The association between dietary inflammatory potential and risk of total and site-specific colorectal cancer: a systematic review and meta-analysis of observational studies.

In the last decades, it has been well known that low-grade inflammation plays a potential role in the pathogenesis of different cancers. The aim of this systematic review and meta-analysis of observational studies was to evaluate the association between inflammatory potential of diet measured through the Dietary Inflammatory Index (DII), Energy-adjusted DII (E-DII), Empirical Dietary Inflammatory Pattern (EDIP), the Inflammatory Score of Diet (ISD), and risk of colorectal cancer (CRC) and site-specific colon cancer. A systematic electronic search of PubMed/Medline, Scopus, the Web of Sciences and reference lists up to 21 November 2023 was performed. Data were pooled by the generic inverse variance method using random effect model. To assess the heterogeneity of included studies, the I² index was used. A total of twenty-eight original studies, comprising 2 287 836 participants, were selected to include in this meta-analysis. Pooled results showed a significant association between higher adherence to pro-inflammatory diet and increased risk of CRC (effect size (ES): 1·39; 95 % CI 1·29, 1·51; I² = 82·9 %), colon (ES: 1·40; 95 % CI 1·26, 1·55; I² = 73·3 %, P< 0·01), proximal colon (ES: 1·28; 95 % CI 1·17, 1·40; I² = 29·1 %), distal (ES: 1·50; 95 % CI 1·30, 1·74; I² = 63·5 %) and rectal (ES: 1·46; 95 % CI 1·23, 1·74; I² = 80 %). Stratified analysis by type of dietary indices noted that greater adherence to the DII, E-DII and EDIP were related to significant increase in the risk of overall CRC and site-specific colon cancers. Our results highlighted the proposed role of inflammatory potential of diet as important risk factor for CRC. Adherence to an anti-inflammatory dietary pattern should be recommended to reduce incidence of CRC, globally.