ABSTRACT
Objective: To evaluate the effect of dietary fiber and phytic acid inositol hexaphosphate (IP6 or Insp6) on 1,2-dimethylhydrazine(DMH) induced colorectal carcinogenesis in Wistar rats. Methods: 86 four-week-old male Wistar rats were divided randomly into 6 groups and fed with either basal fiber free diet or the basal diet supplemented with 10% pectin, 10% cellulose, 2% Na-InsP6 supplemented water, 10% pectin in combination with 2% Na-InsP6 supplemented water, 10% cellulose in combination with 2% Na-InsP6 supplemented water. After four weeks, the rats were given a weekly injection of DMH (20mg/kg bw) for 20 weeks. The rats were killed after 26 weeks. The number of total macroscopically visible neoplasms was counted and the volume of individual neoplasmas was calculated. Proliferation cell nuclear antigen (PCNA) was analyzed. Results: There was no significant difference between the treatment group and the control group in the incidence of tumors. InsP6 significantly reduced the number of tumors in rats and tumor volume. Pectin and Pectin+InsP6 significantly increased the number of tumors in rats. The expression of proliferation marker PCNA was significantly down-regulated by InsP6 and significantly increased by pectin. Conclusion: A treatment regimen of 2% Na-InsP6 in drinking water was effective in significantly reducing the risk of colorectal cancer in Wistar rats. Diet supplemented with pectin could increase the risk of colorectal cancer.