(P22-007-24) Changes in Gut Microbiota and Plasma, Fecal, and Urinary Metabolites Following Mediterranean Diets With Varying Quantities of Lean Beef Compared to an Average American Diet

Objectives: This study evaluated gut microbiota composition and plasma, fecal, and urinary metabolomes in response to Mediterranean diets with 0.5 (MED0.5), 2.5 (MED2.5), and 5.5 (MED5.5) oz/d/2000 kcal of lean beef compared to an average American diet (AAD). The primary objective was to explore differences in metabolites, primarily trimethylamine N-oxide (TMAO) and its precursors, and gut microbiota composition by diet.

Methods: In this 4-period crossover study, 36 healthy adults consumed each diet for four weeks. Samples were collected at baseline and the end of each diet period. All metabolomics samples were prepped and analyzed using untargeted metabolomics methods through H-NMR. Statistical analyses were performed in R (version 4.3.1). Differences in individual compounds were analyzed via mixed models, adjusting for multiple comparisons with Tukey’s test. DNA from homogenized fecal samples was extracted and analyzed by sequencing the V4 region of the 16S rRNA gene on an Illumina MiSeq. Sequences were analyzed using QIIME2 (version qiime2-2023.5). Between-diet differences in alpha and beta diversity were assessed using a linear mixed effects model and the Adonis (PERMANOVA) test, respectively. Differential abundance was analyzed by ALDEx2 (version 1.32.0).

Results: TMAO was the only differential metabolite in the urine, which was higher following the AAD vs. the MED0.5 [0.59 mM (95% CI: 0.15, 1.03)], MED2.5 [0.61 mM (95% CI: 0.17, 1.053)], and MED5.5 [0.59 mM (95% CI: 0.14, 1.03)]. Choline was the only differential metabolite in the feces, which was higher following the AAD vs. MED0.5 [0.09 mM (95% CI: 0.01, 0.16)], MED2.5 [0.10 mM (95% CI: 0.03, 0.18)], and MED5.5 [0.09 mM (95% CI: 0.02, 0.17)]. No metabolites of interest were detected in the plasma. Microbiota alpha diversity (Shannon index) was lower with the AAD compared to the MED0.5, MED2.5, and MED5.5. Beta diversity (CLR euclidean) differed between AAD and MED0.5, MED2.5, and MED5.5. All three MED diets increased Lacticaseibacillus abundance compared with AAD.

Conclusions: Mediterranean diets with varying levels of lean beef resulted in lower urinary TMAO and fecal choline than an AAD. The MED diets increased alpha diversity and altered beta diversity, possibly driving the effect of lower TMAO production seen in these diets.

Funding Sources: Department of Nutritional Sciences, Penn State & Beef Checkoff