Association Between the Dietary Index for Gut Microbiota (DI-GM) and Colorectal Cancer in the PLCO Cohort.

[OBJECTIVES] The study aimed to examine the association between a dietary index for gut microbiota (DI-GM) and the risk of incident colorectal cancer (CRC). Clarifying the role of diet-induced alterations in the composition and function of gut microbiota on the development of CRC can contribute to prevention efforts.

[METHODS] Participants from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening trial enrolled in the intervention arm and who completed baseline assessments were included in the analysis ( = 55,685). The DI-GM is a literature-derived index used to score diet quality in terms of maintaining healthy gut microbiota. A time-dependent Cox model stratified by follow-up years (<5 and ≥5 person-years) was used to evaluate the relationships between the dietary patterns and risk of incident CRC.

[RESULTS] A total of 735 incident CRC were identified over 650,470 person-years of follow-up. During < 5 years of follow-up, those with higher diet quality (DI-GM scores above 67th percentile) had an 18% lower risk of incident CRC (HR = 0.82, 95% CI: 0.63, 1.07) compared with those with lower diet quality (DI-GM scores below the 67th percentile), though effect estimates were imprecise. During ≥ 5 years of follow-up, there was no association between incident CRC and DI-GM (HR = 1.01, 95% CI: 0.80, 1.26).

[CONCLUSIONS] Diet quality measured using the DI-GM was associated with the risk of CRC in the first five years of follow-up in a large prospective cohort study. A diet that enhances the composition and function of gut microbiota may contribute to reduction in CRC risk.