11/13/2001

Chow Line: Fiber is a carb, but it's not absorbed (for 11/25/01)

Writer:

Martha Filipic
filipic.3@osu.edu
(614)292-9833

Source:

Sharron Coplin

I read on one website that the body absorbs all carbohydrates within five minutes. On another site, I saw fiber isn't absorbed at all. Which is right?

First, some background. Fiber is mainly a collection of complex carbohydrates, the basis of which is the glucose molecule. Glucose molecules hook up with other types of molecules, such as fructose, and can be consumed in the form of sugar, starch or fiber.

However, molecules that form fiber are strung together differently than those that form starch or sugar. Because of that different configuration, fiber is not digested or used by the body for energy. We simply don't have the enzymes necessary to break down and absorb fiber-type carbohydrates.

That's why high-fiber foods tend to fill you up without adding calories to your diet. High-fiber foods add volume, and usually lots of fluid and a greater proportion of vitamins and minerals, than low- or no-fiber foods.

Even though fiber is a type of carbohydrate, people who "count carbs" usually don't include fiber. Fiber is included in the overall carbohydrate content listed on food labels, but you can easily tell how much of those carbohydrates are fiber because fiber is listed as a sub-category directly beneath the carbohydrate listing.

One more thing: Both sugars and starches can take longer than five minutes to be absorbed by the body. Starch may get converted to the smaller glucose units almost that quickly -- just by chewing a cracker, for example, your saliva helps break down starches to sugars. But carbohydrates also contain other sugars (such as fructose and galactose) that are absorbed and eventually metabolized to glucose, and that takes longer than five minutes. It might be done in three hours.

Health experts recommend consuming 20 to 30 grams of fiber a day. High-fiber foods include beans, whole grains, fruits, vegetables, nuts and seeds.

Chow Line is a service of The Ohio State University. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH 43210-1044, or filipic.3@osu.edu.

Editor:
This column was reviewed by Sharron Coplin, registered dietitian and Ohio State University Extension associate in the College of Human Ecology.