for the rod-shaped particles all commercial products use. Look for 10% as the active ingredient on the label
- Bottled water is a legitimate shortcut: A 2009 General Dentistry analysis of 150 bottled waters found distilled averaged under 0.01 mg/L and drinking/purified under 0.03 mg/L, versus 0.7 mg/L in tap water. The USDA puts the bottled average near 0.11 mg/L, about a seventh of tap, though some brands are just repackaged fluoridated city water, so read the label
Key Takeaways
- The strongest reason the ADA has not moved is institutional lag, not new evidence in fluoride’s favor. The court ruling and major reviews are all less than two years old, and dogma always moves slower than the data
- Pregnancy is where the data is most concerning and least worth being passive about. If you are pregnant and on municipal water, switch to reverse osmosis or bottled water for drinking and cooking now
- Fluoride varnish works, but the decision should be risk-stratified. Make your dentist name your child’s actual cavity risk before you agree to routine application, and know that declining is your right
- Nano-hydroxyapatite is one of the most well studied fluoride alternatives. It is bone-identical, breaks down into calcium and phosphate, and is endorsed by one of the world’s most cautious regulators. Look for 10% on the label
- Bottled water removes most of your daily fluoride dose and is a reasonable interim solution, but reverse osmosis at home is cheaper over time, avoids microplastics, and gives you control over the source
- A standard Brita-style carbon filter does not remove fluoride. Reverse osmosis is the gold standard
Episode Resources
If you have not yet listened to this week’s main episode, Fluoride Science: Neurodevelopment Risks, Thyroid Function, and Water Filtration, start there. This Q&A builds directly on those concepts.
Transcript
[00:00 –> 00:22] Dr. Ravi Kumar: Hey, everybody. Dr. Kumar here. So I knew the fluoride episode that I did earlier this week was gonna pique some interest. And I got a lot of really thoughtful questions. So I picked five of them that I thought would tie together a lot of the information I presented earlier in the week, and help you with some practical application of this knowledge. So let’s get into it.
[00:22 –> 01:09] Dr. Ravi Kumar: Okay. First question. If the data is so questionable, why does the American Dental Association still recommend fluoridation? So this is a good question. The simple version is that large medical and dental organizations move very slowly. And their positions reflect the science as it was understood 5, 10, sometimes 20 years ago. In this situation, the ADA position on water fluoridation is essentially the same position that they have held since the 1950s, when the original Grand Rapids data was the only data we had. The 2024 Cochrane Review, the 2024 federal toxicology analysis, the 2025 JAMA Pediatrics meta-analysis, and the federal court ruling all happened in the last 18 months. That is not enough time for a national organization to update a 75-year-old policy position.
[01:09 –> 02:05] Dr. Ravi Kumar: There is also a structural issue here. When an organization has spent decades publicly defending a policy as one of the greatest achievements of public health, reversing course is not just a scientific decision, it’s a reputational and political one. This is not unique to dentistry. We saw the same lag with proton pump inhibitors, with hormone replacement therapy, with dietary fat recommendations. Medical dogma always moves slower than the data. That’s why I keep coming back to the same theme on this show. Don’t outsource your thinking to organizations. Read the data yourself and make informed decisions for your own family. The ADA’s position will likely move as more data comes in and public sentiment changes. But it’s important to remember that outdated advice from an authority is still outdated advice, and it does not override the actual peer-reviewed studies that have been published in the last two years on this subject.
[02:05 –> 03:05] Dr. Ravi Kumar: Okay. Next question. I’m pregnant, and I drink municipal tap water. Should I be doing something differently? So the answer to your question is yes. In fact, the pregnancy data is the most concerning part of this entire conversation on fluoride, and it’s not one I would recommend being passive about. There are two studies you should know about. The first was published in 2017, looking at a Mexican cohort of mothers and children. Higher maternal urinary fluoride during pregnancy was associated with lower IQ scores in their children measured years later. That data alone would not be enough to change practice. But then in 2019, a study was published in JAMA Pediatrics looking at a Canadian cohort. The Canadian women in this study were drinking water at the same fluoride levels we use in the United States, which is called optimally fluoridated water. The researchers still found that higher maternal fluoride exposure during pregnancy was associated with lower IQ scores in their children at ages 3 and 4.
[03:05 –> 04:04] Dr. Ravi Kumar: The mechanism makes biological sense. Fluoride crosses the placenta, it crosses the blood brain barrier, and the developing fetal brain is uniquely vulnerable to neurotoxins during pregnancy. We accept this with mercury, with lead, with alcohol, and there’s emerging evidence that suggests we may need to accept it with fluoride too. The practical takeaway, if you’re pregnant and on city water, get a reverse osmosis filter under your kitchen sink. They cost a couple hundred dollars, and remove fluoride along with other contaminants. Use that water for drinking and cooking. This is one of those situations where I would rather you act on incomplete evidence and be overly cautious than go the other way and have been wrong. So if you can’t get an RO system, drink bottled water. Drink it in the larger jug, so there’s less plastic exposed to more water, and you should be fine. But an RO system is the gold standard for removing fluoride. The Brita filter that most people have won’t do it.
