Everyone’s talking about Ozempic. But almost no one is talking about this: You might already have your own version of it—and it might be breaking down because of something as simple as your mouthwash.
In this newsletter, we’re unpacking how your mouth—not your stomach, not your weight, not your willpower—could be sabotaging the hormone that controls hunger, energy, and metabolism.
In the age of injectables, GLP-1 has become shorthand for thinness, appetite control, and metabolic rebirth. Originally studied for its role in diabetes, this gut hormone is now the molecular star behind drugs like Ozempic and Wegovy. It makes you feel full. It slows digestion. It even tweaks the reward centers of the brain.
But here’s what most people don’t realize: your body already makes GLP-1 on its own. And it does it with help from bacteria. No surprise there, the “good guys” of your microbiomes are always responsible for the good stuff!
The breakthrough came in 2012, when researchers at the University of Cambridge published a study in the journal Diabetes. Their finding: short-chain fatty acids—byproducts of fiber fermentation by gut bacteria—can directly trigger GLP-1 secretion through a receptor called FFAR2 (Tolhurst et al., 2012). In other words: Your microbes help control your hunger.
There’s big money in mimicking GLP-1. Novo Nordisk and Eli Lilly have built multi-billion-dollar pipelines around it.
But what if we could coax the body to produce more of it naturally? That question is now driving new research in nutrition and microbiome medicine.
Several human studies have already shown this: when people eat more fermentable fiber—like inulin, found in leeks and Jerusalem artichokes—their gut bacteria produce more short-chain fatty acids (SCFAs). These are chemical messengers that help regulate appetite and metabolism.
The SCFAs then signal your body to make more GLP-1 (the same hormone that Ozempic mimics) and another one called PYY, which also helps you feel full.
There’s a catch, though.
It doesn’t always work, especially if you use antibacterial mouthwash (yes, including your “natural” mouthwash with essential oils).
We’ve always blamed the gut. But what if the problem starts higher up? That’s where the mouth comes in…
We’ve long treated the mouth as a separate system. But it’s the beginning of the gastrointestinal tract—and the microbes in your mouth don’t stay put.
A disrupted oral microbiome—meaning the balance of bacteria in your mouth is off—can throw the whole system out of sync. This kind of imbalance (called dysbiosis) can happen from daily use of antiseptic mouthwash, untreated gum inflammation, or a lack of microbial diversity.
When that balance is off, you end up seeding your gut with the wrong bacteria. That shift can lower SCFA production and block GLP-1 release.
You’ve heard me say this over and over—oral health isn’t just about teeth. It’s about inflammation, blood sugar, hormones, everything. And the research is finally catching up. Not just cavities or gum disease—but how your mouth sets the stage for microbial balance throughout the entire gut.
We’re still in early days. No one’s suggesting you can reverse type 2 diabetes with floss and a salad (although there is some basis for that! We can discuss in a future newsletter…)
But consider this: In one human study, researchers skipped the fiber and delivered SCFAs—the compounds your gut bacteria normally make when they ferment prebiotic fiber—straight into the colon. Even without fiber, this increased GLP-1, improved insulin sensitivity, and lowered how much people ate (Chambers et al., 2015).
In another study, people ate a fiber-enriched bar. But it only worked for participants whose microbiomes could actually turn that fiber into SCFAs. If their bacteria weren’t capable of fermentation, they saw no benefit (Sanchez-Tapia et al., 2020).
That’s the key: your body can only make GLP-1 from fiber if the right microbes are present.
And those microbes? In the digestive tract, they’re first found in your mouth.
When your oral microbiome is healthy, it helps populate your gut with the kinds of bacteria that can ferment fiber into SCFAs. These microbes don’t just pass through; they take up residence and influence the microbial makeup of your gut (Segata et al., 2012).
But when your oral microbiome is disrupted—by daily antiseptic mouthwash, chronic inflammation, or poor oral hygiene and low pH (mouth breathing)—you send the wrong microbial signals downstream. That can reduce your gut’s ability to produce SCFAs, no matter how much fiber you eat.
