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

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.

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 (n = 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.

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_adjusted = 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_adjusted = 1.01, 95% CI: 0.80, 1.26).

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.