BackgroundDigestion‐resistant dextrin derivatives (DRDDs) including resistant maltodextrin (RM), polydextrose (PD) and resistant glucan (RG) have been developed as low energy foods. However, attempts to quantify the in vivo small intestinal resistance of DRDDs are scarce.ObjectiveThe aim of this study was to determine the site and the extent of DRDD breakdown in the rat intestine and to predict their contribution to energy production.MethodsIn vitro small intestinal resistance of DRDDs was evaluated by the two methods, i.e., AOAC method for dietary fiber measurement, and artificial digestion method using a pancreatic a‐amylase and brush boarder membrane vesicles. In vivo small intestinal resistance of DRDDs was determined from feces in Sprague‐Dawley ileorectostomized rats (males aged 7 wk) fed a diet including RM, PD or RG at 50 g/ kg for 9 d (period 1) and then for 10 d (period 2), during which time they received neomycin (1 g/L) in their drinking water. Separately, Sprague‐Dawley normal rats (males aged 9 wk) were fed the same diets for 4 wk, and the whole‐gut recoveries of DRDDs were determined from feces at d8–10.ResultsThe in vitro small intestinal resistance with the artificial digestion (RM, 70%; PD, 67%; RG, 69%) was lower than those with AOAC method (RM, 92%; PD, 80%; RG, 82%). In vivo small intestinal resistance of DRDDs was RM (68%), PD (58%) and RG (62%) in the period 1, and RM (66%), PD (61%) and RG (67%) in the period 2. Digestion resistance among DRDDs was comparable in either period. The whole‐gut recovery of RM (13%) was lower than that of PD (33%) or RG (29%).ConclusionsDRDDs were more digestible in the rat small intestine than in vitro prediction by AOAC method. The energy contribution from small intestine digestibility, not just large bowel fermentability, must be considered in determining the energy contribution of DRDDs. However, the findings need to be replicated in humans.