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

Abstract

Many health benefits of plant-derived foods have been attributed to their dietary fibre content; however, it is the post-ingestion continuation into the gut of the properties and morphology of plant tissues based on cell walls and their survival in undigested vegetable remnants, rather than dietary fibre per se as an analyte that is of benefit in the gut. Here, we report results of experiments aimed at showing how the structure and function of different tissuesparenchymatous pith and vascular rind-within the same plant can have markedly different nutritional "functionality" in the large bowel. Eighty percent ethanol-insoluble residues from the rind and pith of broccoli stems were included at 12.5% in rat diets. Rind greatly increased faecal dry matter, hydrated faecal output, colonic water-holding capacity and theoretical water passage through the colon, whereas pith did not. Faecal bulking indices (wheat bran= 100), indicated in the following, were markedly different (p<0.001; LSD, 18.3): broccoli rind, 135; broccoli pith, 21; whole broccoli frame, 110. The apparent persistence of water-holding capacity in the feces was 2.0% for pith and 29.6% for rind, and apparent persistence of total dietary fibre was 18.2% for pith and 73.3% for rind. The results show that the effects of digestion-resistant vegetable remnants in the large bowel are strongly dependent on their tissue of origin in the plant and its function in the plant and cannot be predicted from the dietary fibre content of the plant material consumed.

Effects of Potato Fiber and Potato‐Resistant Starch on Biomarkers of Colonic Health in Rats Fed Diets Containing Red Meat

“…A reduction in fecal excretion (Table 3) and higher SCFA concentrations in the cecum and colon (Table 4) of rats fed potato fiber diet probably reflect the nature of the cell walls that constitute potato fiber. They are thin parenchymatous walls containing dispersed pectins and hemicelluloses with little cellulosic secondary thickening, and have been shown to be extensively fermented and contribute little to fecal bulk in rats (Monro and Mishra 2010). …”

Food Structure and Carbohydrate Digestibility

“…A starch fractions of different digestibility defined in caption to Figure 3. B Theoretical blood glucose response curves based on RDS and SDS release with glucose disposal allowed for using the method of Monro et al (2010). Error bars are standard deviations (Mishra and Monro, unpublished).…”

Effects of kiwifruit and mixed dietary fibre on faecal properties and microbiota in rats: a dose–response analysis

“…Mastication, digestion and gastrointestinal contractions disintegrate plant tissue structure, leaving remnants that consist largely of disperse primary cell walls containing a high proportion of pectic polysaccharides (Sims & Monro, ). Therefore, they are likely to be extensively fermented, with limited potential to contribute to faecal physical properties‐hydrated bulk and water‐holding capacity in the colon (Monro & Mishra, ).…”