Bacteria in Your Mouth and Cancer

By Richard Asa and Temma Ehrenfeld @temmaehrenfeld
October 13, 2023
Bacteria in Your Mouth and Cancer

The condition of your mouth can affect your entire body — even your risk of cancer. Here’s how to protect your gums from bacteria buildup and the associated risks.

Brush. Floss. Rinse your mouth with an antibacterial solution. Chew sugarless gum. Do so daily.

It may be a bore, but good oral hygiene doesn’t just save you the pain and expense of cavities, bleeding gums, and lost teeth.

It is the first line of defense against gum disease, or periodontitis, which is linked to several other diseases, including cancer. The evidence goes back for decades.

If you tend to ignore your mouth and skip brushing, it might motivate you to know that a growing body of research suggests gum disease raises your risk of cancer from 13 to 45 percent.


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Gum disease and cancer

The cancer risk has been documented in surveys of large populations over time. For example, one study used data from nearly 66,000 older U.S. women, who were tracked for eight years, on average. The women who said they’d had gum disease had a 14 percent higher risk of developing any kind of cancer during that time.

After your gut, your mouth and throat contain the largest and most diverse ecosystem of microorganisms, called a microbiome, of any part of your body. It includes some 700 species of bacteria, plus fungi, viruses, and protozoa.

Gum disease arises as a byproduct of particular strains of bacteria. You can’t keep them out of your mouth, but you can brush, floss, and rinse them away.

One possible explanation for a link to cancer is that dangerous bacteria travel from your mouth through your blood. Chronic inflammation, a heightened immune response tied to many diseases, especially as you age, may also increase your risk of cancer.

Cancers close to your mouth are most strongly linked to gum disease. In the study mentioned earlier, gum disease tripled the chances of cancer of the esophagus.

Smoking also makes things worse. The women who reported both smoking and gum disease had higher rates of breast, lung, and gallbladder cancer. People with gum disease, but who never smoked, had a higher chance of melanoma.

Gum disease is a problem for males who don’t smoke, too, according to a study of male health professionals, which found an increased risk of 13 percent for any kind of cancer.

The more extreme the gum disease, the greater the risk of cancer, which jumps 25 percent or more depending on severity. Losing teeth is an especially bad sign. In the male health professionals study, the increased risk of cancer was 45 percent among men who said they had fewer than 17 of their teeth.

But those reports may be underestimates. When researchers look at dental records, they tend to find that volunteers don’t always report gum disease or tooth loss, which suggests that the link with cancer might be even higher.

Other research has explored links between gum disease and particular cancers, including cancer of the kidney, pancreas, blood, stomach, liver, and colon.

Periodontitis is also an independent risk factor for heart disease, type 2 diabetes, chronic obstructive pulmonary disease (or COPD), obstructive sleep apnea, and COVID-19 complications.

What you can do

Your best move is to prevent gum disease, which begins when plaque builds up along and under your gum line. Plaque is a thin, sticky substance, a kind of biofilm, made of many layers of hundreds of different kinds of bacteria. The bacteria constantly reproduce and accumulate unless you clean your teeth. A buildup of plaque tends to make your teeth feel fuzzy or grimy. 

If you don’t get rid of plaque, it hardens into tartar that a dental hygienist needs to remove.

If your gums are red, tender, and prone to bleeding, a condition called gingivitis, you’re not cleaning your teeth well enough.

When your gums are in more trouble, you’ll see gobs of blood in your mouth. You may have pain chewing or lose teeth. You’ll need attention from a special kind of dentist.

To prevent gum disease:

  • Brush your teeth twice a day with fluoride toothpaste.
  • Floss regularly.
  • Visit your dentist routinely for a checkup and cleaning. Tell the dentist about any medical conditions you have and medications you take.
  • Eat a well-balanced diet. Avoid candies, syrup, and sweetened soda.
  • Quit smoking. Smoking increases your risk of gum disease.
  • Consider chewing sugarless gum, especially after meals, to help increase the flow of saliva, which can minimize plaque and wash out food from your teeth.
  • Use an antiseptic mouthwash daily to kill germs that lead to gum disease. In a small clinical trial, a mouthwash with the four essential oils in Listerine —eucalyptus, mint, wintergreen, and thyme — significantly reduced plaque, gingivitis, and bleeding after 12 weeks of twice-daily rinsing.  


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October 13, 2023

Reviewed By:  

Christopher Nystuen, MD, MBA and Janet O'Dell, RN