THE POTENTIAL OF AN INSOLUBLE DIETARY FIBER-RICH SOURCE FROM BARLEY TO PROTECT FROM DMH-INDUCED INTESTINAL TUMORS IN RATS

The influence of soluble and insoluble dietary fiber supplements from barley and wheat on colon cancer risk was assessed using male Sprague- Dawley rats from four weeks of age on a semipurified (AIN76A) rat diet modified to contain 20% fat of mixed animal and plant origin and 5% d ietary fiber. Gastrointestinal tumors were induced with dimethylhydraz ine given weekly for five weeks at 15 mg/kg body wt by subcutaneous in jection, commencing four weeks after rats were established on the expe rimental diets. At 32 weeks of age, rats were killed and tumors assess ed The insoluble dietary fiber-rich source from barley (spent barley g rain, SBG) was significantly more effective at preventing induced tumo rs than soluble fiber-rich commercial barley bran. There were no signi ficant differences among the results for the other three fiber sources , which were intermediate in their influence. Both incidence of rats a ffected and tumor mass index were reduced, the latter significantly, w hen SBG was compared with commercial barley bran. SBG also produced a significant reduction in plasma cholesterol concentration (down 17%, p < 0.05) relative to wheat bran, but commercial barley bran was not di fferent from wheat bran at this stage. Pure cellulose and outer-layer barley bran were, by comparison, only moderately effective in cancer p revention. SBG, like wheat bran, is a good source of cellulose and hem icellulose. It is also a good source of proteins, polyphenolics, fatty acids (including alpha-linolenic), vitamin E, and minerals. Further r esearch is needed to clarify the relevance of these other factors to t he differences observed SBG as a dietary fiber source appears to be ve ry effective in protecting rats from dimethylhydyazine-induced intesti nal cancer.