Digestion-Resistant Dextrin Derivatives Are Moderately Digested in the Small Intestine and Contribute More to Energy Production Than Predicted from Large-Bowel Fermentation in Rats

Background: Digestion-resistant dextrin derivatives (DRDDs), including resistant maltodextrin (RM), polydextrose, and resistant glucan (RG), have been developed as low-energy foods. However, data on the resistance of DRDDs to small-intestinal digestion are scarce.Objective: We sought to determine the site and extent of DRDD breakdown in the rat intestine and to predict its energy contributions.Methods: In vitro small-intestinal resistance of DRDDs was evaluated by the AOAC method for dietary fiber measurement and by artificial digestion with the use of pancreatic α-amylase and brush-boarder membrane vesicles. In vivo small-intestinal resistance of DRDDs was determined from the feces of male ileorectostomized Sprague-Dawley rats fed a control diet or a diet containing one of the DRDDs at 50 g/kg for 9 d (period 1) and then for 10 d (period 2), during which they received 1 g neomycin/L in their drinking water. Separately, male Sprague-Dawley rats were fed the same diets for 4 wk, and the whole-gut recoveries of DRDDs were determined from feces at days 8-10.Results: Small-intestinal resistances determined in vitro by artificial digestion (RM: 70%; polydextrose: 67%; RG: 69%) were lower than those measured by the AOAC method (RM: 92%; polydextrose: 80%; RG: 82%). In the ileorectostomized rats, fecal dry-matter excretions were consistently greater in the DRDDs than in the control. The small-intestinal resistances of the DRDDs were 68%, 58%, and 62% in period 1 and 66%, 61%, and 67% during period 2 for RM, polydextrose, and RG, respectively. The resistances did not differ among the DRDDs at either time. In the normal rats, food intakes and body weight gains did not differ among the groups. The whole-gut recovery of RM (13%) was lower than that of polydextrose (33%) and RG (29%), which did not differ.Conclusions: DRDDs were more digestible in the rat small intestine than the AOAC method. The energy contribution from small-intestine digestibility, not just large-bowel fermentability, must be considered in determining the energy contribution of DRDDs. Whether humans respond similarly needs to be tested.