Abstract A26: Diet quality vs quantity in relation to the fecal microbiome among colonoscopy patients

Diet remains a promising target with the potential to impact colorectal cancer risk via the balance of energy and body weight, as well via specific food components with known anti-carcinogenic properties. Growing evidence implicates the importance of the gut microbiome in the interaction of diet, energy balance, and inflammation—key mechanisms associated with colorectal cancer development. The tight coupling of diet and the gut microbiota may hold new answers for colorectal cancer prevention. Methods: We conducted a pilot epidemiologic study among 50 cancer-free MD Anderson colonoscopy patients with no underlying familial/genetic or chronic inflammatory bowel conditions. With the overall goal to identify dietary intervention targets in obese and lean individuals at varied risk of colorectal neoplasia, patients provided fasting blood at colonoscopy, stool samples via mail ~ 1 month post-polypectomy, and comprehensive dietary assessments. Total energy intake was derived from responses to both the Diet History (DH) and 24-hour dietary recalls (24HR) and diet quality was defined by the Healthy Eating Index (HEI). We conducted 16S rRNA gene sequencing of the fecal microbiota and measured circulating blood adipocytokines via Luminex multiplex assays (Millipore). Results: Majority of colonoscopy patients recruited into the study were female (67%) and diagnosed with precancerous colorectal polyps (57%), primarily tubular and sessile serrated adenomas. Patients with precancerous polyps removed at colonoscopy were more likely to be obese than patients without precancerous polyps, but otherwise similar by age, macronutrient composition, and HEI. Differences in the overall composition of the fecal microbiome via weighted and unweighted unifrac were observed by reason for colonoscopy (symptomatic vs asymptomatic screening), chronic medication use (yes vs. no), total energy and alcohol intake (tertiles); and effects of each these factors were considered in subsequent analyses. No differences were observed by other clinicopathologic features, demographics, or lifestyle factors. High total energy intake was significantly correlated with higher alpha diversity of the fecal microbiome. This linear relationship remained following adjustment for diet quality and was consistent across colonoscopy status, BMI, medication use and alcohol intake (FDR-adj P