Dietary fibre and the mouse colon: its influence on luminal pH, reducing activity and bile acid binding.

Female, Swiss mice were fed semi-synthetic diets for 33 days. The diets were fibre-free (FF) or supplemented with corn bran (CB) 12%, wheat bran (WB) 12%, alfalfa (AL) 12%, pectin (P) 6%, cellulose (CL) 6%, or lignin (LG) 6%. Fibre caused little hyperplasia of the colon mucosa. The number of cells per crypt was increased 9-13% and the crypt column length by 14-19% in the CL, AL and LG groups. CB caused rather less hyperplasia, WB less again and P caused none. The colon mucosal DNA content was approximately 5-10% lower in mice given supplemental fibre. The pH of the contents of the distal colon was apparently unaffected by fibre. Measurement of a non-specific, non-enzymic reducing activity indicated that activity was doubled by AL and LG, lowered 41% by CB but little changed by WB, CL and P. The deoxycholate binding capacity of the colon contents was increased 3--4-fold by LG, whereas the other fibre sources were without appreciable effect. This high binding capacity by LG was also seen in the material used for diet preparation. Analyses of the contents of the caecum and of the remaining colon indicated that as food residue passes from the caecum to the remaining colon little change in binding capacity occurs.