Scientists discovered that a specific type of bacteria living in your mouth might be connected to a serious liver condition called fatty liver disease. Researchers compared the mouth bacteria of 21 people with fatty liver disease to 20 healthy people and found important differences. They identified one bacterium called Actinomyces naeslundii that was much more common in people with the disease. When they gave this bacterium to mice, it made their fatty liver disease worse. This discovery suggests that keeping your mouth bacteria healthy might be important for protecting your liver.
The Quick Take
- What they studied: Whether specific bacteria living in your mouth are connected to fatty liver disease and if one particular bacterium makes the condition worse
- Who participated: 21 adults with fatty liver disease and 20 healthy adults. Researchers also tested the findings in mice to understand how the bacteria affects the liver
- Key finding: A mouth bacterium called Actinomyces naeslundii was found in much higher amounts in people with fatty liver disease compared to healthy people. When this bacterium was given to mice, it made their fatty liver disease significantly worse
- What it means for you: This suggests that the health of bacteria in your mouth may be connected to liver health. While this is early research, it hints that good oral hygiene and mouth health might help protect your liver. However, more research in humans is needed before making specific recommendations
The Research Details
Researchers collected plaque samples from the teeth of 21 people with fatty liver disease and 20 healthy people. They used advanced genetic testing to identify and count all the different bacteria living in their mouths. They then took the bacteria they found and tested it in mice to see if it actually caused fatty liver disease to get worse. This two-step approach—first studying humans, then testing in animals—helps scientists understand if a connection is real and how it works.
This study design is important because it combines real-world observations from people with laboratory experiments in animals. This helps researchers move beyond just noticing a pattern to actually proving that the bacteria causes problems. The mouse experiments are crucial because they show that the bacteria doesn’t just appear with the disease—it actually makes the disease worse
This is a preliminary study with a relatively small number of human participants (41 total), so the findings need to be confirmed in larger groups of people. The mouse experiments provide strong evidence that the bacteria can cause harm, but mice don’t always respond exactly like humans do. The research was published in a peer-reviewed journal, meaning other scientists reviewed it for quality. However, this is early-stage research that needs follow-up studies before doctors can make treatment recommendations
What the Results Show
The study found that people with fatty liver disease had fewer types of bacteria in their mouths compared to healthy people—meaning less diversity. The bacteria that were present were different types and amounts than in healthy mouths. Importantly, one specific bacterium called Actinomyces naeslundii was found in much higher amounts in people with fatty liver disease. This bacterium was so strongly connected to the disease that it could potentially be used as a warning sign that someone might have fatty liver disease. When researchers gave this bacterium to mice eating a high-fat diet, the mice developed worse fatty liver disease. The bacteria also changed the types of bacteria living in the mice’s stomachs and intestines, suggesting the mouth bacteria affects the whole digestive system
The study identified seven different bacteria species that might serve as markers for fatty liver disease. The researchers found that bacteria in the mouths of people with fatty liver disease were more connected to each other—they worked together more—compared to bacteria in healthy mouths. This suggests the disease creates an environment where certain bacteria thrive and work together in ways that might be harmful
Previous research has shown that gut bacteria (bacteria in your stomach and intestines) play a role in fatty liver disease. This study adds new information by showing that mouth bacteria might also be important. It supports the growing understanding that bacteria throughout your body—not just in your gut—affect your liver health. This fits with the idea of the ‘oral-gut axis,’ which means your mouth bacteria can influence your gut bacteria and overall health
The human study included only 41 people, which is a small group. To be confident in these findings, researchers would need to study hundreds or thousands of people. The study was done at one point in time, so researchers couldn’t follow people over months or years to see how the bacteria changes. The mouse experiments, while helpful, don’t perfectly mirror what happens in human bodies. The study shows a connection between this bacterium and fatty liver disease but doesn’t prove it’s the only cause—fatty liver disease is complex and likely involves many factors
The Bottom Line
Based on this early research, there are no specific medical recommendations yet. However, maintaining good oral hygiene through regular brushing, flossing, and dental checkups is always beneficial. If you have fatty liver disease or are at risk, talk to your doctor about all factors affecting your liver health, which may eventually include oral health. This research suggests that future treatments might target mouth bacteria, but that’s not available yet
People with fatty liver disease or those at risk (overweight, diabetic, or with metabolic problems) should be aware of this research. People with poor oral health should know this is another reason to improve it. However, this research is too early to change treatment plans. Anyone with liver disease should continue following their doctor’s current recommendations
This is very early research. It will likely take several years of additional studies in humans before doctors might recommend treatments based on these findings. Don’t expect changes to medical practice immediately, but this opens a promising new direction for research
Want to Apply This Research?
- Track daily oral hygiene habits (brushing twice daily, flossing) and note any changes in energy levels or digestive symptoms. Users could also log dental visits and any feedback from dentists about plaque buildup or gum health
- Set reminders for twice-daily tooth brushing and daily flossing. Schedule regular dental cleanings every 6 months. If you have fatty liver disease, discuss with your dentist whether more frequent cleanings might be beneficial based on emerging research
- Monitor consistency of oral hygiene routines over weeks and months. Track dental health improvements noted by your dentist. For those with fatty liver disease, work with your doctor to monitor liver health markers while maintaining excellent oral hygiene as part of overall health management
This research is preliminary and has not yet been tested extensively in humans. The findings suggest a potential connection between mouth bacteria and fatty liver disease but do not establish definitive cause-and-effect in people. This information should not be used to diagnose, treat, or prevent any disease. If you have fatty liver disease or concerns about your liver health, consult with your healthcare provider about appropriate screening and treatment options. Do not change your current medical treatment based on this research. Future studies are needed to confirm these findings and determine if treatments targeting mouth bacteria would be safe and effective for humans.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.