Dietary fibers exert various biological effects such as anti-cancer effect, improvement of serum lipid levels and intestinal flora, prevention of constipation, immunoregulatory activity etc. It has also been reported that water-soluble dietary fibers exert stronger immunoglobulin (Ig) production regulating activity than water-insoluble cellulose. Among them, oral administration of pectin, glucomannan, galactomannan or chitosan markedly enhanced serum IgA and IgG levels and decreased serum IgE level in Sprague-Dawley rats. They also enhanced IgA and IgG productivities of spleen and mesenteric lymph node (MLN) lymphocytes, as well as productivity of cytokines such as interferon-y and tumor necrosis factor-a of MLN lymphocytes. These results suggest that water-soluble dietary fibers regulate Ig production through the regulation of cytokine production. It has been shown that these dietary fibers and their sugar components could not stimulate Ig production of isolated lymphocytes directly . In addition, partially digested guar gum exerted weaker dietary effect on Ig production and lipid metabolism than intact guar gum. These results suggest that watersoluble dietary fibers exert their biological effects through the interaction with intestinal flora.

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The effects of dietary fiber rich cereal-based breakfast on the increment of fecal wet weight, defecation rate and condition of evacuation were investigated in normal subjects (n=36) and the data of 29 subjects selected from 36 subjects were used for the evaluation. The study design was crossover experiment for continuous 1 weeks, and the subjects consumed 2 different test cereal flakes (cereal A, B) in random order in their breakfast. Total dietary fiber contents of the test cereals for three trials were 6.4g for cereal A 40g, 9.6g for cereal A 60g and 5.Og for cereal B 60g, respectively. The cookie as the control does not contain dietary fiber. The results obtained were as follows ;1) The fecal wet weight significantly increased with cereal A 40g, A60g and also cereal B60g and the increment was dependent on the total dietary fiber contents of the test cereals, comparing to the control . 2) The defecation rate of days and times per week were significantly increased with cereal A40g, A60g and cereal B60g, comparing of the control, respectively. 3) The condition of evacuation such as fecal form, color and smell were significantly improved in cereal A 40g and cereal A60g ingestions. 4) The wet weight of feces which makes feel defecation every day was approximately 150g. We concluded that dietary fiber rich cereal-based breakfast has a fecal bulking effect and the improvement of condition of the evacuation in the additional ingestion of 5.0-6.4g of dietary fiber in a day.

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To evaluate the effects of two different fractions of barley bran on gastrointestinal function and lipid metabolism, five weeks old male Sprague-Dawley rats were fed diets containing cellulose powder (control), wheat bran (WB), outer layer of barley bran (BB-30) and inner layer of barley bran (BB-60) at 5% dietary fiber level for 4 wks. An increase of cecal weight, a lowered pH of cecal contents and a shortening of gastrointestinal transit time in the BB-60 group were significant in comparison with those in the other three groups, respectively. Fecal moisture and butyric acid production in cecal contents of the BB-60 group were significantly higher than those of the BB-30 group. The hepatic cholesterol and triacylglycerol concentrations in the bran-fed groups were significantly higher or higher tendency than those in the control group. These results suggest that BB-60 is different from BB-30 and rather similar to WB on some aspects of gastrointestinal functions, and this phenomenon may be attributed to the difference of dietary fiber composition.

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The moderating effect of indigestible dextrin on postprandial rise in blood glucose level after sucrose loading has been well demonstrated. In this study we conducted a continuous ingestion study in WBN/Kob rats, which is known a spontaneous type-2 diabetes model, in order to evaluate the preventive effects of indigestible dextrin on aggravation of both glucose and lipid metabolism caused by the high-sucrose diet. By ingesting the high-sucrose diet, glucose tolerance after sucrose loading was impaired, both fasting blood glucose and plasma total-cholesterol levels were increased, and fat accumulation was increased after four weeks in WBN/Kob rats and after eight weeks in Wistar rats, respectively. Despite the WBN/Kob rats kept on the high-sucrose diet, both the impairment of glucose tolerance and fat accumulation were prominently alleviated by continuous ingestion of indigestible dextrin. Contrary, no preventing effect of pectin and corn-fiber on deterioration of glucose metabolism was observed in the high-sucrose fed WBN/Kob rats.

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