Despite the mouth and gut being on opposite ends of the gastrointestinal tract, researchers have studied the relationship between oral and intestinal health for quite some time now. The GI tract serves as a pathway for bacteria and pathogens to travel from the mouth to the intestines, making oral health a potential driver of downstream gastrointestinal and systemic health effects.
Lines of Defense
In disease prevention, the oral-intestinal relationship begins at the mouth. Various lines of defense exist to prevent harmful bacteria from reaching and harming the stomach. The first line of defense, saliva, contains many enzymes and antimicrobial peptides that break down bacteria’s protective walls. Oral tissue, similarly, protects the body from pathogens by blocking their ability to enter the bloodstream. Any pathogens tricky enough to evade these initial defenses and enter the bloodstream are often destroyed by circulating immune cells.
The gastrointestinal system deploys various chemical and mechanical defenses against foreign pathogens as well. Chemically, the system’s highly acidic pH makes it difficult for microorganisms to survive. Additionally, the intestine lining contains junction proteins that connect epithelial cells which regulate nutrient extraction and eliminate harmful waste. The liver–which functions in tandem with the GI system to filter toxins–uses bile salts as signals for immune cells to mark and destroy pathogens. Finally, in the stomach, pepsin functions as a digestive enzyme that breaks down proteins, including those composing bacterial bodies.
Bacterial Translocation
If any of these defenses are weakened, orally-ingested pathogens can manifest into disease. Bacterial translocation, or travel, from the mouth to other internal structures like the GI tract is what gives bacteria enough power to harm the human body. Translocation most readily occurs with decreased saliva production, elevated stomach pH, or antibiotic usage which fosters oral bacteria colonization in the gut.
Pathogens primarily travel from the mouth to the gut when saliva, food, and beverages are swallowed–a pathway known as the oral-gut microbiome axis. Most swallowed bacteria that migrate to the gastrointestinal microbiome are acid-resistant, meaning they are able to withstand the harsh chemical environments of the stomach and intestines. One example of such bacteria is Porphyromonas gingivalis, the species most closely associated with gum disease. A study aimed to discover the connections of oral diseases with gut health found that P. gingivalis were able to translocate from the mouth to the colon, inhibiting proper function and fostering higher levels of toxins (which implicate associated cancers).
It is important to mention that bacterial translocation can also occur by way of the circulatory system: pathogens that enter the bloodstream through lesions in the mouth or inflamed tissue. Many pathogens can utilize this pathway–known as the hematogenous route of bacterial transmission–to enter the body through even the smallest cuts in your cheeks or gums.
Impacts on the GI System Resulting from Oral Bacteria Translocation
Bacterial translocation from the oral to intestinal microbiome can result in a condition known as gut dysbiosis, or the dominance of one microorganism over the rest of the system. Gut dysbiosis increases vulnerability to GI diseases, as pathogenic bacteria outnumber those that are healthy and protective in the gut. Some well-known conditions resulting from gut dysbiosis include inflammatory bowel disease (IBD), colorectal cancer (CRC), and liver cirrhosis:
IBD is characterized by the swelling of the digestive tract. This condition is most prevalent in Caucasian women in early adulthood. In children, IBD is more common in boys.
CRC starts as an irregular and uncontrolled growth of colon cells. Historically, this type of cancer was thought to be more common in older adults, yet younger people are being diagnosed with CRC more recently. Biological and lifestyle risk factors associated with CRC include obesity and type II diabetes as well as consistent smoking and drinking. Prevalence of CRC is also high in those with majority Native American ancestry.
Liver cirrhosis occurs when the organ must repeatedly self-repair in response to consistent alcohol use, infection, or other stresses. Continuous self-repair causes substantial scarring which decreases the liver’s ability to adequately detoxify and filter blood. Drinking, old age, and obesity are the most common risk factors of liver cirrhosis; prevalence is highest in Hispanic and Caucasian communities.
Preventing and Addressing Bacterial Disease
Maintaining good oral hygiene by brushing teeth twice a day, flossing regularly, and eating healthy foods can significantly strengthen one’s oral-intestinal connection and prevent bacterial diseases, as these practices prevent bacteria from growing and translocating to the gut microbiome. For instance, pre- and probiotics–like yogurts and pickled foods–reduce the risk of bacterial diseases by supporting the gut’s “good” microorganisms that work to keep us healthy.
Patients with severe gum disease–caused by the overcolonization of harmful bacteria in the mouth–may need interventional dental care to improve their oral hygiene and prevent gastrointestinal diseases. Common treatment for people with gum disease is periodontal therapy, which can range from the non-surgical scraping of plaque from the teeth to surgical tissue transfer to the gums. Non-surgical treatments are best suited for more mild cases of periodontal (gum) disease, whereas more severe cases may require surgical intervention. The ultimate goal of periodontal treatments is to rid the mouth and gums of all disease-causing bacteria to prevent its recolonization.
Conclusion
Despite how the oral and gastrointestinal microbiomes differ by unique environmental conditions, they work together to defend against and regulate the onset of many diseases. When their defenses fail, bacteria use the gastrointestinal tract as a highway, translocating from the mouth to the gut and altering internal microbiomes. Evidently, the oral-intestinal connection emphasizes the importance of maintaining good oral health to prevent bacterial translocation and potential disease.
