Different Efficacy of Five Soluble Dietary Fibers on Alleviating Loperamide-Induced Constipation in Mice: Influences of Different Structural Features

Different dietary fibers have distinct structures, leading to significant variations in their laxative effects. To explore how these structural differences impact constipation intervention, a 14-day study was conducted on loperamide-induced constipated mice using five dietary fibers: soluble dietary fiber from steamed sweet potato (SDF-S), oat β-glucan (OB), polydextrose (PD), arabinogalactan (AG), and inulin (IN). The results showed that four fibers, excluding PD, significantly improved gastrointestinal (GI) transit rate (p< 0.05), although PD had the highest fecal moisture, it was significantly different from the lowest IN (p< 0.05). AG and IN resulted in higher 6 h fecal weights compared to other fibers. SDF-S and OB were more effective in modulating serum levels of gastrointestinal hormones. The different monosaccharide compositions and glycosidic bonds of these fibers led to distinct changes in gut microbiota composition and SCFA profiles. Galactose and arabinose in AG were linked to increased abundance ofLachnospiraceae_UCG-006,Bacteroides, andOdoribacter, promoting butyrate fermentation, which is positively correlated with GI transit rate. Glucose in SDF-S, OB, and PD favored acetate fermentation positively correlated with fecal moisture. Fructose in IN encouraged the proliferation ofMuribaculaceae_unclassifiedandRuminococcus, associated with butyrate fermentation and increased 6 h stool weight, respectively. The β-glycosidic bonds in OB may lead to high butyrate production through the selective proliferation ofLachnospiraceae_unclassified. Minor components like fucose, rhamnose, and ribose were positively correlated with the abundance ofOscillospiraceae_unclassified,Anaerotignum, andLachnospiraceae_unclassified. In conclusion, the unique monosaccharide compositions and glycosidic bond differences in dietary fibers selectively promote the proliferation of fiber-degrading and butyrate-producing bacteria, resulting in varied effects on constipation relief.