Fermentation of Vegetable Fiber in the Intestinal Tract of Rats and Effects on Fecal Bulking and Bile Acid Excretion

Abstract

The fermentative breakdown and fecal bulking capacity of dietary fiber from various vegetables (carrots, rutabagas, peas, green beans and Brussels sprouts) were evaluated in balance experiments in rats. The excretion of bile acids, protein and fat was also studied. The addition of blanched vegetables providing 10 g of fiber/100 g of diet caused a two-(rutabagas) to threefold (carrots) increase in fecal dry weight compared to that with a basal fiber-free diet. With green beans and Brussels sprouts, only about 25% of the fecal dry weight could be accounted for as fiber, whereas with the other investigated vegetables, 40-47% was fiber. Of the remaining part, 11% on average was fat, and 18% was crude protein. Fiber in carrots and peas was the least degraded, with approximately 47% of the polysaccharide intake being excreted in feces. By contrast, the breakdown of the fiber in green beans and Brussels sprouts was more extensive, with a mean of 23% of the polysaccharides being recovered. Among individual fiber constituents, glucose, mannose and uronic acids were least fermented, with considerable differences between vegetables. Total excretion of bile acids was reduced only when Brussels sprouts were added, whereas the concentration of fecal bile acids was lowered with all vegetables except rutabagas. However, no uniform change in fecal bile acid pattern could be detected.

Crude Fibre Determination of Malva sylvestris L. and Evaluation of its Faecal Bulking and Laxative Properties in Rats

“…An increase of 105% and 86% in fresh and dry faecal weights respectively was noted for fibre-fed rats when compared to the control group. These results are comparable to those obtained in similar studies carried out utilizing high-fibre containing diets (Nyman & Asp, 1982;Nyman et al, 1990;Bravo et al, 1992).…”

“…Results attained in the pharmacological investigation are expected to be reconfirmed if tested in human subjects since a correlation has been established between this rat model and humans (Nyman et al, 1990). …”

“…Even though heavily documented that M. sylvestris is laxative, supporting clinical evidence is scarce. To classify as a faecal bulking agent M. sylvestris should produce the desired effect of increasing faecal weight and faecal water content (Hamilton, Wagner, Burdick, & Bass, 1988;Nyman & Asp, 1982;Nyman, Schweizer, Tyren, Reimann, & Asp, 1990;Bravo et al, 1992).…”

Effects of Boiling and Storage on Dietary Fibre and Digestible Carbohydrates in Various Cultivars of Carrots

“…Thus, earlier studies in man showed an increased faecal bulk when carrots (200È688 g) (Robertson et al 1979a ;Wisker et al 1994) or carrot Ðbre (20 g) (Cummings et al 1978) were added to the diet for 3 weeks. Similar e †ects have been demonstrated in rats (Nyman et al 1990(Nyman et al , 1991. However, the e †ect of processing is less clear.…”

Digestion-Resistant Remnants of Vegetable Vascular and Parenchyma Tissues Differ in Their Effects in the Large Bowel of Rats

“…Structural tissues located in the rind are characterized by fibres and xylem vessels with secondarily thickened cell walls embedded in parenchymatous ground tissue. As they contain a higher proportion of cellulose and lignin than thin-walled parenchyma, they may be more resistant to hind gut fermentation, so they may have a valuable role in conferring the wide range of benefits to large bowel health that are thought be derived from bulk in the distal colon [11,25].…”