EFFECT OF CEREAL FIBER SOURCE AND PROCESSING ON RECTAL EPITHELIAL-CELL PROLIFERATION

Background-Low fat and wheat interventions significantly reduced growt h of small to large adenomas and modestly suppressed rectal epithelial cell proliferation in the Australian Polyp Prevention Project. Aim-To study the effect of unprocessed wheat bran, unprocessed oat bran and processed wheat bran (Kellogg's All Bran) on rectal epithelial cell pr oliferation. Patients-Twenty subjects with recent adenomas and a high fat background diet were recruited. Methods-Rectal biopsy specimens we re taken at entry and at the end of three six-week periods of oat bran (64 g/day), wheat bran (25 g/day) and All Bran (38 g/day), all in ass ociation with a diet <25% energy as fat, in a randomised cross-over tr ial. Each of the bran supplements had a total of 11 g dietary fibre. T he biopsy specimens were fixed in methacarn and stained immunohistoche mically for presence of the proliferating cell nuclear antigen (PCNA). The kinetics used to measure proliferation were labelling index, whol e distribution of labelled cells, and labelled cells in the top two-fi fths of crypts using analysis of variance. Results-There were no signi ficant differences in mean labelling indexes between or in the percent age of in the top two-fifths (p=0.59), but activity in the top two-fif ths of crypts was lowest with wheat bran. The mean (SD) labelling inde xes were 2.23 (0.11)% for control, 2.13 (0.08)% for wheat bran, 2.19 ( 0.09)% for oat bran, and 2.12 (0.08)% for All Bran. The proportion in the top two-fifths of the crypts was 2.6 (0.6)% for control, 2.15 (0.5 )% for wheat bran, 3.3 (0.9)% for oat bran, and 3.1 (0.9)% for All Bra n. On analysis of whole distribution, there was no significant overall effect of diets but there was a difference between subjects. Analysis including total fibre intake also did not identify effects on prolife ration. Conclusion-In this study of high risk subjects with initial hi gh fat diets, dietary fibre in association with a low fat diet had no effect on rectal epithelial cell proliferation, although wheat bran ha d the greatest effect on percentage of labelled cells in the top two-f ifths of crypts.