In recent years, a major buzzword in medical research has emerged: the microbiome . This refers to the trillions of microorganisms that live in and on our bodies – and which exert far more influence than long suspected. The focus is particularly on the intestinal microbiome, which can control our digestion, immune system, and even our psyche. But the microbiome in the mouth is also crucial to our health. It is becoming increasingly clear that the mouth and intestines are in constant dialogue. Diseases or disorders at one end of the digestive tract can affect the other.
In this article, we want to delve deep into the science and understand how oral health influences the gut—and why, conversely, a healthy gut also strengthens the oral flora. At the same time, we'll take a look at new approaches to using this knowledge for prevention and treatment.
The oral cavity as an entry gate
The mouth is not only the first organ to come into contact with food, but also the gateway to the digestive tract. This is where the mechanical grinding by the teeth and the initial chemical digestion by enzymes in saliva begin. At the same time, more than 700 different species of bacteria thrive in the oral cavity. Some of these are beneficial, while others can cause disease under certain circumstances.
With every swallow, billions of microorganisms enter the digestive tract from the oral cavity. Normally, stomach acid kills many germs. But certain bacteria are resistant enough to overcome this barrier and reach the intestines. This creates a direct connection: the oral microbiome influences the composition of the intestinal microbiome.
When mouth germs migrate into the intestine
In recent years, researchers have increasingly investigated how bacteria from the mouth enter the gut and how they affect it. This is particularly evident in periodontitis , a chronic inflammation of the periodontal ligament. Certain anaerobic bacteria, including Porphyromonas gingivalis , multiply in the mouth . Studies show that these bacteria are detectable not only in the mouth but also in the gut. There, they can disrupt the balance of the microbiome, promote inflammation, and potentially worsen chronic intestinal diseases.
Similar associations have been found in Crohn's disease and ulcerative colitis . Patients with these diseases often have oral bacteria in their intestines that are not normally found there. This suggests that an unhealthy oral flora can increase the risk of intestinal inflammation or worsen existing problems.
Inflammation as a common interface
Inflammatory processes play a central role in both the mouth and the gut. Chronic gingivitis can increase systemic inflammatory markers in the blood. These, in turn, affect the entire body – including the intestinal mucosa. Conversely, inflammatory processes in the gut can influence the immune system in the mouth. This explains why people with chronic inflammatory bowel disease are often more susceptible to gingivitis or oral infections.
Inflammation is therefore the common interface through which the mouth and intestines are closely connected.
The influence of intestinal flora on oral health
But the connection doesn't just work in one direction. The composition of the intestinal flora also affects the mouth. The intestine is a central control organ for the immune system. If the intestinal microbiome is disrupted—for example, due to an unbalanced diet, antibiotics, or chronic diseases—this affects the entire body's immune system. This makes it easier for pathogenic bacteria to take over in the mouth.
One example is oral fungal infections . People with an imbalanced gut flora are often more susceptible to Candida albicans , a yeast fungus that can cause oral thrush. Periodontitis also appears to occur more frequently when the gut flora is unbalanced.
Mouth and intestine in dialogue: The entero-oral circulation
Scientists are increasingly talking about the entero-oral circulation . This refers to the mutual influence of the oral and intestinal microbiomes. Various mechanisms play a role:
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Migration of bacteria : Oral germs can reach the intestines and colonize there. Conversely, bacteria from the intestines can enter the oral cavity via the bloodstream.
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Immune system : Changes in the intestine influence the systemic immune defense – and thus also the reactions in the mouth.
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Metabolic products : Intestinal bacteria produce short-chain fatty acids and other metabolites that can affect the oral cavity.
This interaction makes it clear: oral and intestinal health cannot be viewed in isolation.
Nutrition as a key factor
A crucial factor that shapes both the oral and intestinal flora is diet. A diet rich in sugar promotes cariogenic bacteria in the mouth and pro-inflammatory bacteria in the intestines. Fiber, on the other hand, has the opposite effect: It supports the formation of short-chain fatty acids like butyrate in the intestines, which have anti-inflammatory effects. At the same time, fiber-rich foods promote a more balanced flora in the mouth.
