Esophageal Cancer: Gum Disease Bacteria May Increase Risk by 21 Percent

A young woman brushing her teeth in her bathroom. Three Lions/Getty Images

Is the toothbrush a powerful disease-fighting tool? Maybe. Changes in the collection of bacteria living in our mouths have been linked to colorectal cancer, oral cancer and even diabetes. Bad oral health has also been linked to heart disease, though that might just be because the risk factors for heart disease and gum disease are similar. Bacteria may also alter people's risk of developing esophageal cancer, according to findings published in Cancer Research on Friday.

Researchers took samples of the bacteria found in more than 120,000 people's mouths and ran a DNA analysis to identify all the species that were there. Then, over a 10-year period, they waited to see if anyone would get esophageal cancer; 106 people eventually did.

A few types of bacteria seemed to be more strongly linked with higher or lower risks of esophageal cancer, the authors found. People who had higher levels of Tannerella forsythia and Porphyromonas gingivalis had a higher risk of cancer. Specifically, Tannerella was linked with a 21 percent increased risk; other researchers had previously found high levels of Porphyromonas in esophageal tumors.

One group of bacteria, Neisseria, as well as a species of strep bacteria, were found in people who had a lower risk of cancer.

Water pours onto a toothbrush with toothpaste on January 10, 2007, in Schwelm, Germany. Christof Koepsel/Getty Images

Only 1 percent of all the cancers diagnosed each year in the United States are in the esophagus, but the outlook for those people is generally grim. Less than one in five people live longer than five years after they are diagnosed, according to the National Institutes of Health's cancer-tracking program.

Among other things, smoking, drinking and having bad acid reflux have been linked to a higher risk of getting esophageal cancer, according to the American Cancer Society.

Though the findings are interesting, this study doesn't show that the bacteria caused the cancer, nor can it determine if the increased risk of cancer was associated with the bacteria themselves or the gum disease they can cause. But the bacteria associated with a higher risk of cancer have also been linked to gum disease. (And, as your dentist would say if you confessed to being a casual flosser, a good oral hygiene routine has been linked with a decreased risk of gum disease.)

More research may clarify the links. "Our study indicates that learning more about the role of oral microbiota may potentially lead to strategies to prevent esophageal cancer, or at least to identify it at earlier stages," New York University population health researcher Jiyoung Ahn said in a press release that accompanied the paper. "The next step is to verify whether these bacteria could be used as predictive biomarkers"—that is, whether high levels of these bacteria might be able to serve as a warning sign of esophageal cancer.

Regardless, Ahn said, regular tooth brushing and dental checkups couldn't hurt.