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Oral Cancer Is No Match for a Healthy Oral Microbiome

Fostering a healthy oral microbiome can fight oral and other cancers. That’s nothing to say for its benefits on cavities, root canal infections, and gum disease. Your friendly bacteria protect you from disease, fight tumors, cool off inflammation, and boost your immune system.

Who wouldn’t want this army of microscopic warriors on their side?!

In this blog, you will learn that cancers can be caused by bacteria, viruses, and fungi. One of the best defenses against oral cancers (and other cancers) is a healthy and strong oral microbiome.

What is Oral Cancer?

You or someone you know may have had oral cancer. Or maybe mouth and throat cancer aren’t really on your radar. However, oral cancers affect many people. In the United States alone, 145 people are diagnosed with oral cancer every day. Each hour someone dies from oral cancer. 🙁

Oral cancer includes:

  • Mouth cancer (including the lips)
  • Tongue cancer
  • Tonsil cancer
  • Throat cancer

Oral cancer symptoms are:

  • A mouth sore that doesn’t heal
  • A lump or growth
  • A white or red patch on the inside of the mouth
  • Loose teeth
  • Mouth pain
  • Ear pain
  • Painful or difficult swallowing

The known causes of oral cancer are tobacco use, heavy drinking, and infection with HPV-16 (human papillomavirus version 16). HPV-16 is a common sexually transmitted virus; the same one that can cause cervical cancer in women. Poor oral hygiene is another top risk factor for oral cancer.

Treatments for oral cancer include surgery and radiation. Occasionally chemotherapy is used to treat oral cancer. Finding it early is the key to a good outcome: 80-90% of people will survive. Unfortunately, most cases are found very late. That leads to a high death rate of 43% in the five years following diagnosis.


An Imbalanced Microbiome Can Cause Cancer

How often do you hear about cancer being caused by a microorganism? Not too often. Yet 15.4% of cancers are believed to be caused by microorganisms.1 And it might be more. Helicobacter pylori, the bacterium that causes ulcers and gastric cancer put microbial causes of cancer back on the map. The link was ever more clear when H. pylori was classified as a carcinogen by the World Health Organization.1 Viruses can cause cancer, such as HPV, mentioned above. And many bacteria have been implicated in cancers.

If microbes can cause cancer, then a strong microbial defense is your best protection. Enter the oral microbiome.

The oral microbiome is made up of all of the microorganisms in your mouth including bacteria, fungi, viruses, and bacteriophages, as well as their genetic material. Most of these organisms do no harm and even protect or benefit your health. A small percentage can harm you.

If your oral microbiome is strong and healthy, then harmful bacteria, viruses, or fungi can’t hurt you. However, if the oral microbiome is weak, then bad microbes can rise to power and take over. They can cause oral dysbiosis and cancer. For example, HPV is necessary to cause certain cancers. However, only 0.3 – 1.3% of HPV infections turn into cancer. The body seems to clear the other 98%. Scientists believe that a healthy microbiome may prevent HPV from causing cancer, while an unhealthy microbiome might make it worse.2

When we talk about an unhealthy microbiome, we often use the word, “dysbiosis.” Oral dysbiosis is a mouth that is unhealthy because the microorganisms are out of balance. An imbalanced microbiome may lead to symptoms or disease.

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Symptoms of Oral Dysbiosis:

  • Bad breath
  • Bleeding, puffy, swollen gums
  • Cavities
  • Gingivitis
  • A history of “bad teeth” or lots of dental work
  • Periodontal disease
  • Root canal infections
  • Teeth that are loose or fall out


One of the most common ways we keep a balanced oral microbiome is with oral hygiene. Brushing, flossing, water flossing, dental health check-ups, and oil pulling promote a healthier oral microbiome. When oral care habits fall to the wayside, that’s when oral cancers rear their ugly heads.3 And that’s not all. Poor dental health habits increase the risk for other cancers, too.

Oral Health Habits Can Make or Break Cancer

  • Good dental hygiene reduces the risk of oral cancer by 62%.
  • People who have lost teeth (a sign of gum disease and oral dysbiosis) have an increased risk of gastric cancer and pancreatic cancer.
  • People with gum disease have four times higher risk of head and neck cancer and five times higher risk of tongue cancer!
  • People who don’t brush have two times higher risk of esophageal cancer.

Why? It’s because a healthy oral microbiome protects you from infections. If you have gum disease, then you have imbalanced bacteria in your mouth causing destruction and inflammation. This harmful environment gives more chances for cells to become damaged and turn into cancer. Fewer infections and less inflammation in your mouth means you are safer from developing cancer.


Beyond Mouth and Throat Cancers

It’s clear that certain oral pathogens are involved in mouth and throat tumors.1,4,5 But the oral microbiome may influence cancers elsewhere too, not just oral cancers! Oral pathogens increase the risk of colorectal cancer and may help to predict gastrointestinal cancer.6 Also, there is more oral dysbiosis in people who have esophageal, gastric, pancreatic, and colorectal cancers.


Oral microorganisms can cause not only head and neck cancers but cancers throughout the whole human body. (Sun et. al., 2020)



How Does Oral Dysbiosis Lead to Cancers?

It’s well accepted that oral dysbiosis and infections can set someone up for cancer.1,4,6-12 But just how do imbalanced bacteria cause mouth cancers? Here are the different ways an imbalanced oral microbiome could lead to cancer.8,11

Inflammation– if someone has oral dysbiosis such as cavities or gum disease, they have inflammation in the mouth. These immune products can harm healthy cells and cause them to mutate into unhealthy cancer cells.

