Colonic bacteria ferment nutrients escaped digestion and absorption in the small intestine to get energy for their proliferation, and result in luminal accumulation of their fermentation products. Colonic fermentation and their products are influenced by available substrates which vary chemical compositions and physical states. Plant fibers, resistant starch, nondigestible oligosaccharides and resistant proteins are principal substrates for colonic bacteria, and are anaerobically metabolized to various organic acids, mainly short—chain fatty acids (acetate, propionate and butyrate), ammonia and amines. Short—chain fatty acids are rapidly absorbed across Colonic mucosa and used as an energy nutrient. Short—chain fatty acids, besides their energy supplier, play a role as luminal chemical stimuli that can modify epithelial proliferation, intestinal blood flow, motility and secretion. The effects vary among short—chain fatty acids, and are dose—dependent. The sensory mechanism, therefore, of the gastrointestinal tracts must be able to detect not only the presence of individual short—chain fatty acids, but also their concentration.

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The effect of partially hydrolyzed guar gum on elevation of blood glucose and insulin secretion after sucrose intake was investigated in six healthy human volunteers. When sucrose 30g was taken by subjects, the peak of blood glucose and insulin levels was recognized at 30 min. after ingestion. When 5g of partially hydrolyzed guar gum was taken simultaneously with sucrose 30g, blood glucose level at 60 min. after ingestion was significantly (p<0.05) lower than that of sucrose alone. Serum insulin level was also lower than that of the control, but there was no significant difference between two groups. Although viscosity of partially hydrolyzed guar gum is greatly lower than that of intact guar gum, the reduction effect of blood glucose level after sucrose intake was remained.

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Effects of partially hydrolyzed guar gum on the gastrointestinal function were studied. The fine structure of the intestinal mucosal surface was observed by scanning electron microscopy in rats fed a partially hydrolyzed guar gum diet for four weeks. The surface structures of ileal and cecal mucosa changed markedly abnormal in the rats fed the partially hydrolyzed guar gum diet; their microvilli of partially hydrolyzed guar gum diet group were more tightly packed than those of the cellulose diet group, and some intestinal contents adhered much more to the tops of the microvilli in the partially hydrolyzed guar gum diet group. The rats fed the partially hydrolyzed guar gum diet showed a significant increment in the weight of the cecum and in its contents, and decrement in the fecal weight, in comparing with those fed the cellulose diet. The transit time of gastrointestinal tract was extended by the partially hydrolyzed guar gum supplementation. In conclusion, the partially hydrolyzed guar gum feeding exerted effects on the ileal and cecal mucosal surface structure, and it is suggested that these effects are related to the viscosity of the intestinal contents.

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The effects of cooking on the contents of dietary fiber in 11 kinds of vegetables were studied using Prosky method and modified Prosky method, and the contents of dietary fiber measured by both methods were compared in each other. In the modified Prosky method, dietary fiber values were determined without subtraction of crude protein (nitrogen×6.25) in enzyme digested residue. Boiling or simmering increased the amounts of dietary fiber in carrot, edible burdock, onion and cabbage, but noticeably decreased those in santohsai, Chinese chive and Chinese cabbage. Frying and deep-frying increased the amounts of dietary fiber in carrot, edible burdock, Japanese radish, cabbage, spinach, santohsai, Chinese cabbage and sweet pepper, but decreased those in onion, Chinese chive and komatuna. The content of crude protein in enzyme digested residue was greater in leafy vegetables except cabbage(44-126mg/g) than in root vegetables(24-37mg/g), and was further increased by cooking in most kinds of vegetables. The contents of dietary fiber determined by the modified Prosky method were 10 to 50% larger than those determined by Prosky method in raw leafy vegetables, but in root vegetables the contents of dietary fiber determined by both methods were not so different each other. From above results it was supposed that the composition of nitrogen containing compounds in enzyme digested residue was needed for the accurate determination of the content of dietary fiber especially in leafy and cooked vegetables.

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Effects of ingestion of LS-cookies containing galactosylsucrose (LS) were investigated on defecation, fecal condition and microflora in 19 healthy female students, and compared with those of placebo cookies or non-ingestion of any cookies. The subjects were given four pieces of placebo cookies (total 48g, without LS) daily for one week (control phase), and not fed any cookies for next one week (blank phase). Then they were given four pieces of LS-cookies (total 48g, LS 4g) daily for two weeks. The fecal microflora were analyzed on the samples of 10 subjects who were randomly selected from 19 subjects. The number of days with defecation per week was significantly increased by the ingestion of LS-cookies as compared with the ingestion of placebo cookies in the group (n=9) with the slight constipation (p<0.05). The effect of LS-cookies ingestion on defecation became remarkable in comparison with that of blank phase (p<0.05). Furthermore, the number of days with defecation per week in all subjects was significantly increased by the ingestion of LS-cookies as compared with the blank phase (p<0.05), although the significant effect was not expressed in comparison with the control phase. Fecal conditions such as volume, color, shape and hardness feeling were significantly improved by the ingestion of LS-cookies as compared with those of placebo cookies (p<0.05) and the non-ingestion (p<0.05). The ratio of beneficial microbes, Bifidobacteria, to anaerobes was increased from 22.3% to 31% and the ratio of harmful microbes, Bacteroidaceae, was decreased from 42.6% to 32.2% by LS-cookies ingestion, respectively. These results demonstrate that the ingestion of cookies (48g) containing galactosylsucrose (4g) increases the day with defecation per week, improves fecal condition such as volume, color, shape and hardness feeling and promotes the proliferation of beneficial intestinal microbes in adolescent females, in particular with slight constipation.

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