(P19-003-25) Impact of Almond Consumption on the Gastrointestinal Microbiome and Metabolome in Healthy Adults

Objectives: We aimed to determine the impact of habitual almond consumption on gut microbiome composition and function, serum and fecal bile acid profiles, systemic inflammation, and oral glucose tolerance to a mixed-meal challenge.

Methods: Healthy adults (n=28; 39 ± 7 y, BMI 28.7 ± 2.4 kg/m²) were enrolled in a 12wk randomized, parallel-arm trial with two conditions: roasted almond (56g) or isocaloric control (pretzels) daily. Fecal samples were collected at baseline and week 12. At baseline and 12 wk, participants underwent 6h mixed-meal tolerance tests (75g glucose + almonds or pretzels) with repeated blood sampling every 30 min. Fecal microbiome and microbiota were assessed using amplicon (16S) and metagenomic (gDNA) sequencing, respectively. Fecal microbial metabolites were quantified using GC/MS. Blood glucose, insulin concentrations, and inflammatory biomarkers (IL-6, TNFα, CRP, and LBP) were determined. Fecal and circulating bile acids were measured via LC-MS/MS.

Results: The log-fold change (logFC) of 16S Roseburia was marginally greater in the almond group compared to the control (p = 0.14). gDNA species data revealed a positive mean logFC of R. hominis (+0.17) and R. intestinalis (+0.22) in the almond group compared to control. There was no difference in absolute butyrate concentrations nor the abundance of Butyryl-CoA:acetate CoA-transferase between groups. However, relative to the other SCFAs, butyrate abundance increased in the almond group (logFC = +0.3; p = 0.03) at the expense of propionate (logFC = -0.1; p = 0.04). Plasma glucose was negatively correlated to glycoursodeoxycholic acid (iAUC; ρ = -0.66, p < 0.01) and glycohyocholic acid (GHCA) (iAUC; ρ = -0.61, p = 0.02) in the almond challenge (pooled periods), but not with the control challenge. Fasting GHCA increased in the almond group at 12wk (logFC = +1.50 ± 4.10), which differed from the control (logFC = -2.92 ± 3.14), p < 0.05.

Conclusions: Habitual almond consumption induced purportedly beneficial changes in the intestinal microbiome and metabolome in healthy adults. Fasting and postprandial bile acid concentrations were related to glycemic responses during mixed-meal tolerance challenges.

Funding Sources: Almond Board of California and USDA NIFA AFRI (1030851)