Fermentable dietary fibers reduce voluntary alcohol intake and modulate gut microbiota composition in rats

Fermentable dietary fibers can reshape the gut microbiota and boost short-chain fatty acid (SCFA) production, processes impaired by chronic alcohol use. We compared five fibers—cellulose, pectin, resistant starch, guar gum, and inulin—in male Wistar rats. After 10 days on the test diets, voluntary alcohol intake was measured with a multiple-scheduled-access paradigm, followed by a 10-day alcohol-intoxication phase. 16S rRNA profiling showed that fermentable fibers (inulin, pectin, guar gum) lowered ethanol consumption by 40–60 % and enriched SCFA-producing Bacteroidia and Muribaculaceae while reducing Proteobacteria. These microbiota shifts persisted after repeated intoxication, indicating ecological resilience. Locomotor testing confirmed that decreased drinking was not attributable to altered activity. Low-/non-fermentable fibers (cellulose, resistant starch) had no effect on intake or community structure. Our results identify fiber fermentability as a critical functional trait and support the incorporation of fermentable fibers into functional foods aimed at microbiota-based modulation of alcohol-related behaviors. • Fermentable fibers reduce voluntary alcohol intake in a rat model. • Inulin, pectin, and guar gum modulate gut microbiota composition. • SCFA-producing bacteria increase with fermentable fiber supplementation. • Fiber-induced microbiota shifts persist after alcohol exposure.