Arabinoxylan fiber from a by-product of wheat flour processing behaves physiologically like a soluble, fermentable fiber in the large bowel of rats

Arabinoxylan is a major dietary fiber component of many cereals. Its physio logical effects in the colon are largely unknown. This study examined the e ffects of an arabinoxylan-rich fiber (AX) extracted from a by-product of wh eat flour processing in the rat colon compared with well-characterized solu ble/rapidly fermentable and insoluble/slowly fermentable fibers. Rats were fed diets containing no fiber (NF) or 100 g/kg of total dietary fiber from AX, guar gum (GG) or wheat bran ONE) for 4 wk. Cecal mass and short-chain f atty acid (SCFA) pool were significantly higher while pH was significantly lower in the fiber-supplemented groups, particularly in the AX and GG group s. The pattern of SCFA production in the cecum was altered; AX fiber was a good source for acetate while GG and WE favored propionate and butyrate pro duction, respectively. Fecal output was 7-, 6- and 5-fold higher, respectiv ely, in the AX, GG and WE than in the NF groups (P < 0.01). All epithelial proliferation indices (crypt column height, number of mitotic cells/crypt c olumn and mitotic index) differed significantly across the groups in a desc ending order of AX > GG > WE > NF. Distal mucosal dipeptidyl peptidase IV a ctivities, which indicate cell differentiation status, were significantly l ower in fiber-supplemented groups than in the NF groups. Distal mucosal alk aline phosphatase activities, induced as a response to injury or stress, we re significantly higher for the AX and GG groups than for the NF or WE grou ps (P < 0.001). These results indicate that AX fiber behaves like a rapidly fermentable, soluble fiber in the rat colon.