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Soluble Fiber—Good Food for Gut Bacteria

Unlike probiotics, prebiotics are not living microorganisms, but rather “food” for the good gut bacteria. They are special types of soluble dietary fiber that the human body cannot break down with its own enzymes. They therefore reach the large intestine undigested, where they serve as food for the bacteria. Soluble dietary fiber promotes the growth of good bacteria while simultaneously suppressing harmful pathogens. It also supports healthy digestion and regular bowel movements, thereby promoting our overall well-being.

The breakdown of soluble fiber—also known as fermentation—produces short-chain fatty acids such as acetic acid and butyric acid. These metabolic byproducts help maintain a healthy acidic environment in the gut. In addition, butyric acid in particular serves as an energy source for the intestinal mucosa, thereby strengthening the intestinal barrier. Because fermentation naturally produces gases, slowly fermentable dietary fibers—such as guar gum, acacia fiber, or resistant dextrin—are better tolerated.

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What is soluble fiber?

Soluble dietary fiber, also known as prebiotics , consists of components found in plant-based foods that the human body cannot break down with its enzymes. Our digestive enzymes can only break down carbohydrates, fats, and proteins. As a result, soluble fiber passes undigested through the stomach and small intestine into the large intestine. It dissolves in the aqueous environment of the intestine, where it can be broken down by gut bacteria. It thus serves as food for them—gut bacteria cannot survive without soluble fiber.

Different enzymes are sometimes required to break down these various types of soluble fiber. In fact, some bacterial strains are equipped with different enzymes—so each bacterial strain has its own preference for the appropriate soluble fibers.

Soluble Fiber For example, in

Pectin

Citrus and apple pectin powder, flaxseed

Inulin

Artichoke, Jerusalem artichoke

α-Gluco-oligosaccharides

Legumes

Fructo-oligosaccharides (FOS)

Bananas, rye, tomatoes, asparagus, garlic, onions

resistant dextrin

Corn, potatoes, wheat

Arabino-galacto-saccharides

Acacia fiber

Guar

Guar gum, guar bean (Cyamopsis tetragonolobus, a type of Indian bean)

Carob flour

Carob Tree Seeds

Beta-glucan

Oats, barley, oat bran

Lactulose

heated or aged milk

What are prebiotics and soluble fiber good for?

When soluble dietary fiber is broken down, lactic acid and/or short-chain fatty acids such as butyric acid, acetic acid, and propionic acid, as well as gases, are produced—depending on the bacterial strain. Lactic acid and short-chain fatty acids are important for maintaining a healthy, acidic pH level in the gut. The pH level of stool should be between 5.8 and 6.5. The gases also help soften the stool.

Soluble dietary fiber, as well as its breakdown products formed during fermentation, are beneficial for the gut and the entire body. Their primary effects include:

  • Strengthening the gut flora by promoting the growth of beneficial bacteria (e.g., lactobacilli, bifidobacteria)
  • Acidification and, consequently, improvement of the intestinal environment (acidic pH) to ward off harmful pathogens
  • Strengthening the intestinal mucosa with the help of short-chain fatty acids, especially butyrate, as an energy source
  • Improving the absorption of minerals such as calcium, sodium, magnesium, and phosphorus
  • Improved bowel movements
  • Strengthening of the immune system
  • Promotion of hormone production in the gut (serotonin as a precursor to melatonin, dopamine, and GABA)
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A High-Fiber Diet — The Most Important Foods

Soluble fiber is found in plant-based foods, especially fruits and vegetables. Foods that are particularly rich in this type of fiber include:

  • Artichokes
  • Garlic
  • Onions
  • Leeks
  • Asparagus
  • Chicory roots
  • Beets
  • Bananas
  • Apples
  • Plums
  • Apricots

Soluble Fiber: Which Types Are Easily Digested?

When following a high-fiber diet, it’s recommended to include a variety of fruits and vegetables in your meals to provide the gut bacteria with the appropriate types of soluble fiber. However, not everyone tolerates all types of fiber equally well. Many types of soluble fiber are broken down quickly by the gut flora. Under certain circumstances, this can lead to the rapid production of large amounts of gas—a common cause of bloating, a feeling of fullness, and stomach pain.Slower breakdown, on the other hand, ensures better tolerance.

