Oral bacteria and colorectal cancer: The connection we rarely talk about

It’s a conversation that sits just outside the usual scope of oral-systemic care—and one that raises questions about what clinicians may be overlooking.

Episode description

Dental conversations around oral-systemic health often center on familiar territory—cardiovascular disease, diabetes, and head and neck cancers. In this episode of Fast Facts: Ask the Expert, Machelle Hudson shifts that focus to a connection that is less frequently discussed: the potential role of oral bacteria in colorectal cancer.

The discussion revisits what clinicians already understand about periodontal pathogens—their ability to influence intracellular pathways, promote cell survival, and contribute to processes like migration and invasion. While these mechanisms are commonly associated with head and neck cancers, their implications may extend further than many dental professionals routinely consider.

Hudson highlights research identifying identical strains of bacteria, including Fusobacterium nucleatum, in both oral and colorectal samples of patients with colorectal cancer. The presence of these pathogens across sites—particularly in patients with periodontal disease—raises important questions about how oral health may intersect with systemic disease risk.

As screening improves and awareness grows, the conversation turns to the role of dentistry in prevention. From pathogen testing to patient communication, the episode underscores a broader responsibility: recognizing where oral findings may signal something more.

Key takeaways

• Colorectal cancer is one of the most common cancers, yet its connection to oral pathogens is not routinely addressed in dental conversations.
• Periodontal bacteria are known to influence cellular pathways tied to cancer development, including survival, migration, and invasion.
• Research has identified identical strains of Fusobacterium nucleatum in both oral and colorectal samples of affected patients.
• Patients with periodontal disease may carry these pathogens in both the mouth and gut, suggesting a possible systemic pathway.
• Salivary diagnostics and pathogen testing can provide additional context for risk assessment, particularly in patients with relevant family history.

Editor's note: This episode was originally published March 14, 2024, and this page was updated with new information about the episode on April 8, 2026.

Full episode transcript

Andrew Johnston

You're listening to Fast Facts: Ask the Expert with Machelle Hudson Hoover.

Welcome back, everyone, into Fast Facts: Ask the Expert, Oral Systemic Edition with Machelle Hudson Hoover. Welcome back, Machelle.

Machelle Hudson

Hello, how are you doing?

Andrew Johnston

I'm doing good. It's February. I have a very specific question for you today.

Are you ready for this one?

Machelle Hudson

I am.

Andrew Johnston

All right. So we talk a lot about oral bacteria and how that can play a role in diseases throughout the body, right?

So the very specific question for you is, how does that same oral bacteria impact colorectal cancer risk?

Machelle Hudson

Why this matters more than we talk about

Oh, this is good, Andrew. How often do we talk about this? How often do you hear about it? You don't.

Andrew Johnston

Honestly, almost never, yeah.

Machelle Hudson

This is really another encouragement and really instilling value in the importance of we dental professionals.

So what do we know about periodontal pathogens when it comes to head and neck cancers that we're very comfortable talking about, right? We know that they affect specific intracellular pathways and promote cell survival.

I mean, I know this is a little bit sciency, but we know that, you know, they can activate these pathways and reduce protein expression and increase cell migration and invasion. And I know that's scary.

So we're used to hearing that, again, with head and neck cancers. But what we don't talk about is colorectal cancer, and it's actually a really big deal.

Colorectal cancer prevalence and screening

So a little bit—we know that excluding skin cancers, colorectal cancer is the third most common cancer diagnosed in both men and women, y'all.

And now we've gotten better at screening. And so I am grateful that we are really proactive in that.

I'm not sure about you, Andrew, but I do get screened. I don't have to get screened, but the last one I went to a couple of years ago, I get another, you know, seven years before another one that I need.

So we know that we're losing over a hundred thousand to colorectal cancer a year, and that's actually more than stroke. So that should raise a real big red flag with everyone and how we need to get awareness out when it comes to this very heartbreaking disease.

And so we know that new cases of colon cancer: 106,000; rectal cancers: 46,000. So that's one in 23 men and then one in 26 women.

Oral-systemic connection and bacteria

So what do we know about the oral and systemic connection when it comes to this? Well, it all comes down to bacteria.

And I'm a big believer in pathogen testing. And really, I speak pathogen testing because our goal is to understand our patients' oral risk, and what we get to complement by understanding specific bacteria is systemic risk as well.

And so we know that dentistry's responsibility in playing a role in prevention and treatment is significant.

So gut microbiota plays an important role in the bacteria when it comes to colorectal cancer, and specific bacteria are going to be, you know, like FN, we're used to hearing about, PG, Porphyromonas gingivalis, that I know Katrina Sanders talks a lot about on her podcast, and many more.

What the research shows

But we know that in one study, they isolated and cultured identical strains of F. nucleatum in the saliva and fecal species of patients that had colorectal cancer.

And what they found is that in healthy people—they also looked at cultures from healthy—sorry. And what they found is that they had no F. nucleatum.

And that should be really concerning.

But in patients with periodontal disease, they found them at both locations. And that just—I don't know about you, Andrew—but that actually just gave me the shivers because that is—what does that do?

Responsibility, right? And I'm really responsibility-focused.

And it's an uncomfortable conversation to have, but it's a necessary conversation to have in treatment and disease.

Andrew Johnston

So what it sounds like, though, is getting tested and having the diagnostics are really important in helping us understand if we are at risk, is what it sounds like.

Machelle Hudson

I think it's incredibly important to screen our patients, and we should be confident when we have periodontal pathogen salivary diagnostics on our treatment plan, and also offering that option for our patients that know that they have a family history of colorectal cancer, because we do play a role in prevention.

And there's so much more about this, Andrew, that we don't have time to talk about in a short period.

Andrew Johnston

Yeah, I know. But I appreciate your time today. Thank you so much.

If people want to reach out to you, how can they find you?

Machelle Hudson

Machelle at RDH Health, or you can find us on our website at integrativedentalcoaching.com.

Andrew Johnston

Awesome. Thank you.

Machelle Hudson

Thank you.

Andrew Johnston

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