Many studies have been reported that dietary wheat bran, cellulose, resistant starch and inulin suppressed experimental colon tumors or cancer in rats. Dietary fiber reduces contact between the intestinal contents and mucosa, and leads to production of short-chain fatty acids, acetate, propionate, and butyrate, which reduce pH and the conversion of primary to secondary bile acids. Butyrate is the major source of energy for the distal colon and it reduces cell proliferation and induces apoptosis, factors that are associated with inhibition of the transformation of the colonic epithelium to carcinoma. On the other hand, dietary fiber is thought to protect against colorectal cancer in human but this view has been challenged by recent cohort studies that showed no protective effect.

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The effects of young barley leaf powder(YBLP) on defecation frequency and fecal characteristics were studied in 61 healthy volunteers(34.1 ± 10.2 years old). The subjects were divided at random into 4 groups;non-dose control group(CG), low-dose group(LG), middle-dose group(MG), and high-dose group(HG). Total examination period was 4 weeks. After one week as the pre-test period, all groups were given a placebo diet for one week(placebo period). For the following 2 weeks(test period), CG, LG, MG and HG was given a placebo diet(not contained YBLP), a low-dose diet(1.5 g), a middledose diet(4.5 g) and a high-dose diet(6.0 g), respectively. In analysis, the subjects were screened under the condition that defecation frequency was below 7 times for one week of the pre-test period. This result showed that MG increased the defecation frequency and estimated fecal quantity significantly for the test period compared with those for the pre-test period, and HG increased them significantly for the test period compared with those for the pre-test period and placebo period. No clinical signs of toxicity recognized in the test period. These results suggest that YBLP has a fecal bulking effect and is useful for safety food material.

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Effects of a daily intake of soft drink containing 4g of galacto-oligosaccharides(GOS) on defecation frequency, fecal properties and fecal microflora were evaluated by a double-blind crossover study in 51 healthy female students (average age 19.7±1.2 y). The subjects were divided into two groups and given a 60 mL/day (containing 4 g GOS) of soft drink or a placebo drink for three weeks each with two weeks interval. Seventeen subjects of them, whose viable Bifidobacterium counts in feces were less than 30% of the total fecal bacterial counts, were analyzed for their fecal microflora before and after the both drinks intake period. As a result, after the GOS drink intake, in 28 subjects whose defecation was less than five days per week, significant increases in defecation frequency and fecal volume were observed compared to the placebo drink intake (p<0.05) or the non-intake period (p<0.01). Fecal microfloral analysis revealed the number of total anaerobic bacteria and Bifidobacteria to have increased significantly compared to the placebo drink intake (p<0.05) or the non-intake period (p<0.05, p<0.01, respectively), and the occupation percentage of Bifidobacteria in the total count of fecal microflora was tended to increase compared to the placebo drink intake or significantly increased compared to the non-intake period (p<0.05). On the other hand, the number of Clostridium lecithinase (+) significantly decreased compared to the non-intake period (p<0.05). Furthermore, in 6 subjects, whose viable Bifidobacterium counts in feces were less than 10% of the total fecal bacterial counts before the GOS drink intake period, the number of Bifidobacteria and Lactobacilli increased significantly, and the occupation percentage of Bifidobacteria in the total count of fecal microflora was significantly increased compared to the non-intake period (p<0.05, respectively). These results clearly show that the daily intake of the soft drink containing 4g GOS per 60m1 contributes to improve defecation and fecal properties through its prebiotic effects on increasing useful intestinal bacteria and simultaneous decreasing harmful intestinal bacteria to keep a good intestinal environment.

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In order to evaluate the available energy of dietary fiber materials, the fermentability was estimated from breath hydrogen excretion for 8 h after ingestion of 5g of dietary fiber materials in healthy human subjects. Fructo-oligosaccharide, of which available energy has been 2kcal/g, was used as a positive control, because it is not digested and is completely fermented by intestinal microbes. The following results were obtained based on the variable fermentability of each dietary fiber material. 1) Polydextrose, indigestible dextrin, partially hydrolyzed guar gum, lowered molecular alginate-Na and glucomannanwere estimated as 1 kcal/g. 2) Nondigestible starch, which was resistant for the fermentation by intestinal microbes, was estimated as Okcal/g. 3) Cellulose, which is a water-insoluble dietary fiber, was slowly fermented and was estimated as l kcal/g.These results demonstrate that the method using breath hydrogen analysis is available to estimate the fermentability of dietary fiber in human gastrointestinal tract. However, it was not enough to collect expiratory gas of every 30 min period for 8 h after ingestion of dietary fiber materials. The fermentation of each dietary fiber material did not have been finished yet till 8 h after ingestion. Therefore, if the breath is collected for longer periods, the fermentability might increase and the available energy would be changed from the values as mention above. Another study with longer periods of breath collection will be needed.

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In the present study, the effect of oligosaccharide fragments (MW 286-930) obtained enzymatically from corn branhemicellulose (CBH), a soluble dietary fiber, on the development of hepatitis induced by D-galactosamine was investigated. Seventy-two male Wistar rats that were fed a diet supplemented with the oligosaccharide fragments were administered D - galactosamine intraperitoneally at a dose of 500 mg/kg and euthanized just before injection (0 h) and 1, 3, 9, 16 and 22 h after injection. Plasma endotoxin concentrations, serum cytokine levels, and serum transaminase activities were analyzed in addition to liver DNA fragmentation. The results showed that the oligosaccharide fragments significantly suppressed the increase in plasma endotoxin concentrations and significantly depressed the enhancement of serum transaminase activities and tumor necrosis factor-α (TNF-α) but showed no effect on serum interferon-γ and liver DNA fragmentation .These results suggested that the oligosaccharide fragments obtained enzymatically from CBH might protect the liver against D - galactosamine hepatitis through the suppression of both plasma endotoxin increment and serum TNF-α production.

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To elucidate the effect of Curdlan, a kind of microbial producing indigestible polysaccharides, on the health benefit in human, one pack of Tofu noodles containing 7.5g of curdlan was given to 28 healthy young female students daily for two weeks. The each subject was obliged to note 6 items to estimate daily defecation habits on the health condition recording paper for two weeks of ordinary meal (control period) and of the test food period. The present study seemed to revealed that the ingestion of curdlan containing Tofu noodles might be effective forsignificantly increasing the scores of 5 parameters compared to those of the control period ; defecation frequency (p<0.009), fecal quantity (number of model tube, p<0.002), fecal volume (consciousness, p<0.008), physical sensation after defecation (p<0.001) and stool type (p<0.003). These results suggest that curdlan may act to improve the defecation frequency and the other fecal characteristics in human.

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