In today’s newsletter, we’re breaking down the study that claimed xylitol is bad for your heart, why the science doesn’t hold up, and what decades of real research say instead.
And pregnant moms—don’t miss the tip at the end. It’s one of the most powerful (and easy) ways to protect your baby’s future oral health.
Since that study came out last year, I’ve received hundreds of questions like:
“Isn’t xylitol bad for your heart?”
“Should I stop using xylitol toothpaste?”
No surprise people are still confused—when weak science gets paired with sensational headlines, it creates a lot of fear.
Here’s why that study was deeply flawed, poorly designed, and irresponsibly reported:
1. The study didn’t exclude people with existing heart disease—in fact, 46% of participants already had it. That’s a massive red flag, because it blurs the line between correlation and causation. Was xylitol the issue… or just a byproduct of poor metabolic health?
2. In mice, the researchers used extremely high doses of xylitol—equivalent to over 30 grams in a single sitting for a human. That’s far beyond typical use and would likely cause diarrhea and GI upset before anything else. The study bypassed normal digestion too, using direct injection, which doesn’t reflect how humans consume xylitol.
3. The study also didn’t control for sugar intake—a major oversight, since dietary sugar is a well-known driver of cardiovascular disease. Without accounting for that, how can we know whether xylitol was actually the problem—or just a bystander?
4. The study explicitly states that its findings don’t apply to xylitol used in oral care—but you wouldn’t know that from the headlines. Media coverage failed to mention this crucial detail, leaving people afraid of the very ingredient that protects their teeth.
This wasn’t a randomized controlled trial—the gold standard in clinical research. It was an observational study, with so many uncontrolled variables that its conclusions are, frankly, unreliable.
When this study first came out, I took it seriously. The claims were alarming, and I wanted to understand whether there was anything new I needed to reconsider. But once I dug into the actual data, it was clear the science didn’t hold up. The study design was weak, the conclusions were overstated, and it ignored decades of solid research showing xylitol’s clear benefits.
What evidence do we have on xylitol?
1. Xylitol has been studied since the 1970s, particularly in Scandinavia, where it was first evaluated in public oral health programs.
2. Landmark trials like the Turku Sugar Studies (Finland, 1970s) were among the first to show that replacing sucrose with xylitol dramatically reduced caries incidence. It was one of the first large, long-term human studies to show that xylitol could reduce cavities even better than just cutting back on sugar.
3. A 2015 Cochrane Review analyzed data from 10 studies and found consistent evidence that xylitol-containing products reduced cavity-causing bacteria and dental caries risk—especially in children.
4. The European Food Safety Authority (EFSA) allows xylitol to carry the health claim: “Chewing gum sweetened with xylitol helps reduce the risk of tooth decay.”
5. For the pregnant moms reading, this one is incredible: Xylitol has been included in maternal oral health protocols to reduce early colonization of cariogenic bacteria in infants.
Xylitol is one of the most well-studied ingredients in oral health. Not only is xylitol safe—it’s effective. Research consistently shows it reduces Streptococcus mutans, lowers oral acidity, and supports remineralization by stimulating saliva flow. That’s why it’s in Fygg, the toothpaste I formulated along with my co-founders.
And, it’s worth asking—why would an ingredient with a strong safety record and decades of research behind it suddenly come under fire? Especially one that replaces sugar, improves metabolic health, and isn’t easy to profit from at scale 🤨
Have you had someone tell you to stop using xylitol? Forward them this email. And if you’ve noticed improvements since switching to xylitol toothpaste or mints, hit reply—I’d love to hear your story.
Mark
P.S. Speaking of incredible, science-based ways to improve your oral health…this newsletter is sponsored by my favorite magnesium supplement which I recommend to 99% of my patients. If you’re looking for a highly absorbable, full-spectrum option to support sleep, mood, and muscle recovery, THIS is my go-to.
P.P.S. I know your inbox is full, and it means a lot that you’ve made it all the way to the end of this email. I hear from hundreds of you each week—and while I can’t reply to every message, I do read each one. Your questions, your stories, your feedback—they shape the work I do. So if you’ve ever hit reply, thank you. And if today’s message helped you feel a little more informed or empowered, that’s exactly why I do this.