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.