(P21-06-26) A Systematic Literature Review of the Influence of Different Dietary Patterns on Fecal Bile Acids

Objectives: Bile acids (BAs) are cholesterol metabolites that regulate lipid digestion and metabolic signaling and are increasingly implicated in gastrointestinal cancers and metabolic disorders. Diet is an important driver of gut microbial bile acid (BA) metabolism. However, current review studies have focused on individual nutrients rather than overall dietary patterns. Given evidence that dietary patterns modulate the gut microbiome and BA metabolism, this systematic review assessed the influence of different dietary patterns on the fecal BA pool.

Methods: A systematic literature search was conducted following a registered protocol (PROSPERO CRD420251005380) and the PRISMA guidelines, using the electronic databases PubMed, Web of Science, and CINAHL. Observational and interventional studies involving adults (≥18 years) that evaluated dietary patterns and fecal BA outcomes were included. Two independent reviewers screened studies, extracted data on study characteristics, dietary exposures, and fecal BAs, and completed study appraisal using the NIH quality assessment tools for systematic reviews. Findings were synthesized using a thematic narrative approach.

Results: Fifty-one studies met inclusion criteria, spanning six distinct dietary patterns; high-fiber/plant-based diets (n=9), vegetarian/vegan or low-meat diets (n=11), Mediterranean dietary patterns (n=7), Western or high-fat/animal-based diets (n=12), macronutrient-modified diets (e.g., high-fat or low-carbohydrate) (n=7), and geographic-based dietary comparisons (n=5).

Plant-based dietary patterns were associated with lower fecal total and secondary BAs, deoxycholic acid (DCA), and lithocholic acid (LCA). In contrast, Westernized diets high in fat and animal products were associated with higher total, primary, and secondary BAs. Population comparisons, including African Americans versus rural Africans and Japanese American migrants versus native Japanese, similarly showed higher DCA and LCA among groups consuming Westernized diets. There was a significant variation across studies regarding BA extraction methodologies and reporting.

Conclusions: Overall, plant-dominated dietary patterns were associated with lower fecal concentrations of total BAs, primary BAs (CA and CDCA), and secondary BAs (DCA and LCA).

Funding Sources: No funding was received for this work.