(P21-002-24) Dietary Quality Impacts the Gut Microbiome and Is Associated With Neighborhood Socioenvironmental Characteristics

Objectives: African American/Blacks (AA/B) have higher rates of colorectal cancer (CRC), which is linked with modifiable risk factors like diet, the gut microbiome, and fecal microbial metabolites. Given that economic and structural inequities are barriers to dietary quality, we sought to investigate associations between dietary quality, the gut microbiome, and neighborhood socioenvironmental characteristics in human participants.

Methods: One hundred and thirty-eight participants aged 45-75 were recruited from two urban academic medical institutions in the Chicago metropolitan area. Stool and anthropometrics were collected and dietary intake data were gathered through two 24-hour dietary recalls. Diet quality was calculated using the Healthy Eating Index 2015 (HEI-2015) and participants were dichotomized using the USDA cut-point for low dietary quality ( < 51). Fecal bile acids were quantified utilizing LC/ESI-MS/MS. Stool metagenomes were analyzed for differences in diversity and taxonomic features among groups. Participant addresses were geocoded and merged with neighborhood variables to contextualize dietary quality within the broader context of the neighborhood environment.

Results: Participants were 57% female and 52% AA/B with a mean age of 59.6 (±6.2) and BMI of 31.4 (±6.9) kg/m². Participants with poor dietary quality (N=66) were more likely to self-identify as Black, report lower household incomes, and live in neighborhoods with higher poverty and food insecurity. The proinflammatory secondary bile acids lithocholic acid and deoxycholic acid were more abundant in individuals with poor dietary quality. Differential taxonomic analysis revealed 77 genera associated with poor dietary quality including Faecalitalea, Turicibacter, Fusobacterium, Parabacteroides, Desulfovibrio, and Bilophila which have been previously associated with CRC.

Conclusions: Overall, poor dietary quality was associated with deleterious secondary BA metabolites and bacterial genera that have been previously linked to CRC. Given these findings, mechanistic and interventional studies are warranted to evaluate the impact of improving food access and diet quality on microbiome composition, host microbial BA metabolism, and CRC risk among AA/Bs.

Funding Sources: LTH, PG, EM, JR, HRH: R01CA204808, U54MD012523; MLO: T32CA057699; PSB: Purdue Lynn Fellowship