Effect of psyllium, calcium polycarbophil, and wheat bran on secretory diarrhea induced by phenolphthalein

Abstract

Background: Fiber and water-holding agents are used for the treatment of constipation. In what may appear to be a paradox, they are sometimes also used for the treatment of diarrhea; it has been proposed that they sequester water from liquid stools and/or increase the ratio of fecal solids to fecal water and thereby improve stool consistency. The purpose of the present study was to test the validity of this hypothesis in normal subjects in whom secretory diarrhea was induced by phenolphthalein.

Methods: In random sequence, 9 subjects with phenolphthalein-induced diarrhea were treated with placebo, psyllium, calcium polycarbophil, or wheat bran.

Results: Calcium polycarbophil and wheat bran had no effect on fecal consistency or on fecal viscosity. By contrast, psyllium made stools firmer and increased fecal viscosity. In a dose-response study in 6 subjects, doses of 9, 18, and 30 g of psyllium per day caused a near linear increase in fecal viscosity.

Conclusion: Psyllium, but not calcium polycarbophil or wheat bran, improves fecal consistency and viscosity in subjects with experimentally-induced secretory diarrhea.