Want to avoid cancer? Consider brushing and flossing more often.

Why? Folks with bad gums might be at higher risk of developing certain types of cancer, new research suggests.

A history of gum disease appears to increase the risk of stomach cancer by 52% and throat cancer by 43%, according to data from two major long-term health studies.

People who'd lost two or more teeth also had an increased risk of cancer—33% for stomach cancer and 42% for throat cancer—compared with people who never lost a tooth, the researchers reported.

"Participants with periodontal disease and a higher number of teeth lost had a higher risk of developing the two gastrointestinal cancers, even after adjusting for other major risk factors," said senior researcher Mingyang Song. He's an assistant professor of clinical epidemiology and nutrition at the Harvard T.H. Chan School of Public Health in Boston.

If these findings pan out, then a great many people in the United States could be at increased risk for these cancers. Nearly half of adults aged 30 and older have gum disease, according to the U.S. Centers for Disease Control and Prevention.

For the study, the researchers analyzed health data gathered from tens of thousands of health professionals during two long-term studies—including over 98,000 women in the Nurses' Health Study and over 49,000 men in the Health Professionals Follow-Up Study.

During 22 to 28 years of follow-up, participants developed 199 cases of throat cancer and 238 cases of stomach cancer.

Overall, people with any history of gum disease had a 59% increased risk of throat cancer compared with people who'd never had periodontal disease, regardless of whether they'd lost teeth or not, the findings showed.

There was some difference when looking at stomach cancer. People with gum disease who lost no teeth had a 50% increased risk of stomach cancer, while those who'd lost one or more teeth had a 68% increased risk.

Peter Campbell is scientific director of epidemiology research for the American Cancer Society. He said, "The mouth, esophagus and stomach are all connected, of course, and they're important components of the digestive system. It's not surprising to see that a marker for illness of one organ is connected to another illness, such as cancer, further down the [gastrointestinal] tract."

Song said that the inflammation caused by gum disease might be one factor that increases cancer risk.

"People with periodontal disease tend to have higher systemic inflammation, which is one of the underlying mechanisms of cancer development," he explained.

It's also possible that bad oral health promotes the growth of bacteria in the mouth and gums that could contribute to cancer, Song and Campbell noted.

"From this study, and others like it," Campbell said, "it seems that some of the same bacteria and related pathogens that lead to tooth loss and gum disease are also associated with tumors in the stomach and esophagus."

The cancer risk related to gum disease in this study was independent of tobacco use, which means that smokers with poor oral health might face an even higher risk of these gastrointestinal cancers, Song added.

And it's possible that the longer you have bad gums, the more likely your cancer risk will increase, Song and Campbell suggested.

"It certainly seems plausible that having a longer duration of periodontal disease would be associated with even higher risks of these cancers," Campbell said. "Some of that association may be explained by simply being older, which in itself is a strong risk factor, but we tend to account for that issue pretty well."

If you have a history of bad gums and want to reduce your potential cancer risk, Campbell recommends seeing a dentist regularly, taking good care of your oral health, learning the signs and symptoms of cancer, and undergoing all age-appropriate cancer screenings.

Song and Campbell both also called for more study into this possible cancer risk, including clinical trials.

The new study was published July 20 in the journal Gut.

—Dennis Thompson, Healthday Reporter