Scientists say that failing to brush your teeth regularly could triple your risk of developing pancreatic cancer, after their study discovered discovered that harmful bugs originating from the mouth can be carried through the saliva into the pancreas, ramping up the risk of this particular cancer.
The Independent reports that poor oral hygiene has long been linked to various diseases, but there is now a better understanding of why.
It has always been known that the presence of harmful bacteria and fungi in the mouth leaves people more vulnerable to diseases – like cancer – than those with healthier mouths, but this latest study, led by a team from NYU School of Medicine, specifies just which bacteria and fungi cause the increase in risk.
“It is clearer than ever that brushing and flossing your teeth may not only help prevent periodontal disease but may also protect against cancer,” co-author and population health expert Dr Richard Hayes wrote in JAMA Oncology.
The study tested 122 000 people and identified three different oral periodontal pathogens, 20 additional bacteria and four fungi. Over eight years, the team assessed which bacteria and fungi led to increased incidences of one of the deadliest forms of cancer.
They used data from two investigations tracking participants in America for around eight years. These were the American Cancer Society Cancer Prevention Study-II Nutrition Cohort and the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial.
Candidates provided oral samples after rinsing with mouthwash, and those who were prospectively diagnosed with pancreatic cancer were identified during a follow-up.
Of the 122 000 participants, 445 developed pancreatic cancer and were matched with 445 “controls” – participants who remained cancer-free. Of the 890 participants, the average age was 67 and 53.3% were male, with the rest female.
“Oral bacterial periodontal pathogens – P gingivalis, E nodatum, and P micra – were associated with increased risk of pancreatic cancer,” the authors wrote in their conclusion.
“A bacteriome-wide scan revealed eight oral bacteria associated with decreased and 13 oral bacteria associated with increased risk of pancreatic cancer.”
One fungi, known as candida, was singled out as being particularly associated with pancreatic cancer.
As a result, the authors said, oral bacteria and fungi were significant risk factors for pancreatic cancer development.
The findings could allow oncologists in future to identify people at high risk of developing this cancer, allowing healthcare providers to develop a more personalised prevention plan.
Pancreatic cancer has one of the lowest survival rates of any form of cancer, largely because it is often diagnosed too late, due to very vague symptoms.
Study details
Oral Bacterial and Fungal Microbiome and Subsequent Risk for Pancreatic Cancer
Yixuan Meng, Feng Wu, Soyoung Kwak, Richard Hayes et al.
Published in JAMA Oncology on 18 September 2025
Abstract
Importance
The oral microbiota may be involved in the development of pancreatic cancer, yet current evidence is largely limited to bacterial 16S amplicon sequencing and small retrospective case-control studies.
Objective
To test whether the oral bacterial and fungal microbiome is associated with the subsequent development of pancreatic cancer.
Design, Setting, and Participants
This cohort study used data from two epidemiological cohorts: the American Cancer Society Cancer Prevention Study-II Nutrition Cohort and the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Among cohort participants who provided oral samples, those who prospectively developed pancreatic cancer were identified during follow-up. Control participants who remained free of cancer were selected by 1:1 frequency matching on cohort, 5-year age band, sex, race and ethnicity, and time since oral sample collection. Data were collected from August 2023 to September 2024, and data were analysed from August 2023 to January 2025.
Exposures
The oral bacterial and fungal microbiome were characterised via whole-genome shotgun sequencing and internal transcribed spacer (ITS) sequencing, respectively. The association of periodontal pathogens of the red complex (Treponema denticola, Porphyromonas gingivalis, and Tannerella forsythia) and orange complex (Fusobacterium nucleatum, F periodonticum, Prevotella intermedia, P nigrescens, Parvimonas micra, Eubacterium nodatum, Campylobacter shower, and C gracilis) with pancreatic cancer was tested via logistic regression. The association of the microbiome-wide bacterial and fungal taxa with pancreatic cancer was assessed by Analysis of Compositions of Microbiomes With Bias Correction 2 (ANCOM-BC2). Microbial risk scores (MRS) for pancreatic cancer were calculated from the risk-associated bacterial and fungal species.
Main Outcomes and Measures
Pancreatic cancer incidence.
Results
Of 122 000 cohort participants who provided samples, 445 developed pancreatic cancer over a median (IQR) follow-up of 8.8 (4.9-13.4) years and were matched with 445 controls. Of these 890 participants, 474 (53.3%) were male, and the mean (SD) age was 67.2 (7.5) years. Three oral bacterial periodontal pathogens—P gingivalis, E nodatum, and P micra—were associated with increased risk of pancreatic cancer. A bacteriome-wide scan revealed 8 oral bacteria associated with decreased and 13 oral bacteria associated with increased risk of pancreatic cancer (false discovery rate–adjusted Q statistic less than .05). Of the fungi, genus Candida was associated with increased risk of pancreatic cancer. The MRS, based on 27 oral species, was associated with an increase in pancreatic cancer risk (multivariate odds ratio per 1-SD increase in MRS, 3.44; 95% CI, 2.63-4.51).
Conclusions and Relevance
In this cohort study, oral bacteria and fungi were significant risk factors for pancreatic cancer development. Oral microbiota hold promise as biomarkers to identify individuals at high risk of pancreatic cancer, potentially contributing to personalised prevention.
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