Abstract A066: Socioenvironmental contributors to dietary cysteine, the gut microbiome, and CRC disparities

Abstract Objective: Black Americans have higher colorectal cancer (CRC) incidence and mortality than other racial and ethnic groups. Our previous research revealed bacteria that produce hydrogen sulfide (H2S) are significantly associated with CRC in Black participants. Hydrogen sulfide is a genotoxin produced by the colon and the gut microbiome via cysteine metabolism. Cysteine is an amino acid abundant in animal protein and a food additive in ultra-processed foods. Given that economic and structural inequities are barriers to dietary quality, we sought to investigate associations between intake of ultra-processed foods, the gut microbiome, and presence of adenoma in participants. Methods: One hundred and thirty-eight participants aged 45-75 were recruited from two urban academic medical institutions in Chicago IL. Stool and anthropometrics were collected, and dietary intake data were gathered through two 24-hour dietary recalls. Dietary data was classified using the NOVA classification system and recategorized into 18 subcategories to determine nuances in ultra-processed food intake. 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). Stool metagenomes were analyzed for differences in diversity and taxonomic features. 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% Black 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. Grocery store access was negatively correlated with BMI and positively associated with HEI. Dietary cysteine intake was positively associated with total number of adenoma when controlling for kcal, age, gender, marital status, race, educ, site, kcal of alcohol, hhincome, BMI, and smoking. Analysis of NOVA subcategories revealed ready to eat dishes and processed food ingredients to be significant contributors of cysteine in NOVA 4 foods and participants with lower HEI consumed more ready to eat dishes. Microbiome analyses revealed significantly different features in participants consuming a high cysteine diet including genes for amino acid metabolism. Conclusions: Dietary cysteine intake is positively associated with adenoma as well as differences in the microbiome that may contribute to increased CRC risk. Processed food ingredients and ready to eat foods may be underappreciated sources of dietary cysteine abundant in a poor food environment. Citation Format: Patricia Wolf, Apekshya Chhetri, Pius Buobu, Jason Ridlon, Ece Mutlu, Vanessa Oddo, Sage J. Kim, Evgenia Karayeva, Kate Mackie, Chris Greening, Caitlin Welsh, H. Rex Gaskins, Lisa Tussing-Humphreys. Socioenvironmental contributors to dietary cysteine, the gut microbiome, and CRC disparities [abstract]. In: Proceedings of the 18th AACR Conference on the Science of Cancer Health Disparities; 2025 Sep 18-21; Baltimore, MD. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2025;34(9 Suppl):Abstract nr A066.