Degradation of Dietary Fiber by Faecal Bacteria and Potential Physiological Effects (Report‪)‬

INTRODUCTION The risk of colon and rectal cancer has been associated with the intakes of vegetables and other plant foods rich in fiber [1, 2]. The benefits of fiber against colon cancer were closely associated to both the fermentative and the non-fermentative processes, where the poorly fermentable fibers were regarded to be more influential [3]. Dietary fibers are viscous, indigestible polysaccharides derived from plant foods which are not degraded by enzymes of the alimentary tract; therefore, they reach the colon undegraded and serve as potential fermentation substrates for the colon microorganisms, particularly bacteria [3, 4]. The nature of the colonic bacterial flora, the transit time through the colon and the physical and chemical composition of the fiber determine the extent of the fiber breakdown by bacterial enzymes. Fiber digestion occurs almost exclusively in the colon: 29-82% of ingested cellulose, 56-87% of hemicellulose and 90% of pectin are lost during passage through the colon [5]. Lignin, by virtue of its polymeric cross-linked structure, is resistant to bacterial digestion and is virtually completely recovered in the stool. Degradation of fiber results in the production of compounds such as methane, carbon dioxide, hydrogen, water and short chain fatty acids [3, 6]. The production of these compounds is catalyzed by enzymes produced in response to the degradation of fiber [6]. The dietary fiber composition and the degree of degradation by gut microflora of most food consumed in Nigeria have not been reported. In this study, Ex Manihot esculenta (also called "gari"), Musa paradisiaca (matured green plantain), Gnetum africana leaves and Telfaria occidentalis leaves were analysed for dietary fiber content and bacterial degradation. Gari when made into a semi-solid meal by stirring with boiling water is usually eaten with vegetable soup. It is the main staple food of people in the Eastern States of Nigeria. Matured green plantain when boiled or cooked into porridge form is known for its ability to hold loose bowel. It is also regarded by some consumers to be a good recipe for diabetic patients.