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%
dietary fiber. Gastrointestinal
tumors were induced with
dimethylhydrazine given weekly for five weeks at 15 mg/kg body wt by
subcutaneous injection, commencing four weeks after rats were established on the experimental diets. At 32 weeks of age, rats were killed and
tumors assessed. The insoluble
dietary fiber-rich source from barley (spent barley grain, SBG) was significantly more effective at preventing induced
tumors than soluble fiber-rich commercial barley bran. There were no significant differences among the results for the other three fiber sources, which were intermediate in their influence. Both incidence of rats affected and
tumor mass index were reduced, the latter significantly, when 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 different from
wheat bran at this stage. Pure
cellulose and outer-layer barley bran were, by comparison, only moderately effective in
cancer prevention. SBG, like
wheat bran, is a good source of
cellulose and
hemicellulose. It is also a good source of
proteins, polyphenolics,
fatty acids (including alpha-linolenic),
vitamin E, and minerals. Further research is needed to clarify the relevance of these other factors to the differences observed.(ABSTRACT TRUNCATED AT 250 WORDS)