[Dietary fiber. Effect on colon carcinogenesis]

The etiopathogenesis of colon carcinogenesis is supposed to be a two-step process consisting of initiation and promotion. In human nutrition the range of xenobiotics acting possibly as initiators occurs mostly in very low concentrations. Therefore, performing a one-factorial consideration they are not claimed seriously to account for initiation. On the contrary, it can be taken for granted that bile acids exert promoting effects in connection with colon carcinogenesis. All factors influencing the promoting effect of bile acids are able to do so probably due to a decrease of pH and as a result the shift of the two bile acid fractions in favour of the soluble fraction, and/or due to the intensification of shift of bile acid metabolism (7-alpha-dehydroxylase). These processes are indirectly influenced to a large extent by the lipid content of food as a result of cholegenesis induction. The "protective Effect" of dietary fibre in colon carcinogenesis (reduced number of tumour carriers, and/or number of tumors per animal) cannot been interpreted as such. Only a delayed promotion phase could been proven. It can be reached only by plant products (bran, lupin), but not by dietary fibre in general.