Your saliva could contain clues to hidden signs of disease, according to new research that found microbes in the mouth may reveal patterns linked to two forms of cancer. Scientists say the findings could eventually pave the way for a simpler, less invasive screening test that starts with a quick mouth rinse rather than a traditional stool sample. The study, published in Cell Host & Microbe, examined the relationship between bacteria found in the mouth and those present in the digestive system.
Scientists found that patterns in these microbial communities appeared to differ by a person's health status, raising the possibility that oral samples could one day be used for disease screening. The researchers said the strongest signals were linked to gastric (stomach) cancer and colorectal cancer, two of the most common gastrointestinal cancers worldwide. The American Cancer Society estimates there will be about 31,510 new stomach cancer cases and 108,860 new colon cancer cases in 2026.
"Many species of microbes associated with the mouth are also present in the gut and may flourish there," lead author Jihyun F. Kim of Yonsei University in Seoul said in a statement. "These observations made us wonder whether oral microbes reach and persist in the gastrointestinal tract differently in people with cancer." This media contains content some readers may find distressing or offensive.
Viewer discretion is advised. To investigate, researchers recruited 507 volunteers who provided both oral and fecal samples. The study group included 129 healthy individuals, 215 people with metabolic disorders such as metabolic syndrome, hypertension, hyperlipidemia and type 2 diabetes, 77 people with gastric cancer and 86 people with colorectal cancer.
Researchers collected samples from cancer patients before any treatment began. Using gene sequencing, the team created what they called a "mouth-to-feces" (MF) index. The tool measures how many identical microbial variants are shared between a person's mouth and gut.
Researchers then assessed whether the MF index could distinguish people with cancer from healthy participants. The analysis revealed clear microbial signatures in participants with gastric and colorectal cancer. Patients with either form of cancer showed significantly higher MF index scores than healthy individuals.
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