This isn’t just “eat more fiber, feel full.” It’s a microbial chain reaction. And it starts in your mouth.
So yes, fiber matters. But the real takeaway is this: your mouth sets the tone for your metabolism.
What am I supposed to do, then, Dr. B?
Beyond fiber, certain compounds help support a healthier oral microbiome:
- Polyphenols (like those in green tea, berries, and olive oil) help inhibit pathogenic bacteria while supporting beneficial strains. I drink green tea every morning!
- Nitrate-rich vegetables—like beets, spinach, and arugula—fuel nitric oxide production, which helps regulate microbial balance.
- Vitamin D supports immune function and oral tissue integrity, helping maintain a stable microbial environment.
- Magnesium works alongside vitamin D in the body—it helps activate vitamin D and supports balanced immune and inflammatory responses. That kind of systemic support is critical for maintaining a resilient oral environment where beneficial microbes can thrive. (There are many forms of magnesium out there, which is why I take a blend of seven types + cofactors to ensure proper absorption—link to the one I swear by)
I think of these as reinforcements: they don’t replace fiber, but they help the right bacteria thrive.
By now, you’re probably wondering: what do I actually eat to support this?
Here’s what I eat: leeks, Jerusalem artichokes, raw garlic. These are rich in prebiotic fibers like inulin and resistant starch—and they feed the right microbes in the mouth and gut.
I even built a breakfast around this idea. I call it Dr. B’s Microbiome Omelet—it’s delicious and feeds my oral microbiome.
When you combine those foods with an oral care routine designed to preserve microbial diversity—like using Fygg toothpaste (code ATD15), skipping antiseptic mouthwash, and gently tongue scraping and mouth taping for those who need, and I’m one of those people—you create the right environment for those microbes to do their job.
You’re not just supporting digestion. You’re laying the foundation for appetite regulation, hormone balance, and better energy.
If you want to support your body’s own GLP-1 production…
- Stop killing 99.9% of your oral bacteria.
- Start feeding the ones that matter—with prebiotic foods, not mouthwash.
- Rebuild your gut’s ability to ferment fiber.
- Think about the whole axis: mouth → gut → brain → appetite.
Yet another example of how the bugs in the mouth are at play in so many different ways!
This is something functional dentists concern themselves with—unfortunately there are very few of them, but I aim to change that with my new online CE course, Foundations of Functional Dentistry—if you’re a dentist or hygienist who’s interested, hit reply and my team will get you on the list.
If you’ve read this far, thank you. I know your inbox is full, and I appreciate your curiosity and care about oral health.
I’d love to hear what you thought of this newsletter—and what you’d like me to explore next. Just hit reply.
If you want more:
- Read: Heal Your Oral Microbiome by Cass Nelson-Dooley
- Listen to the podcast: Ask the Dentist Podcast
- Find a functional dentist: Functional Dentist Directory
- Know a dentist who practices this way? Tell them to join our directory. Hit reply and introduce us—I’d love to connect them with other readers of this newsletter looking for exactly how they think about dentistry.
References
Chambers, E. S., et al. (2015). Effects of targeted delivery of propionate to the human colon on appetite regulation, body weight maintenance and adiposity in overweight adults. Gut, 64(11), 1744–1754. https://doi.org/10.1136/gutjnl-2014-307913
Sanchez-Tapia, M., et al. (2020). The diet–gut microbiota–brain axis and its influence on metabolic and neurodegenerative diseases. Frontiers in Nutrition, 7, 112. https://doi.org/10.3389/fnut.2020.00112
Segata, N., et al. (2012). Composition of the adult digestive tract bacterial microbiome based on seven mouth surfaces, tonsils, throat and stool samples. Genome Biology, 13(6), R42. https://doi.org/10.1186/gb-2012-13-6-r42
Tolhurst, G., et al. (2012). Short-chain fatty acids stimulate glucagon-like peptide-1 secretion via the G-protein–coupled receptor FFAR2. Diabetes, 61(2), 364–371. https://doi.org/10.2337/db11-1019
Low-fat advice didn’t just fail us—it hardened our arteries.