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HOW DOES GUT MICROBIOME IMBALANCE AFFECT OVERALL HEALTH?
The gut microbiome not only affects digestion but is also linked to the immune system, fatty liver, diabetes, cardiovascular health, and the brain. Join Dr. Mai Vien Phuong, Master’s Degree, Head of the Gastrointestinal Endoscopy Unit at the American International Hospital (AIH), to explore the latest scientific evidence.
How does gut microbiome imbalance affect overall health?
When symptoms go beyond the gut
Recently, Dr. Phuong examined a patient around 50 years old who sought medical attention for prolonged bloating and constipation. She had undergone an upper gastrointestinal endoscopy, a colonoscopy, and various other tests, but the results showed almost no significant abnormalities.
What worried her was not only the discomfort after every meal, but also chronic fatigue, weight gain despite not eating much, and a recent diagnosis of fatty liver.
When asked about her lifestyle habits, she shared that she frequently stays up late to finish work, is sedentary, and has lived in a state of stress for many years.
This is not an uncommon situation at the gastroenterology clinic.
Many people still think that the gut is solely responsible for digesting and absorbing food. However, over the past 15 years, an increasing number of studies have demonstrated that the gut microbiome is closely associated with various other organs and systems in the body. An imbalance in the microbiome not only affects digestive function but can also be linked to the immune system, metabolism, liver health, cardiovascular health, and the brain.
Therefore, when digestive symptoms persist but examination results do not fully explain the cause, taking a holistic view of health including diet, sleep, physical activity levels, stress, and metabolic health can provide important additional perspectives during examination and treatment.
Importantly, correlation does not mean absolute causation. Most chronic diseases are formed by a combination of multiple factors such as genetics, age, diet, physical activity, sleep, and living environment. The microbiome is one of the important pieces of that picture, but it is not the explanation for everything.
The gut microbiome – the silent “resident community” protecting health
Each adult has tens of trillions of microorganisms in their gut, including bacteria, viruses, fungi, and many other microbial groups. Together, they create a diverse ecosystem known as the gut microbiome.
If the body is likened to a city, the microbiome is like millions of residents living and working together.
There are “residents” that help digest fiber, create vitamins, and produce substances beneficial to the intestinal mucosa. There are other “residents” that are always kept at low numbers so they do not cause harm.
A healthy ecosystem is not a place with only good bacteria, but a place where microbial groups maintain a balance with one another.
When this balance is disrupted - also known as dysbiosis - many important functions of the gut begin to be affected.
Not just bloating or constipation
When mentioning the gut microbiome, many people immediately think of symptoms such as:
Flatulence.
Abdominal distension.
Constipation.
Diarrhea.
Indigestion.
Abdominal pain.
It is true that these are the most common manifestations.
However, gastroenterologists notice in clinical practice that quite a few patients have these symptoms yet their endoscopy results are completely normal.
This leaves many people wondering:
“If there are no ulcers or tumors, why do I still constantly feel uncomfortable?”
The answer lies in the fact that endoscopy mainly helps detect structural damage, whereas many disorders related to the microbiome fall into the category of functional disorders.
In other words, the “shape” of the gut may still be normal, but the way it functions has changed.
Microbial imbalance can affect gut motility, increase pain or discomfort, alter food fermentation, and produce more gas. Therefore, patients may still experience bloating, abdominal distension, discomfort, or changes in bowel habits, even though tests have not recorded any clear physical lesions.
This is also why many people with irritable bowel syndrome (IBS) or functional digestive disorders are commonly noted to have alterations in their gut microbiota.
From clinical practice
Quite a few patients, after learning they might be experiencing dysbiosis, have proactively bought and used various types of probiotics in the hope of improving their symptoms.
However, after some time, manifestations such as bloating, bowel irregularities, or gut discomfort have not significantly improved.
When probing more deeply into lifestyle and daily habits, gastroenterologists notice that the problem sometimes does not lie solely with the microbiome. Prolonged sleep deprivation, irregular eating habits, work stress, or frequent consumption of processed foods can also be factors affecting gut health.
This indicates that one should not merely focus on supplementing probiotics while ignoring the foundational factors impacting the digestive system every day. A more comprehensive approach, ranging from nutrition, sleep, and physical activity to stress management, can play an important role in supporting microbiome balance and improving gut health.
