The term leaky gut comes up more and more often when we talk about gut health, inflammation, and the immune system. But what exactly is “leaking”? And how can something that happens in the gut affect the rest of the body?
Leaky gut is the popular term for increased intestinal permeability, which means that the intestine's protective barrier has become more permeable than it normally should be. To understand why this matters, we first need to understand the remarkable function of the intestinal lining.
The gut is more than a digestive organ
When we eat, food enters the gastrointestinal tract, where it is broken down into smaller components that the body can use. But not everything inside the intestine should be allowed to pass out into the body.
That is why there is a thin but advanced protective barrier between the contents of the intestine and the rest of the body: intestinal lining.
You can think of it as a very careful doorman. It should allow things the body needs, such as water, minerals, and broken-down nutrients, to pass through, while helping keep bacteria, larger particles, and other unwanted substances on the right side.
When this barrier functions well, it is therefore not completely closed; it is selective. The problem arises when this control deteriorates.
What happens with leaky gut?
The cells that make up the intestinal wall lie close together. Between them are structures commonly known as tight junctions, rather like small doors or locks between the cells. These help the body control what is allowed to pass through the gut barrier.
With leaky gut, the barrier does not function as effectively. Substances from the gut can then come into contact more easily with the immune system on the other side of the intestinal lining.
A large part of the body's immune system is connected to the gut. This makes sense: the gut is one of the body's largest points of contact with the outside world. If the gut barrier is disrupted, the immune system may therefore be activated. If this continues over a longer period, it may contribute to a more inflammatory environment. This is one reason why research into the gut barrier now extends far beyond classic digestive problems.
What can affect the gut barrier?
Leaky gut rarely arises for just one reason. It often involves several factors that affect the gut environment over an extended period.
1. Dysbiosis – an imbalanced gut microbiota
The gut bacteria and intestinal lining work together. When we eat fiber, our gut bacteria can ferment it and produce short-chain fatty acids. One of the most studied is butyrate (butyric acid). Butyrate functions, among other things, as fuel for cells in the colon and is involved in the normal function of the gut barrier.
If the gut microbiota changes and the number of beneficial fiber-fermenting bacteria decreases, the production of these substances may also change. That is why dysbiosis and an impaired gut barrier are often seen as two parts of the same broader gut environment.
2. A low-fiber diet
Our gut bacteria need food, and an important part of their food comes from fiber. Vegetables, fruit, berries, legumes, whole grains, nuts, and seeds contain different types of fiber that reach the colon and can be used by the bacteria.
A long-term low-fiber diet can therefore change both the gut microbiota and the substances produced by the bacteria. But this does not mean that a sensitive stomach should go from very little fiber to huge amounts overnight. In cases of severe digestive problems, fiber intake may need to be increased slowly.
The goal is to gradually create an environment in which the gut and gut microbiota have better conditions to function.
3. Alcohol and a nutrient-poor diet
Alcohol and a diet high in processed foods and low in fiber-rich foods can also affect the gut environment. This is why gut health is rarely about a single “superfood” or dietary supplement. The long-term dietary pattern is much more important.
4. Stress
The gut and brain communicate with each other continuously through the gut–brain axis. Long-term stress can affect gut motility, the immune system, the gut microbiota, and barrier function. This is why two people can eat roughly the same diet yet have completely different digestive function. Supporting the gut is therefore not just about food. Sleep, recovery, movement, and stress management are also important parts of the whole picture.
5. Infections and certain medications
Gastrointestinal infections can temporarily alter both the gut microbiota and the intestinal lining. Certain medications can also affect the gastrointestinal tract and its barrier. This does not mean that necessary medications should be avoided. However, it is another example of why the gut environment is influenced by much more than the food we eat.
What symptoms can leaky gut cause?
It is easy to think that an unhealthy gut must always cause obvious digestive symptoms. But the gut communicates with large parts of the body, including the immune system, skin, and brain.
When the gut barrier becomes more permeable, substances from the gut can come into contact with the immune system more easily. This can activate immune responses and contribute to a more inflammatory environment in the body. This is one reason why researchers are now studying the gut barrier in connection with significantly more conditions than just IBS and other gastrointestinal problems.
Altered gut microbiota and barrier function have been linked, among other things, to:
- Skin problems – there is clear communication between the gut and the skin, known as the gut–skin axis. Dysbiosis and altered barrier function are being studied, among other conditions, in eczema and psoriasis.
- Autoimmune diseases – the gut barrier plays an important role in communication between the gut microbiota and the immune system. Increased intestinal permeability has been observed in several autoimmune and inflammatory diseases, including celiac disease, inflammatory bowel disease, type 1 diabetes, and rheumatoid arthritis.
- Depression and anxiety – the gut and brain communicate through the gut–brain axis. Research is investigating how the gut microbiota, immune system, stress system, and gut barrier may be involved together in depression and anxiety.
- Fatigue and low energy – dysbiosis has also been linked to chronic fatigue, where inflammation and altered communication between the gut, immune system, and brain may be part of the picture.
However, not everyone who has eczema, fatigue, depression, or an autoimmune disease has a leaky gut, and the gut is not always the sole cause of these conditions. The body is considerably more complex than that.
But it shows why the gut should not be viewed as an isolated digestive organ. When the environment in the gut changes, communication with the immune system and other parts of the body can also change. That is why gut health can be relevant even for people who do not walk around with constant stomach pain or bloating.
Can leaky gut be healed?
The intestinal lining is dynamic tissue that is constantly maintained and renewed. Therefore, it is more helpful to think about create the right conditions for a well-functioning gut barrier than looking for a quick fix. And this brings us back to the gut ecosystem.
Feed the gut microbiota
A varied, plant-based, fiber-rich diet provides gut bacteria with raw materials for producing compounds such as butyrate. Feel free to vary your intake of vegetables, root vegetables, legumes, whole grains, fruit, berries, nuts, and seeds.
Eat a wide variety of plants
Different bacteria prefer different types of fiber. Therefore, variety may be at least as important as focusing on the amount of fiber. Think about colors, different plant families, and variety throughout the week.
Remember polyphenols
Berries, colorful vegetables, herbs, spices, cocoa, tea, and many fruits contain polyphenols. These plant compounds interact with the gut microbiota and are another reason why variety in the plant kingdom is valuable for the gut environment.
Take care of the nervous system
A gut that is constantly in a stressed body has different conditions from a gut in a body that regularly gets time to recover. Sleep, daylight, physical activity, time in nature, relaxed meals, and stress management can be an important part of supporting gut health.
The gut does not need perfection; it needs the right environment
When people hear the term leaky gut, it is easy to start looking for things to remove. Gluten must go. Lectins must go. Legumes must go. Grains must go. But the more fiber-rich foods we remove, the less variety our gut bacteria also have to work with.
For some people and in certain medical conditions, specific foods may of course need to be limited for a period. But in general, a strong gut environment is not only about what we remove, but at least as much about what we add.
The gut is not a static barrier. It is living tissue that constantly communicates with our bacteria, our immune system, and the rest of the body. And perhaps that is precisely why gut health is so fascinating:
When we take care of the environment in the gut, we also give the gut better conditions to take care of us.
