Meta-analysis of the association between the inflammatory potential of diet and colorectal cancer risk

Objectives: The inflammatory potential of diet has been inconsistently linked to colorectal cancer (CRC) risk. This meta-analysis aimed to evaluate the association of the inflammatory potential of diet, as estimated by the dietary inflammatory index (DII) score, with CRC risk.

Materials and methods: The PubMed and Embase databases were searched for relevant studies from inception to February 2017. All cohort and case-control studies investigating the association of the DII score with CRC risk were selected.

Results: Four prospective cohorts and four case-control studies, which enrolled a total of 880,380 participants, were included. The pooled adjusted risk ratio (RR) of CRC for the highest DII score versus the lowest category was 1.43 (95% confidence interval [CI]: 1.26-1.62). When stratified by study design, the RRs for the case-control and cohort studies were 1.27 (95% CI: 1.16-1.38) and 1.81 (95% CI: 1.48-2.22), respectively. Subgroup analysis showed that individuals with the highest category of DII score were independently associated with CRC risk in men (RR=1.51; 95% CI: 1.29-1.76), women (RR=1.25; 95% CI: 1.10-1.41), colon cancer (RR=1.39; 95% CI: 1.19-1.62), and rectal cancer (RR=1.32; 95% CI: 1.01-1.74). However, the pooled RR was 1.07 (95% CI: 0.87-1.31) for rectal cancer among the prospective cohort studies.

Conclusions: As estimated by a high DII score, pro-inflammatory diet is independently associated with increased CRC risk. This finding confirms that low inflammatory potential diet may reduce CRC risk. However, the gender- and cancer site-specific associations of the DII score with CRC risk need to be further investigated.