Abstract Objectives To evaluate the effect of consumption of yacon flour, kefir and the association between them on colon cancer induced by 1,2-dimethylhydrazine (DMH) in male Wistar rats, SCFA production, fecal pH and intestinal permeability. Methods The study was conducted with 60 adult Wistar rats divided into 5 groups. For 5 weeks, groups T, Y, K and YK received 1,2-dimethylhydrazine (DMH) to induce colon cancer. After 5 weeks of DMH administration, animals in groups C and T received the standard diet, group Y received a diet with yacon flour with 5% FOS, group K received 1mL /day of kefir and the YK group received a diet with yacon and kefir, for 15 weeks. After euthanasia, intestinal lesions, intraluminal pH, short-chain fatty acids (SCFA) and intestinal permeability were analyzed. Results An increase in macroscopic lesions was observed in groups K (58%) and YK (42%) and a reduction of 5% in group Y, compared to group T. In addition, an increase in neoplastic changes was observed in all groups compared to group T: Y (33%), K (67%) and YK (78%). There was no significant difference in the concentrations of acetate and proprionate, pH, lactulose and mannitol between groups, and butyrate was not found in the samples. Conclusions The consumption of yacon flour, kefir and their association did not influence intestinal physiology and promoted the worsening of the development of colon carcinogenesis in rats. Funding Sources FAPES - Fundação de Amparo à Pesquisa e Inovação do Espírito Santo CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico