In the present paper, I summarize the data suggesting the effects of dietary fiber on the function of the upper gastrointestinal tract. The chemical and physical properties of dietary fibers are associated with gastrointestinal functions that have important metabolic implications for health. Both properties of dietary fiber include viscosity, bulking capacity and fermentability. These properties are associated with morphological changes, crypt cell production, intestinal mucin secretion, the activity of small intestinal brush border enzymes and gastrointestinal peptides (gut hormones). A variety of experimental method will lead to different observations. This discrepancy may be due to the level and type of fiber added. Further studies are needed to establish the effect of human gastrointestinal tract by the adequate experimental conditions. It is also expected that these observation are adopted to the clinical nutrition such as prevention of metabolic syndrome, parenteral nutrition, and gut disease.

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Non-treated high-amylose corn starch (HAS) and heat-moisture-treated HAS (HMT) are resistant starch enriched foodstuff. In this study, we examined the influence of resistant starches of HAS and HMT on cholesterol metabolism of Wistar rats fed a high-fat and high-cholesterol (0.25%) diet either containing 20% of untreated corn starch (control group), HAS (HAS group) or HMT (HMT group) for 18 days. Fecal weights of the HAS or HMT were significantly higher than that of control group, and that of HMT was significantly higher than that of HAS group. Fecal cholesterol excretions of the HAS or HMT groups were higher than that of the control group. Fecal bile acid excretion of the HAS or HMT groups were significantly higher than that of the control group. Liver cholesterol 7α-hydroxylase activity increased significantly in the HMT group. Serum and liver cholesterol levels remained unchanged in the HAS and HMT groups. These results showed that the ingestion of HAS and HMT effectively functioned as dietary fiber supplement and accerarated fecal bile acid excretion.

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We examined the effect of fat and oil intake during growth period on preferential fat intake in adult rats using high-fat diet (HFD) with cellulose added to maintain the same metabolizable energy concentration as low-fat diet (LFD). Four groups of 4 week-old male Fischer 344 rats were fed either LFD (LFD group) or one of three kinds of HFD with cellulose added (lard HFD, soybean oil HFD and fish oil HFD group). After 8 weeks, three HFD groups were placed on a self-selection regimen of LFD and each HFD for 3 weeks to examine the ratio of HFD and LFD intake. No significant difference in calorie intake and body weight was observed among all groups through the experimental period. However, during self-selection period, ratio of HFD intake [HFD intake (g)/total intake (g)] for fish oil HFD group was lower than that of lard and soybean oil HFD group. Within first week after self-selection regimen, the ratio for lard HFD, soybean oil HFD and fish oil HFD group was 50%, 30% and 17%, respectively. However, the ratio for lard and soybean oil HFD group decreased and reached about 20% within third week after self-selection regimen. The amount of fat intake was calculated 6g/100g diet. These findings indicated that (1) lard HFD has food properties preferable to soybean oil HFD and fish oil HFD, (2) HFD with cellulose added to maintain the same metabolizable energy concentration as LFD guards against overfeeding of fats.

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