Much attention has been focused on flavonoids because of their beneficial effects on human health. Flavonoids are the most abundant dietary polyphenols. Quercetin is one of the major flavonoids and is contained in many foods. Soybean and soy foods are rich sources of isoflavones. Recent research has shown that they are beneficial to human health. The two major sites of flavonoid metabolism are the liver and the intestinal flora. Intestinal flora play an important role in the absorption and metabolism of flavonoids. Many of the flavonols including quercetin occur in food in the form of Oglycosides, with D-glucose as the most common sugar residue. With respect to the bioavailability of flavonoid glycosides, intestinal flora are known to have an important role in hydrolysis. Colonic flora are known to catalyze the breakdown of flavonoids. It was also found that suppressing the breakdown of quercetin by intestinal flora is important for achieving higher concentrations of quercetin in the plasma. Soy isoflavone aglycone is absorbed faster and in higher amounts than glucosides in humans. Some dietary components are also known to affect the absorption of isoflavones. Human metabolism and excretion of isoflavones following the consumption of soy products show considerable variation. The bioavailability of soybean isoflavones to women is dependant on gut microflora. Equol is a metabolite of daidzein produced by intestinal flora. Equol has many biological activities relates to human health, and its production might be affected by dietary composition and intestinal floral composition. To achieve higher production of equol from daidzein in the gut, control of the metabolic activity of intestinal flora might be of importance.
The effects of Escherichia coli on the transformation of bile acids were examined in aerobic and anaerobic culturing systems for 4 days. Bile acids were converted to methyl ester dimethylethylsilyl ether derivatives and determined by capillary gas liquid chromatography. E. coli oxidized cholic acid (CA) and chenodeoxycholic acid (CDCA) to 3α, 12α-dihydroxy- 7-oxo-5β-cholanoic acid (3α12α 7=O) and 3a-hydroxy-7-oxo-5β-cholanoic acid (3α7=O), and reduced these oxo-bile acids to CA and CDCA, respectively. These oxidation and reduction reactions occurred in both aerobic and anaerobic cultures, finally attaining certain equilibrium values. The values, or oxidation/reduction ratios, were 9 or more in the aerobic culture, and about 1 in the anaerobic culture. E. coli also oxidized taurocholic acid in the aerobic culture, but not in the anaerobic culture.
Immune Milk Product (40% WPI Plus, Whey Protein Isolate Plus) was administered tohealthy female volunteers and the effects on the intestinal environment and defecation frequency were examined. A non-Immune Milk Product was used as the control in the experiments. For the investigation of defecation frequency and fecal properties, 60 volunteers were assigned to two groups (30 volunteers each). One group consumed 20 g of Immune Milk Product daily followed by the control period. The other group consumed 20 g of Immune Milk Product daily after the control period. Both test period and control period were 3 weeks. Ten volunteers of each group were assigned for the test of intestinal environment. The fecal bacterial flora, fecal pH, water content, and fecal ammonia content were examined. Immune Milk Product did not alter the fecal ammonia content. The percentage of Bifidobacterium in the fecal flora was increased by the intake of Immune Milk Product. The number of Clostridium perfringens (lecithinase-positive) was slightly decreased by the intake of Immune Milk Product after 3 weeks. The defecation frequency was significantly increased by the intake of Immune Milk Product. These results suggest that the intake of Immune Milk Productis effective for improving the intestinal environment, fecal properties, and defecation frequency.
This intestinal flora study was a part of the Akakura Study, which was carried out to determine the cadmium (Cd) absorption rate from ordinary diets in humans by comparing Cd content in the diet with that in the feces and urine. This report describes the composition and changes of intestinal bacterial flora among young Japanese females living together in the same dormitory and eating the same Cd-controlled diets. Subjects consumed the same menus designed by a dietician for two weeks. Before and after the study, subjects completed a profile of mood states (POMS) questionnaire to ascertain stress levels. Fecal samples were collected and the flora analyzed at three points during the study. The mean wet and dry weights of feces per day were 98.6 g (74.2-136.7) and 21.0 g (16.3-25.4), respectively. The total number of bacteria did not change significantly during the study period. Bacteroidaceae, Eubacterium, Bifidobacterium, Enterobacteriaceae, Streptococcus and Lactobacillus were recovered from all subjects, while Bacillus and Peptococcaceae were obtained from about half of them. The major components were Bacteroidaceae, Eubacterium, and Bifidobacterium. The next common species were Enterobacteriaceae, Streptococcus, and Peptococcaceae, Lactobacillus, and Clostridium other than C. perfringens. C. perfringens, yeast and Megasphaera were present rarely or occasionally. As a stress level, mean POMS fatigue and depression scores were unchanged throughout the study, the vigor score increased and the tension-anxiety score decreased compared to those before starting the study. There were no significant differences in the composition of fecal flora among individual subjects. The total number of bacteria tended to decrease over time, but the change was not statistically significant. The proportions of Bifidobacterium and Bacteroidaceae tended to increase. Lactobacillus also tended to decrease in all participants, and it was not related to the removal of milk and yogurt from the diet. It is not clear what part of the diet caused these differences.
Lactulose has been shown to modify the gut microbiota in increasing bifidobacteria and reducing the numbers of clostridia. In this pilot study we investigated whether the microbiota could be modified in infants with atopic manifestations with or without gastrointestinal symptoms. We could safely promote the bifidobacterial microbiota in symptomatic infants by feeding a low dose of lactulose. The symptoms of the children were concomitantly improved.