“It is clearer than ever that brushing and flossing your teeth may not only help prevent periodontal disease but may also protect against cancer,” Dr. Richard Hayes of NYU Grossman School of Medicine said. That statement now carries new weight after the largest study to date revealed that harmful bacteria and fungi in the mouth could raise the risk of pancreatic cancer more than threefold.
Researchers analyzed saliva DNA from 122,000 participants in two large US health cohorts over a period of almost nine years. Of these, 445 developed pancreatic cancer, and each was matched with a cancer-free control. The team identified 27 microbial species 23 bacteria and 4 fungi that were significantly associated with pancreatic cancer risk. Of these, three well-known periodontal pathogens stood out: Porphyromonas gingivalis, Eubacterium nodatum, and Parvimonas micra.
The results, published in JAMA Oncology, were the first to implicate oral fungi, specifically yeast from the genus Candida, in pancreatic cancer. Species such as Candida tropicalis and unspecified Candida strains were associated with a 34–43% higher risk. That adds to previous research demonstrating that bacteria can make their way from the mouth to the pancreas via swallowed saliva and create inflammation or other cellular changes that promote cancer.
Based on the oral microbiome of each participant, scientists calculated a microbial risk score that could predict cancer risk individually. A one-standard-deviation increase in this score was associated with more than a threefold increase in pancreatic cancer risk. “By profiling bacterial and fungal populations in the mouth, oncologists may be able to flag those most in need of pancreatic cancer screening,” said Professor Jiyoung Ahn, co-senior author of the study.
The connection between oral health and pancreatic cancer has been long suspected. Previous studies have associated Porphyromonas gingivalis with a 59% higher risk for the disease, probably by way of chronic gum infections and systemic inflammation. Periodontitis a serious gum disease that affects up to 90% of older adults has also been linked to poor prognosis in cancer, likely because of how pathogenic bacteria interfere with normal immune responses, damage tissues, and affect normal cell cycles.
The consequences reach far beyond the mouth: Periodontal pathogens promote gut microbiota shifts, increase oxidative stress, and even interfere with tumour-suppressor genes such as p53. These changes establish an environment in which the pancreatic cells will be more susceptible to mutations and uncontrolled growth. In laboratory models, P. gingivalis has been shown to survive inside pancreatic tumour cells, enhancing their proliferation and modifying the tumour microenvironment.
While smoking, obesity, and specific genetic syndromes remain established risk factors, they explain less than 30% of pancreatic cancer cases. This makes the oral microbiome a promising frontier for prevention and early detection. Non-invasive saliva profiling can be used to complement prevailing strategies in screening high-risk populations, such as those with strong family histories or inherited mutations.
Experts caution that these findings show correlation, not causation, and more research is needed before oral microbiome testing becomes a routine screening tool. Still, the message for everyday health is clear: good oral hygiene-through regular brushing, flossing, and dental check-ups-may help lower systemic disease risks, including some cancers. Lifestyle habits that support a balanced oral microbiome, such as quitting smoking and moderating alcohol intake, could also play a protective role.
Pancreatic cancer is one of the most lethal malignancies, since symptoms such as jaundice, unexplained weight loss, and changes in bowel movements can be so insidious. Survival prospects dramatically improve with earlier detection. It’s hoped that one day, advances in microbiome science could allow clinicians to identify risk long before symptoms occur, allowing for a crucial window of intervention.
