Dairy Product Intake Alters the Correlations between Circulating Bile Acids and Short-Chain Fatty Acids with the Bacterial Taxa Roseburia, Faecalibacterium, Flavonifractor, and Verrucomicrobia

INTRODUCTION: Type 2 diabetes (T2D) risk factors are associated with gut microbiota dysregulation that can alter circulating metabolite levels such as bile acids (BAs) and short-chain fatty acids (SCFAs). The objective was to investigate how the high dairy (HD) (≥4 servings/day) product intake compared to adequate dairy (AD) (≤2 servings/day) intake influences the correlations between Roseburia, Faecalibacterium, Flavonifractor, as well as Verrucomicrobia and circulating BAs and SCFAs in subjects at risk of T2D. METHODS: In a randomized crossover trial, 10 hyperinsulinemic adults were randomized to HD or AD for 6 weeks separated by a 6-week washout period. Gut microbiota were measured with 16S rRNA-based high-throughput sequencing. BA profiling in plasma was performed by high-performance liquid chromatography-tandem mass spectrometry. Serum SCFAs were determined using headspace gas chromatography. RESULTS: No significant differences were observed in mean circulating BA or SCFA levels between AD and HD consumption. Verrucomicrobia and Flavonifractor showed positive correlations with secondary BAs following HD and AD intake, respectively. Additionally, Flavonifractor correlated positively with acetic and propionic acids after HD intake. Roseburia correlated positively with primary BAs, propionate, and butyrate after HD intake. Faecalibacterium was positively correlated with cholic acid after AD intake and with hexanoic acid after HD intake. CONCLUSION: These findings suggest that HD intake may modulate microbiota-metabolite interactions without altering circulating metabolite concentrations, highlighting a potential role for dietary patterns in shaping gut-derived metabolic signals in individuals at risk of T2D.