Harmful bacterial byproducts– microorganisms can produce cancer-causing toxic byproducts, including free radicals that can damage your cells and turn them rogue.

Antiapoptotic activity– some microbes may suppress the body’s self-defense mechanism of programmed cell death, known as apoptosis. This means harmful mutated cells can live forever and cause cancer when they shouldn’t be allowed to.

Immune suppression– some microbes lower your immune defenses so that your immune system can’t fight dysbiosis or cancer cells.

Damage to the oral lining (leaky mouth)- having oral dysbiosis and inflammation in the mouth can produce chemicals that damage the lining of the mouth. That means harmful chemicals, proteins, and microorganisms can enter the bloodstream, where they don’t belong.

Epigenetic changes to host cells– some evidence suggests that microbes can influence our DNA, possibly producing tumors. Epigenetics describes the changes to how our DNA acts that often come from environmental causes and can be passed down. These changes are overlaid on our genes; they are not changes to our actual raw DNA code.

Decreased production of anticancer metabolites by friendly bacteria4– one reason bad bacteria may cause cancer is they push out all of the good bacteria that actually fight cancer with their healthy byproducts.


Boost Your Oral Microbiome with These Natural Oral Health Solutions

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  • Get all of the information you need in my book, Heal Your Oral Microbiome.
  • Brush, floss, and stay on top of your dental health visits.
  • Get screened; some dental offices do free screening in April for Oral Cancer Awareness.
  • Eat whole foods, especially colorful veggies.
  • Just say no to sugar and refined carbohydrates.
  • Take chewable probiotics containing Streptococcus salivarius. I also recommend oral probiotics, which have good evidence to support prevention of colorectal cancer. However, evidence for anticancer effects in the mouth are limited.
  • Test your mouth and your gut microbiomes to look for dysbiosis.
  • Stop smoking.
  • Stop drinking (too much) alcohol.
  • Choose organic foods and non-toxic dental products to reduce cancer-promoting chemicals in the mouth.


Your oral health is now more important than ever. From diabetes to heart disease to Alzheimer’s, the list of diseases linked to your oral health grows longer and longer. Imbalanced microorganisms in the mouth can cause cancers of the mouth, throat, esophagus, stomach, pancreas, and even the colon. A healthy and strong oral microbiome may be your best weapon against oral cancer and other cancers.


  1. Zhao H, Chu M, Huang Z, et al. Variations in oral microbiota associated with oral cancer. Scientific reports. 2017;7(1):11773.
  2. Vyshenska D, Lam KC, Shulzhenko N, Morgun A. Interplay between viruses and bacterial microbiota in cancer development. Semin Immunol. 2017;32:14-24.
  3. Meurman JH. Oral microbiota and cancer. Journal of oral microbiology. 2010;2.
  4. Su SC, Chang LC, Huang HD, et al. Oral microbial dysbiosis and its performance in predicting oral cancer. Carcinogenesis. 2021;42(1):127-135.
  5. Mäkinen A, Nawaz A, Mäkitie A, Meurman JH. Role of Non-Albicans Candida and Candida Albicans in Oral Squamous Cell Cancer Patients. Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons. 2018;76(12):2564-2571.
  6. Zhang S, Kong C, Yang Y, et al. Human oral microbiome dysbiosis as a novel non-invasive biomarker in detection of colorectal cancer. Theranostics. 2020;10(25):11595-11606.
  7. Mascitti M, Togni L, Troiano G, et al. Beyond Head and Neck Cancer: The Relationship Between Oral Microbiota and Tumour Development in Distant Organs. Frontiers in cellular and infection microbiology. 2019;9:232.
  8. Sun J, Tang Q, Yu S, et al. Role of the oral microbiota in cancer evolution and progression. Cancer medicine. 2020;9(17):6306-6321.
  9. Hong BY, Sobue T, Choquette L, et al. Chemotherapy-induced oral mucositis is associated with detrimental bacterial dysbiosis. Microbiome. 2019;7(1):66.
  10. Koliarakis I, Messaritakis I, Nikolouzakis TK, Hamilos G, Souglakos J, Tsiaoussis J. Oral Bacteria and Intestinal Dysbiosis in Colorectal Cancer. International journal of molecular sciences. 2019;20(17).
  11. La Rosa GRM, Gattuso G, Pedullà E, Rapisarda E, Nicolosi D, Salmeri M. Association of oral dysbiosis with oral cancer development. Oncology letters. 2020;19(4):3045-3058.
  12. Mohammed H, Varoni EM, Cochis A, et al. Oral Dysbiosis in Pancreatic Cancer and Liver Cirrhosis: A Review of the Literature. Biomedicines. 2018;6(4).


Cass Nelson-Dooley, M.S.

Cass Nelson-Dooley, M.S.

Cass Nelson-Dooley, MS, is a researcher, author, educator, and laboratory consultant. She studied medicinal plants in the rain forests of Panama as a Fulbright Scholar and then launched a career in science and natural medicine. Early on, she studied ethnobotany, ethnopharmacology, and drug discovery at the University of Georgia and AptoTec, Inc. She joined innovators at Metametrix Clinical Laboratory as a medical education consultant helping clinicians use integrative and functional laboratory results in clinical practice. She owns Health First Consulting, LLC, a medical communications company with the mission to improve human health using the written word. Ms. Nelson-Dooley is an oral microbiome expert and author of Heal Your Oral Microbiome. She was a contributing author in Laboratory Evaluations for Integrative and Functional Medicine and Case Studies in Integrative and Functional Medicine. She has published case studies, book chapters, and journal articles about the oral microbiome, natural medicine, nutrition, laboratory testing, obesity, and osteoporosis.