Dietary Fiber Alleviates Gut Microbiota Dysbiosis Caused by High Bile Acids

Abnormal bile acid (BA) levels often accompany rising nutritional chronic metabolic diseases (hyperlipidemia, diabetes, and obesity). BAs regulate glucose, lipid, and energy metabolism, and gut microbiota mediate their metabolism, so aberrant BAs disrupt microbiota and impair health. To avoid time-consuming and complex animal/human trials, this study used the in-vitro colonic simulation system to focus on dietary fiber and gut microbiota. The research results show that high BA (4.64 g/L) reduced microbial alpha diversity, enriched opportunistic pathogens (e.g., Escherichia-Shigella, Klebsiella), inhibited Bifidobacterium, and altered BA-metabolizing enzymes (BSH, 7α-HSDH). Individual fibers (arabinose (Ara), galactooligosaccharide (GOS), mannooligosaccharide (MOS), resistant dextrin (RD), and stachyose (St)) showed type-dose-dependent regulation, while the composite dietary fiber formula (ZH, containing 10.53% Ara, 21.05% GOS, 5.26% MOS, 52.63% RD, and 10.53% St) significantly increased propionic acid, reduced pathogens, enriched Limosilactobacillus, and modulated BA metabolism. This study provides a theoretical basis for using dietary fiber to counteract BA-related microbiota dysbiosis.