Ameliorative effects of konjac glucomannan on human faecal ß-glucuronidase activity, secondary bile acid levels and faecal water toxicity towards Caco-2 cells.

Konjac glucomannan (KGM) has been shown to increase human colon microbial ecology and reduce faecal toxicity in mice. The main goal of the present study was to assess the effects of a KGM supplement into a low-fibre diet on precancerous markers of colon cancer in a double-blind, placebo- and diet-controlled study. Adult volunteers consumed defined diets supplemented with konjac (4·5 g/d) or placebo (maize starch) for 4 weeks. Stools collected before and at the end of the supplementation were analysed for ß-glucosidase, ß-galactosidase and ß-glucuronidase activities, microflora and bile acids. Faecal water was co-incubated with Caco-2 cells, a model of human colonocytes, to determine the cytotoxicity and DNA-damaging effect as assessed by the comet assay. The results indicated that the KGM supplement significantly decreased faecal ß-glucuronidase activity by 25·6 (se 7·8) % and faecal secondary bile acid level by 42·4 (se 11·8) %. In contrast, consuming the defined diet supplemented with placebo for 4 weeks did not improve these determinants. The KGM-supplemented diet, but not the placebo diet, significantly increased the survival rate (%) of Caco-2 cells co-incubated with faecal water for 1 and 3 h, respectively. In addition, KGM significantly reduced the DNA damage induced by the faecal water alone or in combination with H2O2. The faecal bifidobacteria and lactobacilli levels increased only with the KGM-supplemented diet. Therefore, we conclude that supplementation of KGM into a low-fibre diet improved the faecal microbial ecology and metabolites, which may contribute to the reduced toxicity of faecal water and precancerous risk factors of human colon cancer.

Supplementation of konjac glucomannan into a low-fiber Chinese diet promoted bowel movement and improved colonic ecology in constipated adults: a placebo-controlled, diet-controlled trial.

OBJECTIVES: This diet-controlled study was designed to examine effects of konjac glucomannan (KGM) supplement on the bowel habits and colonic ecology in 7 constipated subjects. In addition, the mechanisms by which KGM modulated the bowel habit were explored. METHODS: Seven constipated subjects who passed bowel movement less than once a day participated in this diet-controlled linear study that consisted of a 21-d placebo period, a 7-d adaptation period, and a 21-d KGM-supplemented (1.5 g, tid) period. The large bowel response and fecal characteristics were recorded daily. Stools were collected individually on days 15-21 of placebo and KGM periods for analyses of colonic ecology indices such as fecal microflora, pH and short chain fatty acid content. Fecal component was determined to illustrate the fermentation of KGM. RESULTS: KGM supplement slightly but significantly increased the weekly defecation frequency from 4.1 +/- 0.6 to 5.3 +/- 0.6 and slightly eased the bowel movement. The fecal wet weight (g/d) and percent moisture were not significantly altered with the fiber supplement. However, the dry fecal weight (g/d) was increased mainly in the soluble mass. KGM supplement increased the fecal concentration (log counts/g wet feces) of lactobacilli, and the daily output (log counts/d) of bifidobacteria, lactobacilli and total bacteria in this diet-controlled study. In addition, fermentation of KGM resulted in greater fecal acetate, propionate and i-butyrate concentrations and lower fecal pH. CONCLUSION: The modest dose of KGM supplement promoted bowel movement by 30% and improved colonic ecology in constipated adults.

Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults.

OBJECTIVE: Konjac glucomannan (KGM) has been shown to relieve constipation, which could be associated with increased stool bulk and improved colonic ecology. METHODS: This placebo-controlled study consisted of a 21-d placebo period, a 7-d adaptation period when volunteers consumed KGM progressively, and a 21-d KGM-supplemented period (1.5 g/meal, 4.5 g/d). Eight healthy adults consumed 7-d cycle menus of typical low-fiber Chinese food throughout the study. The gastrointestinal response was monitored daily. Stools were fully collected on days 15 to 21 of placebo and KGM periods to determine the fecal mass, components, microflora, and short-chain fatty acid contents. RESULTS: The KGM supplement significantly increased the mean defecation frequency (number/day), wet stool weight, and dry stool weight (g/d) by approximately 27.0% (P < 0.05), 30.2% (P < 0.05), and 21.7% (P < 0.05), respectively. The dry fecal mass increased mainly in the plant and soluble material, whereas bacterial mass tended to increase from 12.9 +/- 1.6 to 13.6 +/- 2.7 g/d (P > 0.05). However, KGM significantly promoted the fecal concentrations (log counts/g wet feces) of lactobacilli (P < 0.05) and total bacteria (P < 0.05), and promoted the daily output (log counts per day) of bifidobacteria (P < 0.05), lactobacilli (P < 0.05), and total bacteria (P < 0.05) as evaluated by the fluorescence in situ hybridization method. KGM supplement also promoted colonic fermentation as shown in the decreased fecal pH (P < 0.05) and increased fecal short-chain fatty acid concentrations (P < 0.05). CONCLUSION: Supplementation of KGM into a low-fiber diet promoted the defecation frequency in healthy adults, possibly by increasing the stool bulk, thus promoting the growth of lactic acid bacteria and colonic fermentation.