PARTICLE-SIZE OF WHEAT BRAN IN RELATION TO COLONIC FUNCTION IN RATS

Wheat bran is widely used in the treatment of constipation and may be beneficial in preventing a range of diseases including colorectal canc er: However, the results of different studies show variability in the effects of wheat bran. This could be a consequence of different brans having different ranges of particle sizes which may affect the transit time through the gastrointestinal tract. This possibility was tested using male Fisher 344 rats which have been widely used in carcinogenic ity studies The effects on transit time of supplementing the diet (a h igh fat modification of the AIN-76(TM) diet) with wheat bran fractions with particle size ranges of 212-710 mu m, 710-1000 mu m, and 1000-17 00 mu m was examined. Fractions were obtained by sieving wheat bran ob tained from a hard bread wheat (cv. Otane). Transit times were measure d using glass bends (diameter 150-170 mu m). Supplementation of the di et with each of the wheat bran fractions significantly reduced transit times (P < 0.05), but the fraction with the largest particles was the most effective. Similarly, each fraction increased the rate of excret ion of faeces (on a dry weight basis), the fraction with the largest p articles producing the greatest effect. These results are consistent w ith human studies which showed that shorter transit times resulted fro m supplementing the diet with large compared with small wheat bran. (C ) 1997 Academic Press Limited.