The microorganism population of the human mouth is one of the most complex microbial communities in the body, to the count of somewhere between 700-2000 different types. The especially interesting thing is not the long, fancy names that they have, but what systemic or whole-body conditions that different ones can be associated with. It is their close relationship that is being studied more now than ever, and may give us a new target for the treatment of certain diseases.
Diet patterns affect bacterial types in the mouth, and big differences have been noted between thriving bacteria in vegetarians versus hunter-gatherers (lots of meat) versus traditional farmers (who are in between those two). An example of how what you eat can govern microbial species is through catechins (found in green tea), which were noted to shift prevalence of bacteria to decrease cancer risk in smokers. Another example is polyphenols (in grapes/red wine, cherries, apples) which somehow decrease the count of Streptococcus mutans that is a main component of dental plaque that causes caries (“cavities”) in teeth. They can also decrease the inflammatory response in the gum tissue with periodontitis. So it appears that maybe an apple a day really does keep the dentist away…
In case you are interested, specific bacteria that cause cavities are Prevotella, Lactobacillus, Dialister, Filifactor, while bacteria linked to gum disease are Clostridium, Porphyromonas, Helicobacter, Actinomycetes, Eugenia, Carbachia, and Micromonas. The imbalance of the bacteria with healthy ones appears to increase local inflammation perhaps through an increase in memory Th17 cells in the oral tissues.
So if the oral bacteria are so closely tied to what happens in the rest of the body, how do they get from the mouth to cause problems in other areas? The answer can be one of three routes:
- Through the esophagus – directly moving down to invade the gut
- Through the periodontal blood (“blood cycling”) to enter the systemic circulation of the entire body
- Through the bloodstream as metabolites or products of the oral bacteria – causes the body to exist in a low-grade inflammatory state
Here listed are just a few of the known connections between specific oral bacteria and systemic conditions:
- Diabetes – Aggregatibacter, Neisseria, Mycobacterium and Eikenella
- Obesity – Plasmodium, Staph genius, Strep mutans
- Liver disease – detection of oral bacteria Clostridium and Oribacterium in the saliva can assist in the diagnosis of liver cancer without surgery
- Colon cancer – F. nucleatum in the mouth can go elsewhere though blood cycling and indirectly promote colonic tumor formation
- Pancreatic cancer – P. gingivalis in the oral cavity suggests a high risk of pancreatic cancer by promoting a pathway for cytokines and thereby local inflammation and tumorgenesis
- Rheumatoid arthritis – Lactobacillus salivarius, Atopobium, Leptotrichia, and Prevotella
For now, as we continue to learn more, the best things we can do are to promote whole body health (such as through diet and physical activity), use oral probiotics, and locally achieve bacterial homeostasis with such things as xylitol gum.