Microfibril
wheat bran (MFW), a processed
dietary fiber prepared by milling of coarse
wheat bran (WB), is softer and has a more pleasant taste than WB. In this study, we examined the inhibitory effect of MFW on
azoxymethane (AOM)-induced colon
carcinogenesis in female CF1 mice and compared its effect with that of WB and
cellulose (CL). The mice were fed a modified AIN 76 A diet supplemented with either MFW, WB, or CL at a final concentration of 20% (w/w). Six weekly s.c.
injections of AOM (10 mg/kg
body weight) were administered per mouse commencing 1 week after the start of the feeding period. Control mice were injected with saline only. Thirty-three weeks after the initial injection, the mice were sacrificed, examined for
tumors, and the cecal contents were analyzed to determine the moisture content and the concentrations of
short-chain fatty acids (SCFA). The average number of total
tumors per mouse in the MFW (2.9 +/- 0.6, P = 0.017) and WB (5.3 +/- 1.3, P = 0.373) diet groups was lower than that of the CL diet group (7.5 +/- 1.3), though there was no significant difference in
tumor incidence (94.7%, 90.0% and 94.7%, respectively) between the groups. More than 90% of the
tumors in each group were
adenocarcinomas. The incidence of
adenoma and that of
carcinoma in situ in the MFW diet group (5.3% and 0%, respectively) were also lower than those in the CL diet group (26.3 and 26.3%, respectively; P = 0.180 and P = 0.046, respectively). Analysis of the cecal contents revealed a significantly higher moisture content and significantly higher concentrations of SCFA,
butyrate in particular, in the MFW and WB diet groups. The results of this study indicate that the source and texture of
dietary fiber can influence
tumor development in CF1 mice, and more specifically that MFW is a promising and useful dietary supplement with properties serving to protect against the development of
colon cancer.