Types of Dietary Fiber
Dietary fiber is a type of carbohydrate found primarily in plant foods that is not fully digested by human digestive enzymes.
Unlike digestible carbohydrates, much of the fiber we consume passes into the large intestine, where certain types can be fermented by intestinal microorganisms.
Fiber is commonly described in two categories.
Soluble Fiber
Soluble fiber dissolves or disperses in water, and some forms create a gel-like substance within the digestive tract.
Examples include:
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Oats
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Barley
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Beans and lentils
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Apples
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Citrus fruits
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Psyllium
Certain viscous soluble fibers can help lower LDL cholesterol and slow the absorption of glucose after meals.
Some soluble fibers are also fermented by intestinal bacteria, producing compounds that support intestinal health.
Insoluble Fiber
Insoluble fiber generally does not dissolve in water and can help increase stool bulk and support regular bowel movements.
Sources include:
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Whole-wheat products
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Wheat bran
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Nuts
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Seeds
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Vegetable skins
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Certain leafy vegetables
Most fiber-containing foods provide a combination of soluble and insoluble fibers.
The important distinction is that different fibers have different physiological properties. Their effects depend on characteristics such as viscosity, fermentability, and water-holding capacity.