The microbiome and the immune system – the body's “training class”
Few people know that about 70% of the body's immune cells are concentrated in the gastrointestinal tract.
This is not a coincidence.
Every day, the gut must come into contact with millions of microorganisms and countless food components. The immune system needs to learn how to distinguish between beneficial bacteria, pathogenic bacteria, and simple food proteins.
The microbiome plays the role of a “teacher” helping the immune system learn that.
Beneficial bacteria also contribute to strengthening the protective barrier of the intestinal mucosa. This mucosal layer acts like a “control gate,” allowing only nutrients to pass through while restricting bacteria and toxins from entering the bloodstream.
When the microbiome is unbalanced, this barrier can function less effectively. Certain bacterial components can pass through the intestinal mucosa more frequently, stimulating an immune response and creating a state of prolonged low-grade inflammation.
Some studies show that the interaction between the microbiome, the mucosal barrier, and the immune system may be related to many chronic pathologies. However, the extent of the impact and the specific role of the microbiome in each disease are still being actively researched by scientists.
Understand correctly to avoid wrong treatment
There is no evidence that the more probiotics you consume, the healthier your immune system becomes.
A healthy immune system requires the coordination of many factors such as a diverse diet, adequate sleep, regular physical activity, stress management, and using antibiotics only when truly necessary.
Fatty liver and the “gut-liver axis”
The liver is closely connected to the gut through the portal venous system - the pathway that carries blood from the digestive organs directly to the liver. Therefore, after being absorbed in the gut, nutrients along with certain metabolic products produced by the microbiome are also transported to the liver.
This connection is called by scientists as the “gut-liver axis.”
In a healthy state, the microbiome and the intestinal mucosal barrier jointly contribute to maintaining balance, restricting the vast majority of bacteria and potentially harmful substances from crossing the intestinal barrier into circulation.
However, fatty liver is a condition associated with many factors such as diet, weight, physical activity, and metabolism. Therefore, gut microbiome imbalance should not be viewed as the sole cause, but rather health needs to be evaluated comprehensively.
Conversely, when the microbiome is unbalanced, intestinal mucosal permeability can increase. Certain bacterial components, such as lipopolysaccharides (LPS), can cross the gut barrier and reach the liver in greater amounts. This has the potential to trigger inflammatory responses and contribute to the formation or progression of metabolic dysfunction-associated steatotic liver disease (MASLD).
Many studies show that people with fatty liver often have a different gut microbiota compared to healthy individuals. However, to date, it cannot be confirmed that microbiome imbalance is the direct cause of the disease.
Instead, experts believe that fatty liver is the result of a combination of multiple factors such as an energy-rich diet, overweight, obesity, physical inactivity, insulin resistance, genetic factors, and alterations in the microbiome.
A healthier liver starts with small changes
Quite a few patients are surprised when advised that improving fatty liver is not merely about losing weight. Alongside weight management, changes in diet and lifestyle also play a crucial role in the health of both the liver and the gut.
A diverse diet, prioritizing green vegetables, fruits, legumes, and whole grains, combined with regular physical activity and adequate sleep, not only supports metabolic control but also creates a favorable environment for the gut microbiome to maintain diversity and balance.
These are relatively simple changes that need to be maintained long-term. When caring for health, the gut and the liver should not be viewed as two completely separate organ systems, but rather considered in connection with each other and with overall health.
Caring for the gut is also a part of caring for overall health
The gut microbiome is not just a private matter of the digestive system. From the immune system and metabolism to the health of the liver and the brain, an increasing number of studies have demonstrated the connection between the gut and various organs throughout the body.
However, not all symptoms stem from microbiome imbalance, and simply supplementing with probiotics does not solve the problem. When digestive symptoms persist or recur, patients should be examined to find the cause rather than engaging in prolonged self-treatment.
At the Department of Gastroenterology – American International Hospital (AIH), doctors approach patients based on symptoms, medical history, lifestyle habits, and risk factors to provide appropriate evaluation and treatment. Because a healthy digestive system not only helps you eat well and digest well, but is also an important part of long-term health.
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