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  4. What is dietary fiber?
  5. The classifications and features of dietary fiber

The surprising facts about dietary fiberThe classifications and features of dietary fiber

Broadly, dietary fiber is divided into two types, each with different characteristics: soluble fiber and insoluble fiber.

Insoluble dietary fiber

A feature of insoluble fiber is the long, rough, threadlike filaments found in vegetables and other foods.

Insoluble fiber-rich foods
In addition to grains, vegetables, and legumes, insoluble fiber is also found in the shells of shrimp and crabs.
Features of insoluble fiber
  • High water retention
    Insoluble fiber swells up as it absorbs water in the stomach and intestines, stimulating the intestine, activating peristalsis, and promoting bowel movements.
  • Fibrous, honeycombed, and spongy
    Insoluble fiber requires chewing well when eaten, helping prevent overeating, strengthening the jaw, and improving teeth alignment.
  • Fermentability
    When insoluble fiber ferments and decomposes in the large intestine, bifidobacteria and other gut flora increase, improving the intestinal environment, which has an intestinal regulation effect. Generally, insoluble fiber is less fermentable than soluble fiber.

Soluble dietary fiber

Soluble fiber can have sticky or non-sticky texture.

Soluble fiber-rich foods
Soluble fiber is found in foods such as kelp, wakame seaweed, konjac food, fruits, and taro potatoes. The raw ingredient of konjac foods dissolves in water, but solid konnyaku does not.
Features of water-soluble fiber
  • Viscosity
    Food containing soluble fiber travels through the stomach and intestines slowly because of its viscosity, reducing hunger and helping prevent overeating. It suppresses spikes in blood sugar after eating by slowing the absorption of sugar.
  • Adsorptive property
    Soluble fiber adsorbs bile acid and cholesterol, aiding their excretion from the body.
  • Fermentability
    When soluble fiber ferments and decomposes in the large intestine, bifidobacteria and other good bacterium increase, improving the intestinal environment, which has an intestinal healing effect.

Soluble fibers frequently used as a food ingredient

  • Indigestible dextrin
    Dietary fiber made from starch as a supplement that is added to foods to prevent fiber deficiency. This is the the most frequently used form of dietary fiber, is very safe and is approved for use in 'food for specified healthuse' by the Consumer Affairs Agency (Japan).
  • Polydextrose
    Dietary fiber made by mixing glucose, sorbitol and citric acid. It has the effect of increasing blood glucose levels and reducing cholesterol.
  • Barley beta glucan
    Contained in barley, an important source of dietary fiber. Has the effect of increasing blood glucose levels and reducing cholesterol.

It is widely known that dietary fiber is good for maintaining your health, but it also has a number of other benefits.