MadSci Network: Biochemistry

Re: How much of soluble fiber is digested as calories

Date: Tue Nov 23 07:46:30 1999
Posted By: Mary Hadley, Faculty, Food and Nutrition, North Dakota State University
Area of science: Biochemistry
ID: 939504344.Bc

The short answer is NONE.

Fiber is not digested or absorbed by human.It does not matter if it is soluble or insoluble fiber we get no calories from it because we do not digest or absorb it.

Now there is a little twist. All fiber ends up in the large intestine and in there we have a many many microflora (bacteria). The bacteria can ferment(Bacteria don't digest. They ferment.) some of the fiber and often produce chemicals that we can absorb. How much of the fiber is converted into chemicals that we can absorb and how much we absorb depends on the bacterial present in the gut.

One of the definitions of dietary fiber is:
Any non-starch polysaccharide that is neither digested nor absorbed.

There are other more inclusive definitions but this is the basis for deterimining what we call fiber.

By the way, fiber is not a nutrient. To be a nutrient a substance ahs to be digested and absorbed.

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