The effect on colonic function of adding wheat fiber for 3 weeks to the metabolically-controlled diets of six healthy volunteers has been studied. Increasing dietary fiber intake from 17 to 45 g/day increased fecal weight from 79 +/- 6.6 g/day to 228 +/- 29.9 g/day and shortened mean transit time, measured by a continuous marker method, from 57.8 +/- 8.3 hr to 40.3 +/- 8.9 hr. The increase in fecal weight was largely due to water. Fiber caused a dilution of fecal marker and an increase in fecal fat, nitrogen, and calcium output. Fecal sodium, potassium, and chloride showed only small changes but volatile fatty acid output increased significantly without concentrations changing. Fecal bile acid output increased from 199 +/- 46 mg/day to 279 +/- 46 mg/day. These changes are discussed in light of current views of the role of dietary fiber in protecting against colon cancer.

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SUMMARY Three-day faecal collections were obtained from 87 patients with a variety of gastroenterological diagnoses and 12 control subjects while consuming normal diets. Faecal weight, total fatty acids, and the proportion of hydroxystearic (OHSA) acid were measured. All patients had some easily detectable hydroxystearic acid. It was found that in general the percentage of OHSA in the faecal fatty acids increased with increasing fat output. Thus most patients excreting less than 20 g of fat per day had less than 5 % OHSA while those with greater steatorrhoea had levels of 6 to 23 %. Exceptions were patients with mild steatorrhoea with ileal disease, ileal resections, or small intestinal bacterial colonization, who had more than 5 % OHSA whilst patients with colonic resection had much lower levels of OHSA than otherwise found. It is impossible to determine whether OHSA had a specific cathartic action from this study since the data implicated total fatty acids to the same extent.

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