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We investigated the effects of various dietary fibers or their likenesses on the apparent fat digestibility by rats fed on a high-fat diet. Each of 23 different fibers was added at 5% (w/w) to a purified diet containing 20% (w/w) corn oil. The rats were fed these diets for 2 weeks, and the feces were collected from each animal during the last 3 days. When compared with cellulose (control), 10 of the tested fibers significantly increased the fecal lipid excretion. Among these fibers, chitosan markedly increased the fecal lipid excretion and reduced the apparent fat digestibility to about a half relative to the control. The apparent protein digestibility was not greatly affected by chitosan. The fatty acid composition of the fecal lipids closely reflected that of the dietary fat. These results suggest that chitosan has potency for interfering with fat digestion and absorption in the intestinal tract, and for facilitating the excretion of dietary fat into the feces.The beneficial effects of dietary fiber have attracted strong attention. These benefits are not only recognized as being a reduction in the energy density of a diet!) and an increase in the stool weight or in the frequency of defecation,2) but also as a preventive measure against disorders prevalent in the lower intestinal tract, e.g., diverticulitis or colon cancer.3) The effects of dietary fiber on lipid metabolism have been extensively studied, and there are many reports concerned with their effects on serum and liver lipids.4 6) There is, however, little information on the total lipids excreted into the feces concomitantly with the

Several chitosan preparations, either with a comparable degree of deacetylation but differing viscosity or with comparable viscosity but a differing degree of deacetylation, were examined for their effect on the fecal fat excreted from rats fed on a high-fat diet. As the viscosity or deacetylation degree of a chitosan preparation increased, the more its effect on the apparent fat digestibility by rats became conspicuous. A supplement of ascorbic acid to each chitosan diets resulted in a significant depression of fat digestion and absorption in the lumen. The chitosan intake caused a higher level of fat to be excreted in the feces of the corn oil-receiving rats than the lard-receiving ones, although the effect was strong with both diet groups.

Rats were fed for 2 weeks on five different high-fat diets containing cellulose (control) or chitosan with and without organic acids (i.e., ascorbic, lactic and citric acids) as the dietary fiber. The apparent fat digestibility in the chitosan-receiving groups was significantly lower than in the control group. The addition of ascorbic acid to chitosan caused a larger increase in the fecal fat excretion than otherwise, without considerably affecting the apparent protein digestibility.The effect is thought to have occurred because chitosan was so well dissolved and mixed with fat by the action of ascorbic acid that it encapsulated fine fat droplets on its gel after contacting the pancreatic juice in the samll intestine. The intake of a mixture of chitosan and ascorbic acid is suitable for reducing excess fat.Chitosan is an N-deacetylated product of chitin, and its basic structure is (1-4 )-linked 2-amino-2-deoxy-f3-D-glucan. Chitosan has been shown to have potent hypocholesterolemic effects 1,2.3) and physiological functions. .5 ) In particular, the hypocholesterolemic effect of chitosan has been extensively studied. 1 -3.6 -8) The most acceptable explanation for the effect of chitosan is that chitosan interacts with acidic and neutral steroids in the intestinal lumen and increases their fecal excretion. )We have previously reported that chitosan caused a marked increase in the fecal excretion of dietary fat given to rats, although chitin, which in a sense is "acetylated chitosan", did not have such an effect. * 1