Effects of a high cholesterol (HC) diet and HC diet supplemented with polydextrose on fecal flora, fecal bacterial enzyme activity and fecal putrefactive products in eight healthy volunteers were studied. They were fed a low cholesterol (LC) diet, HC diet, HC diet supplemented with polydextrose (15 g/day) (HCP) at 2-week intervals consecutively for 6 weeks. Polydextrose supplementation increased fecal weight and decreased fecal pH and the stool concentration of indole, p-cresol, iso-valeric acid and iso-butyric acid. A significant reduction of Clostridium in the feces was also observed during the HCP diet period. The frequency of occurrence and number of Clostridium perfringens in the feces were lower for the HCP diet than for the HC diet. Epidemiologic and experimental studies indicate that geographic, urbanrural, and socioeconomic differences exist in the incidence of colon and rectal cancer (4,8,18) and that dietary factors, particularly a high fat intake and a relatively low intake of certain types of dietary fiber, play important roles in their etiology (2,26,31,32). Carcinogens or cocarcinogens are produced in the gut by bacterial action on dietary components or on secretions produced in response to the diet (14). Studies comparing feces of subjects from Scotland, England and the United States (high-risk area for large bowel cancer) to subjects from India, Japan, 53

Polyphenols are plant derived compounds that exert many beneficial health effects to the human host. However, associated health benefits of dietary polyphenol are highly dependent on their intestinal metabolism, bioavailability, and absorption. Bifidobacteria, which represent the key members of gut microbiota, have been suggested to promote gut microbial homeostasis and may be involved in the metabolism of polyphenols. In this study, the capabilities of thirteen Bifidobacterium strains in hydrolysing polyphenol glycosides were evaluated. Among the tested strains, Bifidobacterium breve MCC1274 was found to possess the highest β-glucosidase activity and strong capability to convert daidzin and trans-polydatin to their aglycones; while kinetic analysis revealed that B. breve MCC1274 hydrolysed more than 50% of daidzin and trans-polydatin at less than 3 h of incubation. Further investigation using rats with an antibiotics-disturbed microbiome revealed that following the ingestion of daidzin glycoside, oral administration of B. breve MCC1274 significantly enhanced the plasma concentration of daidzein in rats pre-treated with antibiotics as compared to antibiotics-pre-treated control and non-treated control groups. The relative abundance of Actinobacteria and the total numbers of B. breve were also significantly higher in antibiotics-pre-treated rats administered with B. breve MCC1274 than that of the control groups. These findings suggest that B. breve MCC1274 is effective in enhancing the bioavailability of daidzein in the gut under dysbiosis conditions and may potentially improve intestinal absorption of isoflavones and promote human health.

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