A COMPARATIVE-STUDY OF THE INFLUENCE OF DIFFERING BARLEY BRANS ON DMH-INDUCED INTESTINAL TUMORS IN MALE SPRAGUE-DAWLEY RATS

The influence of barley brans on the incidence and burden of intestina l rumours in rats induced by 1,2-dimethylhydrazine (DMH) was studied i n a 7 month feeding experiment. The basic diet was American Institute of Nutrition (AIN) 76 modified by adjustment to 20% fat and 40% starch ; brans were added so as to supply 5% dietary fibre. The barley brans studied were commercial barley bran (BEI; 13.0% dietary fibre) from th e aleurone/subaleurone layer, outerlayer barley bran (BB2) including t he germ (25.5% dietary fibre) and spent barley grain bran (SBG; a by-p roduct of the brewery and including the hull; 47.7% dietary fibre). Th ey were compared with wheat bran (WB; 44% dietary fibre) and cellulose (or control; 98% dietary fibre). Commercial barley bran and wheat bra n were most effective in reducing tumour incidence and burden. The inc idence of rumours fell significantly from 70% (BB2) and 50% (SBG) to 1 0% (BB1) and 20% (WB) and tumour burden and tumour mass index (TMI) we re also reduced by similar orders of magnitude. There were significant ly higher short chain fatty acid (SCFA) concentrations in WB- and BB1- fed rat faecal pellets relative to cellulose- and BB2-fed rat faeces; butyrate, in particular, was affected. Regression analysis of butyrate against tumour incidence showed a trend (1 = -0.898; P = 0.055), bur. the concentration of butyrate alone could not account for the reducti on in tumour incidence observed. In a second experiment, when two bran s (BB1 and SBG) were introduced after DMH dosing, there were higher in cidences and burdens of rumours, indicating that protection by such br ans was not as effective under these circumstances. Commercially avail able barley bran and wheat bran appear to significantly reduce tumour incidence and burden in this model relative to other brans, influencin g both the initiatory as well as promotional stages of chemically indu ced carcinogenesis.