Dietary fiber is anything but "ballast". It consists of indigestible plant fibers that are crucial for healthy digestion and long-term health.
Why is dietary fiber important?
Dietary fiber fulfills several key functions in the body:
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Digestion & Gut Health: They bind water in the intestines, swell up, and stimulate bowel movements. Above all, they serve as "food" for beneficial gut bacteria, which strengthens the intestinal flora.
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Longer-lasting satiety: Because high-fiber foods usually require more chewing and swell in the stomach, the feeling of fullness lasts longer. This helps with weight management and prevents cravings.
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Blood sugar levels: Dietary fiber ensures that carbohydrates are absorbed into the bloodstream more slowly. This prevents sharp blood sugar spikes after meals, which can have a detrimental long-term impact on overall health.
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Cholesterol reduction: Some dietary fibers can bind and excrete bile acids, forcing the body to produce new bile acids from cholesterol – thereby lowering the cholesterol level in the blood.
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Prevention: A diet rich in fiber statistically reduces the risk of cardiovascular disease, high blood pressure, and colon cancer.
Fiber and gut health
For a long time, dietary fiber was considered merely an indigestible component of our food, whose sole purpose was to mechanically keep digestion running smoothly. Today we know: This view is long outdated. Dietary fiber is essential for our long-term health and plays a key role in a fascinating internal ecosystem – our gut.
But how exactly do these plant fibers from vegetables, nuts and root tubers affect our bodies?
The microbiome: food for our inner allies
Our gut is home to trillions of microorganisms, the so-called microbiome. These bacteria are not passive inhabitants, but are crucial for our immune system and our mood. This is where dietary fiber comes into play: it is the preferred "food" (prebiotics) for our beneficial gut bacteria.
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Selective feeding: Dietary fiber primarily feeds beneficial bacteria strains (e.g., bifidobacteria and lactobacilli).
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Displacement: When the good bacteria are well fed and multiply, they leave no room for disease-causing germs (pathogens).
Since humans lack the enzymes to completely break down these fibers, they reach the large intestine. There, beneficial bacteria ferment them. This process produces vital metabolic products, especially short-chain fatty acids like butyrate (butyric acid). These fatty acids have anti-inflammatory effects throughout the body and regulate metabolism .
The intestinal mucosal wall: The protective shield against invaders
Our gut health is often determined unseen. A key player in this process is butyrate (also known as butyric acid). But what exactly is it?
Butyrate can be thought of as the "super fuel" for our intestines. It is a short-chain fatty acid that is not directly present in our food, but is produced in our bodies. When we eat fiber-rich foods such as vegetables, legumes, or whole grains, these fibers pass undigested into the large intestine. There, they are fermented by our beneficial gut bacteria – and butyrate is produced as a valuable "byproduct" of this process.
Butyrate's most important function lies directly at the site of action: it serves as the primary energy source for the cells of our intestinal lining. You can think of it like the mortar between the bricks of a wall:
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Strong barrier: A well-nourished intestinal lining is thick and resilient. It forms a crucial boundary that allows vital nutrients to pass through, but consistently repels harmful substances, toxins, and pathogens.
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Protective mucus: Butyrate also stimulates the production of mucus, which coats the intestinal wall like a protective film.
Types of dietary fiber
For a healthy gut, we need two types of fiber, as they have different functions:
A) Insoluble fiber (The “broom”)
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Lectin-free sources: Macadamia nuts, leafy greens, coconut, mushrooms, asparagus
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Function: They are hardly decomposed by bacteria. They absorb water and swell considerably.
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Effect: They increase stool volume. A larger volume presses against the intestinal wall, which stimulates peristalsis (muscular movement of the intestines). Transit is accelerated.
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Why this is important: The shorter the time the stool remains in the intestine, the shorter the contact time of the intestinal wall with potentially carcinogenic substances and toxins.
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B) Soluble dietary fiber (The “gel”)
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Lectin-free sources : psyllium husks, apples (pectin), acacia fiber, sweet potatoes, cabbage and root vegetables, berries.
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Function: They form a gel with water.
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Effect: This gel softens the stool. It also binds bile acids and toxins and transports them out of the body. Soluble fiber is also the main food source for the bacteria mentioned above.
When fiber is lacking
A lack of dietary fiber deprives bacteria of food and thus the basis for butyrate production. As a result, the cells of the intestinal wall "starve," and the barrier becomes permeable. This condition is known in the scientific community as "leaky gut syndrome."
These tiny gaps allow substances to enter the bloodstream that don't belong there. This is now linked to chronic inflammation and various lifestyle diseases. Dietary fiber thus indirectly helps keep your body's internal protective barrier intact and relieves the burden on your immune system.
This means the intestinal flora starves: If the good bacteria lack food, they die.
"If you don't feed them, they'll eat you."
Remaining bacteria switch to an "emergency food source".
The protective mucus layer of the intestine (the mucosa) is chemically composed of very similar structures to plant fibers: complex carbohydrate chains (so-called mucins/glycoproteins). For bacteria, this protective layer is therefore nothing more than a substitute buffet.
The three phases of "self-digestion"
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Metabolic shift: Special types of bacteria (so-called mucin degraders such as Akkermansia muciniphila ) multiply and begin to produce enzymes that dissolve the mucus.
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The wall is crumbling: The mucus layer is becoming measurably thinner. Studies have shown that this can happen after only a short time (a few days of a fiber-free diet).
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Leaky gut & inflammation: The mucus layer is the barrier that prevents gut bacteria from directly touching the intestinal wall. If it is eroded, bacteria come into direct contact with the human intestinal cells. This immediately alerts the immune system: inflammation ensues.
Why is this so dangerous?
This process opens the door to pathogens. The imbalance in the composition of good and bad gut bacteria is called dysbiosis. Animal models have shown that organisms with a mucosa "eaten away" by a lack of dietary fiber die much more quickly from intestinal infections because their first line of defense is missing.
The good news:
The process is reversible. The intestinal lining is constantly renewing itself. As soon as you reintroduce fiber ("prebiotics"), the bacteria will again prefer the easy prey from the food pulp and allow the intestinal wall to heal undisturbed. Actively rebuilding the gut flora with probiotics or incorporating fermented foods into your diet may be helpful to repopulate the gut. Otherwise, fiber that has no takers could lead to bloating and discomfort.
Dealing with lectins
An intact mucus layer is also our best protection against lectins. Lectins are proteins that plants produce as a defense against herbivores. They are found in many plant-based foods, particularly concentrated in legumes and grains.
Some lectins can irritate the intestinal wall and adhere to intestinal cells, which can further increase permeability. This is particularly noticeable in people with already damaged intestines or those with lectin sensitivity. Unfortunately, this is often not noticeable immediately after eating, but rather manifests gradually through various inflammatory processes in the body, resulting in a range of symptoms. A healthy, fiber-rich gut is therefore much better able to cope with lectins.
A brief note on antinutrients:
Lectins, along with phytic acid and oxalates, are often referred to as "antinutrients" because they can inhibit the absorption of certain minerals. However, it's important not to use these substances as a reason to completely eliminate healthy, fiber-rich foods from your diet. With proper preparation and a good selection of foods, they are rarely problematic for a healthy gut.
Lectin-free fiber sources
Traditional methods such as soaking, sprouting, fermenting and especially pressure cooking effectively break down most aggressive lectins (such as those found in raw beans).
It is important to use the correct method for eliminating lectins , as not all lectins are the same. More information can be found here . This also applies to other antinutrients.
The health benefits of a plant-based, high-fiber diet far outweigh the potential disadvantages of these substances.
