Oral bacteria and systemic disease links

Research has identified potential connections between oral health and various systemic diseases. Studies indicate that periodontitis and specific oral bacteria may contribute to increased risks for different conditions.

In relation to colorectal cancer, researchers have observed oral bacteria within large intestine tumors. A 2025 review noted that Fusobacterium nucleatum was present in approximately 45% of analyzed colorectal tumor tissues, while Porphyromonas gingivalis, associated with gum disease, was found in about 21% of tissues. Scientists are currently working to differentiate the impact of gum disease from other shared risk factors like diet, age, and obesity.

Separately, investigations into neurodegenerative disorders suggest a link between periodontal disease and Alzheimer’s disease. Research published in Science Advances identified Porphyromonas gingivalis in the brains of Alzheimer’s patients, with mouse experiments demonstrating that the bacterium can travel from the mouth to the brain and cause nerve cell damage.