S J Lewis1, K W Heaton. 1. University Department of Medicine, Bristol Royal Infirmary, UK.
Abstract
OBJECTIVE: The mechanisms by which dietary fibre exerts is laxative action are not fully understood. Studies using sliced plastic tubing as a fibre substitute showed a decrease in both small and large bowel transit time. The significance of these studies is hard to interpret. We set out to compare the effects on intestinal function of wheat bran with plastic flakes similar in size and flaky shape to wheat bran (and devoid of plasticizers). DESIGN AND METHODS: Volunteers consumed coarse wheat bran then, after a washout period, plastic flakes of the same size and shape as the bran. Before and after each intervention whole-gut transit time (WGTT), defecation frequency, stool form, stool water content, stool beta-glucuronidase activity and dietary intake were assessed. RESULTS: Twenty-nine volunteers consumed a mean of 27.1 g of raw wheat bran and 24 g of plastic flakes a day. Baseline WGTT, interdefecatory intervals (IDI), stool form, weight, output, water content, and beta-glucuronidase were similar before both interventions. Both led to a decrease in mean faecal beta-glucuronidase activity, median WGTT (bran 25.8%, plastic 28.6%) and IDI (bran 23.3% plastic 25.0%). Both also increased stool form score (bran 28.6%, plastic 21.2%) and stool output (bran 67.1%, plastic 79.0%). Stool water content only rose with wheat bran (72%-75%, P = 0.014). CONCLUSION: Overall, plastic 'pseudobran' was as effective at altering colonic function as wheat bran at a similar dosage but with fewer particles. The mechanism is not by increased faecal water. Reduction in enzyme activity with plastic flakes suggests that the plastic led to qualitative and, probably, beneficial changes in the bacterial flora or their metabolic processes. The concept of roughage deserves to be revived.
OBJECTIVE: The mechanisms by which dietary fibre exerts is laxative action are not fully understood. Studies using sliced plastic tubing as a fibre substitute showed a decrease in both small and large bowel transit time. The significance of these studies is hard to interpret. We set out to compare the effects on intestinal function of wheat bran with plastic flakes similar in size and flaky shape to wheat bran (and devoid of plasticizers). DESIGN AND METHODS: Volunteers consumed coarse wheat bran then, after a washout period, plastic flakes of the same size and shape as the bran. Before and after each intervention whole-gut transit time (WGTT), defecation frequency, stool form, stool water content, stool beta-glucuronidase activity and dietary intake were assessed. RESULTS: Twenty-nine volunteers consumed a mean of 27.1 g of raw wheat bran and 24 g of plastic flakes a day. Baseline WGTT, interdefecatory intervals (IDI), stool form, weight, output, water content, and beta-glucuronidase were similar before both interventions. Both led to a decrease in mean faecal beta-glucuronidase activity, median WGTT (bran 25.8%, plastic 28.6%) and IDI (bran 23.3% plastic 25.0%). Both also increased stool form score (bran 28.6%, plastic 21.2%) and stool output (bran 67.1%, plastic 79.0%). Stool water content only rose with wheat bran (72%-75%, P = 0.014). CONCLUSION: Overall, plastic 'pseudobran' was as effective at altering colonic function as wheat bran at a similar dosage but with fewer particles. The mechanism is not by increased faecal water. Reduction in enzyme activity with plastic flakes suggests that the plastic led to qualitative and, probably, beneficial changes in the bacterial flora or their metabolic processes. The concept of roughage deserves to be revived.