The following soluble dietary fibers are broken down slowly and are thereforeparticularly well toleratedeven by those with sensitive digestive systems, making them especially useful as prebiotics:

  • partially hydrolyzed guar gum (PHGG)
  • Acacia fiber
  • resistant dextrin (RS4)
  • α-Gluco-oligosaccharides

In addition, when taking dietary supplements containing soluble fiber (prebiotics), it is recommended to combine different types of soluble fiber so that all bacterial strains receive the “food” they need.

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Soluble and Insoluble Fiber—What's the Difference?

Neither soluble nor insoluble dietary fiber can be broken down by the human body’s digestive enzymes. But what exactly is the difference? Insoluble dietary fibers, such as cellulose and lignin, cannot be broken down by beneficial gut bacteria, meaning they are not prebiotic food components. However, they are just as beneficial for our gut in a different way. First and foremost, they increase stool volume, which in turn leads to improved bowel function. Since they also keep you feeling full for a long time, both soluble and insoluble dietary fiber should be included in our diet.

Insoluble fiber is found primarily in grains and legumes and should be included more often in your diet because of its beneficial effects on the gut. Some of the best high-fiber foods for this purpose are:

  • Grains
  • Legumes
  • Seeds (psyllium husks, flaxseeds)
  • Vegetables (e.g., strings on green beans)
  • Mushrooms
  • Nuts

FREQUENTLY ASKED QUESTIONS

Dietary fiber can have a positive effect on various parts of the body. These include:

  • Digestion: Insoluble fiber aids digestion by absorbing water. This facilitates bowel movements and prevents constipation. 
  • Gut Flora: Soluble fiber serves as “food” for the good bacteria in our gut. It promotes the growth and activity of beneficial gut bacteria and helps maintain a healthy balance in the gut flora.
  • Cholesterol Levels: Some types of dietary fiber, particularly soluble fiber, can bind to bile acids and be excreted along with the cholesterol they contain. This lowers cholesterol levels.
  • Feeling of fullness: Foods rich in dietary fiber contain a lot of fiber, which helps you feel full for a long time. 
  • Blood Sugar: Some types of dietary fiber can slow the absorption of sugar into the bloodstream, which can help maintain stable blood sugar levels. 
  • Cardiovascular System: Regular consumption of dietary fiber has a positive effect on many aspects of the metabolic system, including weight, blood pressure, and cholesterol levels. 

Soluble dietary fibers such as guar gum, acacia fiber, dextrin, and inulin are also known as swelling agents. They serve as the primary food source for beneficial gut bacteria and are therefore particularly valuable for gut health. Soluble dietary fibers are found mainly in:

  • various types of fruit, such as apples and citrus fruits
  • Vegetables such as carrots, artichokes, and broccoli
  • Grains such as oats, barley, and rye
  • Legumes such as lentils, beans, and peas

Soluble fiber offers many health benefits. These include:

  • Healthy and regular bowel movements
  • “Food” for the good gut bacteria
  • Support for the intestinal lining
  • positive effects on the brain (gut-brain axis)
  • Elimination of Toxins
  • increased feeling of fullness
  • Lowering Cholesterol Levels
  • Stabilization of blood sugar levels

Various types of dietary fiber are important for our gut health, including:

  • Soluble fiber: It dissolves in water and helps regulate bowel movements and make it easier to have a bowel movement.
  • Prebiotic fiber: It is a type of soluble fiber that serves as food for our beneficial gut bacteria. As a result, it promotes their growth and activity, which contributes to a healthy microbiome. 
  • Insoluble dietary fiber: It increases stool volume and speeds up its passage through the intestines. This helps prevent constipation and promotes intestinal health. 

Yes, soluble fiber is also available as a dietary supplement. It serves as “food” for the good gut bacteria and supports digestion, bowel movements, and the immune system. Pro Präbioma combines four types of soluble fiber, supplemented with calcium and zinc.

The correct term is “prebiotic fiber.” It is not digested by our enzymes, reaches the large intestine, and serves as food for beneficial bacteria there.

Both are types of soluble dietary fiber and promote the growth of beneficial gut bacteria. When broken down by bacteria, they produce short-chain fatty acids, which improve the gut environment and strengthen the intestinal lining.

Dietary fiber can be obtained from high-fiber foods such as fruits, vegetables, and whole grains. When it comes to dietary supplements, a combination of various soluble fibers is recommended, as this ensures that all gut bacteria are optimally nourished. This is put into practice, for example, in Pro Präbioma, the Probiotics Gut Cure Original, and the Probiotics Gut Cure Pur.

FACT-BASED KNOWLEDGE FOR YOUR HEALTH

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Intestines & Digestion
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