Comparison of the effects on colonic function caused by feeding rice bran and wheat bran

A study was designed to investigate the effects of a new fibre source, rice bran, on colonic function, and to compare it with wheat bran. The diet of eight normal male volunteers was supplemented with similar amounts of indigestible residue from rice (17.1 g/d) and wheat bran (15.0 g/d) for periods of 10 d each. During the last 7 d of each of these periods, and also of a 10-d control period when no supplement was taken, the volunteers collected their stools into plastic bags. This allowed calculation of stool mass and frequency, and gastrointestinal transit time by a continuous radio-opaque marker technique. Rice bran increased the mass of faeces produced and the stool frequency by more than the wheat bran, but both had a similar accelerating effect on the transit time. The mechanism of the efficient stool bulking caused by the rice bran may be due to a high content of retrograded starch.