Fermented foods such as yogurt, sauerkraut, or kefir also provide probiotic bacteria that can have positive effects both in the gut and the mouth. Studies show that certain probiotics not only stabilize the intestinal flora but also help fight tooth decay and gum disease in the mouth.
Probiotics: Double action for mouth and intestines
Probiotics are one of the most exciting research areas in this context. Preparations containing live bacterial cultures such as Lactobacillus reuteri or Streptococcus salivarius were originally developed primarily to support intestinal health. However, it is now known that they can also have a positive effect on the oral flora.
Probiotic lozenges or chewing gums have been shown to reduce the risk of gingivitis. At the same time, the same bacteria in the gut contribute to strengthening the barrier function and reducing inflammation. Thus, probiotics have a kind of dual effect, making them a promising tool for prevention.
The influence of antibiotics
While probiotics can have positive effects, antibiotics often have the opposite effect. These medications are essential for fighting bacterial infections, but they also attack the beneficial bacteria in the body. Taking antibiotics for a long time severely disrupts both the intestinal and oral flora. Common consequences include diarrhea, fungal infections in the mouth, and an increased susceptibility to tooth decay and periodontitis. This makes it all the more important to specifically support the rebuilding of the flora after antibiotic therapy.
Stress, psyche and the microbiome
Another factor that affects both the mouth and the gut is stress. Chronic stress alters hormone levels, weakens the immune system, and alters the composition of the microbiome. Some researchers speak of a mouth-gut-brain axis , which demonstrates how closely intertwined the psyche, digestion, and oral health are. Stress-related digestive problems can therefore also be felt in the mouth—and vice versa.
Practical consequences
Knowledge of the close connection between the mouth and the gut opens up new possibilities in prevention and treatment. Dentists and gastroenterologists should work more closely together when patients struggle with both periodontitis and chronic intestinal diseases. Nutritional therapies that strengthen the gut can also improve oral health. Conversely, consistent oral hygiene can reduce the risk of intestinal diseases.
In everyday life, this means that those who pay attention to a healthy diet, balanced oral hygiene and the targeted use of probiotics not only protect their teeth and gums but also strengthen their intestinal health.
Conclusion
The mouth and gut are more closely connected than was long assumed. Both systems influence each other through microorganisms, inflammatory processes, and the immune system. Disturbed oral flora can disrupt the balance of the gut—and disturbed gut flora, in turn, affects oral health. Anyone who thinks oral hygiene is only important for the teeth is mistaken. It is part of a holistic health strategy that affects the entire body. Supporting the gut through a healthy diet, probiotics, and stress management is equally crucial.
The insight: A healthy mouth begins in the gut – and a healthy gut begins in the mouth.
FAQ: Frequently Asked Questions
Can bacteria from the mouth really survive in the intestines?
Yes, certain bacteria are resilient enough to survive stomach acid and colonize the intestines. Studies have detected Porphyromonas gingivalis, for example , in both the oral cavity and the intestines.
Does periodontitis affect my digestion?
Indirectly, yes. Inflammatory processes in the mouth can put strain on the intestines and increase the risk of chronic intestinal diseases or worsen existing symptoms.
Can probiotics work for the mouth and gut at the same time?
Absolutely. Certain strains, such as Lactobacillus reuteri , can stabilize the oral flora, strengthen the intestinal barrier, and reduce inflammation.
How do I know if my intestinal flora is disturbed?
Common signs include digestive problems, bloating, diarrhea, or constipation. Oral problems such as frequent bad breath or gingivitis can also indicate an imbalance.
Does a high-fiber diet also help with oral health?
Yes. Fiber promotes beneficial bacteria in the gut and has an anti-inflammatory effect. At the same time, it also supports a more balanced flora in the mouth and reduces the risk of tooth decay and gum disease.
