Decreasing Effect of Chitosan on the Apparent Fat Digestibility by Rats Fed on a High-fat Diet

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. 66) There is, however, little information on the total lipids excreted into the feces concomitantly with the ingestion of dietary fiber. Slavin and Marie@ have reported that ingesting cellulose did not a&t the fecal lipid excretion. De Scrijver et al,*) suggested that the apparent protein digestibility was reduced to some extent by the intake of oat bran, but the apparent fat digestibility not as much. Pectin stimulated the discharge of fecal steroids?) but affected the total lipid excretion to a lesser extent. lo) It is generally accepted that apparent fat digestibility is not as much affected by dietary fiber as that of protein."~ 12) If certain dietary fibers can reduce only the fat digestibility, a reduced caloric intake will be achieved by their ingesting without a%zcting protein nutrition. In this study, we investigated the effect of various fibers on the apparent digestibility of both fat and protein in rats fed with high-fat diets.