Effects of high-fiber diet on fecal blood content (HemoQuant assay) in healthy subjects.

Consumption of high-fiber diets has been recommended prior to fecal blood testing to increase bleeding from polyps, cancer, and other lesions associated with mucosal erosion in the gastrointestinal tract. The effect of a high-fiber diet on fecal hemoglobin loss was examined in 17 healthy subjects during two dietary periods: (1) self-selected diet, (2) same diet plus 24 g/day dietary fiber (Fiber One Cereal). Five-day fecal composites were weighed and homogenized, and hemoglobin concentration was determined by the HemoQuant test. Average daily fecal weight increased from 145 +/- 90 g to 281 +/- 91 g (P = 0.0001), fecal hemoglobin concentrations decreased from 0.98 +/- 0.48 to 0.48 +/- 0.28 mg/g (P = 0.0001), while daily fecal hemoglobin contents were similar (P = 0.39) for self-selected and added-fiber diets, respectively. In these healthy individuals, a high-fiber diet had no effect on mucosal bleeding, but the increased fecal weight significantly lowered fecal hemoglobin concentration. Clinical implications are considered.