[04:04 –> 05:06] Dr. Ravi Kumar: Okay. Next question. My pediatric dentist wants to apply fluoride varnish to my kids’ teeth at every visit. Should I let them? This is a personal question that we all need to answer for ourselves based on our own view of the literature. But fluoride varnish at the dentist actually has solid evidence behind it. A 2013 Cochrane review of 22 trials found that varnish reduces decay in permanent teeth by about 43%, and in baby teeth by about 37%. That is a real effect, and it’s bigger than fluoride toothpaste because the concentration is much higher and the application is professional. But here’s the trade off and the risks that you need to know about. Fluoride varnish is a high concentration topical exposure. Some of that fluoride will absorb through the oral mucosa, and through any swallowing that happens during or after the application. For a child who already drinks fluoridated water, brushes with fluoride toothpaste, eats fluoridated processed foods, and now gets varnish twice a year, the cumulative dose is meaningful.
[05:06 –> 06:07] Dr. Ravi Kumar: My honest thinking on this is about risk stratification. If your child has high cavity risk, meaning they’ve already had cavities, they have poor enamel quality, or there’s a strong family history, the cavity prevention benefit of varnish may outweigh the additional fluoride exposure. If your child has low cavity risk, brushes consistently, eats a low sugar diet, and uses hydroxyapatite toothpaste at home, the marginal benefit of varnish is much smaller, and skipping it seems reasonable to me. That’s what we do for our kids. We don’t let them get the fluoride varnish. So the practical takeaway is this. This is a conversation you have to have with your pediatric dentist, who’s likely gonna push for fluoride treatment. Ask them what your child’s cavity risk actually is. If they can’t articulate the specific reason your child needs varnish beyond it just being a routine thing that they do, you have permission to politely decline. It’s your informed consent, remember, so you can decide whether they get it or not.
[06:07 –> 06:53] Dr. Ravi Kumar: Okay. Next question. I keep hearing that nano-hydroxyapatite particles can absorb into the bloodstream. Is the toothpaste really safe? So this is a great question, and one that a lot of people are bringing up, because the word nano makes everyone nervous, and for good reason, because nanoparticles are extremely small and they can sometimes pass through biological barriers. But let’s first get this out in the open. Hydroxyapatite is what your bones are made of. So if it gets into your bloodstream, it’s biologically identical to a major component of your bones. So with that said, here’s what the evidence actually shows. Nano-hydroxyapatite has been used in toothpaste in Japan since the 1970s, and has been used by NASA with no risks after 50 years of use, basically.
[06:53 –> 08:03] Dr. Ravi Kumar: The European Scientific Committee on Consumer Safety, which is one of the most cautious regulatory bodies in the world, formally reviewed nano-hydroxyapatite in 2023 and concluded that it’s safe in oral care products at concentrations up to 10%. And recently, they’ve adjusted that upward as well. And they specifically stated that particles that are rod shaped are safer, which is what all commercial dental products use. So the mechanistic reason that this is safe is straightforward. Even if a few nanoparticles were absorbed, hydroxyapatite breaks down into calcium and phosphate, two compounds that your body uses constantly. There’s no exotic foreign substance accumulating anywhere. Compare that to fluoride, which crosses the blood brain barrier and the placenta, accumulates in the bones over a lifetime, and behaves very differently inside the body than it does on the surface of the tooth. So I think the practical takeaway here is that nano-hydroxyapatite is one of the most well studied fluoride alternatives available. The concentration that you want on the label of a toothpaste that’s using nano-hydroxyapatite is 10%. So just look for that as the active ingredient.
[08:03 –> 08:53] Dr. Ravi Kumar: Okay. Next question. Can I just drink bottled water instead of installing a filter? Yeah, this is good, and we talked about it just a little bit ago. Yes. In most cases, bottled water is generally low in fluoride, and the data is pretty clear on this. A study published in General Dentistry in 2009 analyzed 150 different bottled waters across multiple categories. Distilled bottled water averaged less than 0.01 milligrams per liter of fluoride. Drinking and purified bottled waters averaged less than 0.03. Compare that to tap water, which is 0.7 milligrams per liter of fluoride. And you can see why bottled water effectively removes most of your daily fluoride dose. The USDA national database puts the average fluoride content of bottled water around 0.11 milligrams per liter, which is a seventh of what is in tap water.
[08:53 –> 09:43] Dr. Ravi Kumar: The catch is that not all bottled waters are the same. Some bottled water is just repackaged municipal tap water from fluoridated cities. And a small percentage of brands actually have fluoride levels near fluoridated water supply levels. So you need to read the label or contact the company. Spring water, mineral water, distilled water, and reverse osmosis purified bottled water are typically your safest bets. That said, I personally think reverse osmosis at home is the better long term solution. It costs less than two years of bottled water for a family. It eliminates the plastic waste and the microplastic exposure from bottled water, which is on its own an emerging concern, and you have control over the source. But if bottled water is what’s accessible to you right now, especially during pregnancy, it is a reasonable solution.
[09:43 –> 10:06] Dr. Ravi Kumar: So that’s it for this week, folks. I hope this filled some of the practical gaps from the main episode, and gives you what you need to make decisions for your own family. As always, none of this is medical advice, so take this information, ask better questions, and work with your own healthcare provider to figure out what makes sense for you. Okay, folks. Cheers, and I’ll see you next week.