Abstract B12: Cross-sectional analysis of grain, gluten, and fiber intakes and gut microbiota in the Food and Microbiome Longitudinal Investigation (FAMiLI) Study

Whole grains are recommended as part of a healthy dietary pattern for the prevention of chronic diseases, including colorectal cancer. Greater whole grain consumption may beneficially alter gut microbiota, and it is unclear if gluten, a protein component of grains, is also associated with altered microbiota. To examine the association between grain, gluten, and fiber intake with gut microbiota, we analyzed data from the ongoing prospective Food and Microbiome Longitudinal Investigation Study. This cross-sectional analysis included 300 men and 501 women of White, Black, Hispanic, and Asian race/ethnicity who completed a 137-item semiquantitative food frequency questionnaire. Gluten intake was estimated using the protein content of grain products. Bacterial 16S rRNA genes from stool samples collected via RNAlater tubes were amplified, sequenced, and assigned to bacterial taxa. We examined associations of whole and refined grain, gluten, and dietary fiber intakes with gut microbiota diversity and composition using multivariable-adjusted linear regression models and permutational multivariate analysis of variance, respectively, and with microbial taxa abundance using analysis of composition of microbiomes (ANCOM). In this diverse study population, the highest quartiles of energy-adjusted refined grain and gluten intake, when compared to the lowest quartiles, were associated with lower Shannon diversity (P-trend=0.03 and P-trend=0.01, respectively), but no other associations with alpha- or beta-diversity measures were observed. The highest quartile of dietary fiber was not associated with alpha-diversity measures but was associated with shifts in overall gut microbial composition (P-trend=0.02). Whole grain intake was not statistically significantly associated with these microbiome parameters. However, the highest quartile of whole grain intake, compared to the lowest quartile, was associated with greater abundance of several gut taxa, including classes Erysipelotrichi (family Erysipelotrichaceae), Clostridia (genus Faecalibacterium and Lachnospira), and Bacteroidia (Bacteroides plebeius). Higher whole grain intake was also associated with lower abundance of classes Bacteroidia (family Rikenellaceae and Bacteroides uniformis) and Clostridia (genus Oscillospira and Ruminococcus). Similarly, the highest quartile of dietary fiber intake was associated with greater abundance of classes Erysipelotrichi (family Erysipelotrichaceae) and Clostridia (genus Lachnospira) and lower abundance of class Bacteroidia (family Rikenellaceae). Higher intakes of refined grain and gluten were not statistically significantly associated with altered abundance of gut taxa. Though this study is cross-sectional, identification of gut microbes associated with higher intakes of whole grain and fiber may expand our understanding of how these nutritional factors lower risk for colorectal cancer. Citation Format: Caroline Y. Um, Brandilyn A. Peters, Emilia N. Cobbs, Hee Sun Choi, Dia B. Beggs, Richard B. Hayes, Marjorie L. McCullough, Susan M. Gapstur, Jiyoung Ahn. Cross-sectional analysis of grain, gluten, and fiber intakes and gut microbiota in the Food and Microbiome Longitudinal Investigation (FAMiLI) Study [abstract]. In: Proceedings of the AACR Special Conference on the Microbiome, Viruses, and Cancer; 2020 Feb 21-24; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2020;80(8 Suppl):Abstract nr B12.