Oral bacteria linked to increased colorectal cancer risk

Research indicates a potential link between periodontitis—chronic inflammation of the gums—and an increased risk of colorectal cancer. Studies have identified oral bacteria within large intestine tumors, suggesting that microbes from the mouth may travel to the gut and disrupt the microbiome balance, potentially causing long-term inflammation.

A 2025 review estimated that the bacterium Fusobacterium nucleatum is present in approximately 45% of analyzed colorectal tumor tissues. Additionally, Porphyromonas gingivalis, which is associated with gum disease, was found in about 21% of these tissues.

While observational studies show an association, researchers are working to distinguish the impact of gum disease from shared risk factors such as smoking, obesity, diet, and age. Previous analyses have shown varying levels of increased risk, including a 44% higher risk in a 2021 study and a 21% higher risk in a 2024 study involving 16.6 million participants.