Effects of Dietary Cellulose, Psyllium Husk and Cholesterol Level on Fecal and Colonic Microbial Metabolism in Monkeys

Abstract

The effect of long-term feeding of dietary fiber and two levels of cholesterol on monkey colonic microbial metabolism was studied. Three groups of African green monkeys were fed for 3.5 yr purified diets containing 9.7% cellulose or psyllium husk and 0.8 mg cholesterol per kcal or 9.7% cellulose and 0.1 mg cholesterol per kcal. Total viable anaerobe and aerobe counts, microbial beta-glucuronidase activity, volatile fatty acid and ammonia nitrogen concentrations, dry matter and pH were determined in fecal and colonic samples. Compared to cellulose, psyllium husk feeding decreased (P less than 0.05) percentage dry matter, beta-glucuronidase (EC 3.2.1.31) activity and pH, and increased (P less than 0.05) ammonia nitrogen and volatile fatty acid output in feces and in colon contents. In all groups, colonic beta-glucuronidase activity was greater (P less than 0.05) than in fecal samples. Microbial beta-glucuronidase activity, pH or percentage dry matter in the ascending colon was not different from that in the transcending or descending segments. The ratio of anaerobic to aerobic bacteria was lower in colon contents from monkeys fed psyllium husk compared to those fed cellulose. Total viable bacterial counts were lower in monkeys fed low cholesterol compared to high cholesterol diets. The results suggest that chronic intake of dietary psyllium husk resulted in greater colonic microbial metabolism compared to cellulose feeding.