Irritable Bowel Syndrome Message Boards | Re: Fiber and digestion?

Digestion takes place through out the gut. The answer to your question depends on where in the gut you are talking about and which type of fiber you are talking about.

Here is are some quotes from IBS research articles (references below) that describes the role of soluble and insoluble fiber in the gut.

"Traditionally, fiber is divided into soluble (gums, pectins, and ispaghula) and insoluble (cellulose, hemicellulose, lignins, and bran) forms. The soluble forms delay gastric emptying, small intestinal transit, and nutrient absorption. Insoluble fiber is less susceptible to bacterial degradation and tends to accelerate transit through the colon more effectively than soluble forms. Overall, increased dietary fiber intake results in heavier, softer stools with reduced colonic and whole gut transit times."

"Soluble fibers appear to slow transit [in small intestine] and stimulate growth of the flora and by the affect on short-chain fatty acid production affect cholesterol metabolism."

"Pectin [a soluble fiber] has reported to exert a variety of effects on the gastrointestinal tract such as: (1) maintaining the morphology and structure of the intestinal villi, (2) increasing lipase activity,(3) delaying gastric empting time, (4) increasing intestinal transit time and (5) increasing SCFAs generation."

In summary soluble fiber slows emptying of the stomach and small intestine transit time while insoluble fiber tends to decrease transit time in the colon.

Reference
Matthew, J. V. L., & Whorwell, P. J. (1998). Bran: May Irritate Irritable Bowel . Nutrition, 14(5), 470

Park, J., & Floch, M. H. (2007). Prebiotics, Probiotics, and Dietary Fiber in Gastrointestinal Disease Gastroenterology Clinics of North America Nutrition in Gastrointestinal Illness, 36(1), 47-63

Andoh, A., Tsujikawa, T., & Fujiyama, Y. (2003). Role of Dietary Fiber and Short-Chain Fatty Acids in the Colon. . Current Pharmaceutical Design, 9(4), 347-358

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