The effect of synbiotics on colon carcinogenesis in rats

Evidence indicates that consumption of probiotic microorganisms such as bif idobacteria reduces the risk of colon cancer in animal models. Feeding cert ain fructans such as oligofructose and inulin, which are thought to selecti vely increase the growth of intestinal bifidobacteria (i.e., a prebiotic ef fect), also has been shown to reduce colon cancer risk, The objective of ou r study was twofold, i.e., to determine whether the combination of bifidoba cteria and oligofructose would,have an additive effect (i.e., synbiotic) in reducing colon cancer risk in rats, and to determine whether other oligosa ccharides would also be effective as part of a synbiotic combination. The d evelopment of colonic preneoplastic lesions (aberrant crypts) was used as a n index of colon cancer risk. In one series of experiments, rats were given the carcinogen 1,2-dimethylhydrazine (DMH) and administered one of the fol lowing treatments: skim milk (control), bifidobacteria (bifido), oligofruct ose (OF) or bifido + OF. Neither bifido nor OF alone significantly reduced aberrant crypt number. Bifido + OF reduced aberrant crypt number in five of six experiments, although the reduction was significant in only one. Howev er, a paired comparison of the six experiments indicated a significant over all reduction in aberrant crypts by bifido + OF (P = 0.039). Soybean oligos accharide (SBO) and wheat bran oligosaccharide (WBO) were also fed in combi nation with bifidobacteria. In two other experiments, SBO did not alter the number of aberrant crypts compared with the control, whereas WBO reduced a berrant crypt number in one experiment but not in another. Of OF, SBO and W BO, only SBO reduced the colonic mucosa proliferation compared with the con trol. These results suggest that the combination of bifidobacteria and olig ofructose reduces colon cancer risk in carcinogen-treated rats, but the eff ect of other oligosaccharides is uncertain.