Recent headlines highlight a worrying trend: colorectal cancer is appearing in people at younger ages. That’s understandably alarming.
In this article I examine a developing area of research: the relationship between Fusobacterium nucleatum (Fn) and colorectal cancer (CRC). Specifically, how might the bacteria in your mouth influence colorectal cancer risk?
For nearly a decade, researchers have detected Fn in colorectal tumors and observed links between its presence and poorer clinical outcomes. More recent studies, however, show the relationship is complex: not all Fn strains behave the same way.
Fn is a common member of the oral microbiome and is found in most people’s mouths. It plays a dual role: while it is part of a healthy oral ecology for many, certain Fn strains are associated with gum disease and broader systemic effects. The key to these differing roles lies in genetics—Fn comprises several distinct subspecies and strains, each with different impacts on human health.
A recent study led by Zepeda-Rivera and colleagues at the Fred Hutchinson Cancer Center identified a particular subspecies, Fusobacterium nucleatum animalis, as potentially important in CRC. Within this group, a variant labeled FnaC2 appears enriched in tumor samples and may encourage tumor progression.
The team validated their observations through multiple approaches: genomic analysis of bacterial samples, experiments in animal models, and examination of human tissue. Across these methods, the data consistently pointed to a link between the FnaC2 variant of Fn animalis and colorectal tumors.
What does this mean for you?
These findings are informative but should be interpreted with care. Only certain Fn strains seem implicated in CRC; many strains are benign or even beneficial for oral health. Trying to eliminate Fn entirely from the mouth is neither practical nor advisable.
A more sensible approach is to support balanced oral and gut ecosystems. Good oral hygiene, regular flossing, a nutritious diet, and strategies that reduce chronic inflammation all help maintain a healthy microbiome. Some people also consider targeted oral probiotics under professional guidance. Rather than aiming to remove Fn broadly, focus on practices that reduce gum disease and bleeding and promote overall microbial balance.
Staying informed about your oral microbiome can also be useful. Testing can reveal the composition of oral bacteria and help guide personalized choices to support oral and digestive health.
In other updates from the Ask the Dentist podcast:
In Episode #116 we discuss water purity—an important topic for anyone deciding what kind of filtration to use at home. The episode covers microplastics, fluoride, and common misconceptions like the idea that distilled water is “too pure.” It’s a practical conversation for families and individuals concerned about their water quality.
Thank you for reading this installment of Mondays with Mark. If you listen to the podcast, please consider leaving a review on your preferred platform; each review is read and appreciated.
P.S. As a daily tea drinker, I care about purity and safety. That’s why I choose teas that undergo rigorous toxin screening and quality testing to ensure both cleanliness and bioactivity—so my tea supports oral health as well as taste.