Association between the dietary inflammatory index and the incidence of cancer: a systematic review and meta-analysis of prospective studies

Objective: Although many risk factors for cancers have been well defined, the effects of dietary inflammation have remained controversial. We aimed to summarize the association between the dietary inflammatory index (DII) and the risk of cancer. Study design: A systematic review and meta-analysis on prospective studies. Methods: Electronic databases including PubMed/MEDLINE, Scopus, and Web of Science were searched to find relevant articles published in English up to February 2017. Prospective studies that reported the relative risk (RR) or hazard ratio for the most pro-inflammatory vs the most anti-inflammatory diets and cancer were included. Random effects model was used to pool the effect sizes. Results: Finally, 11 effect sizes from 10 prospective studies were included. Findings indicated that the most pro-inflammatory vs the most anti-inflammatory diets were significantly associated with an increased risk for total cancer (overall RR: 1.17; 95% confidence interval [CI]: 1.09-1.26) with a substantial heterogeneity (I-2: 85.5%, P < 0.001). Subgroup analysis revealed that the association between DII and breast cancer was 1.04 (95% CI: 1.02, 1.07; I-2: 0%; P = 0.66), while it was 1.26 (95% CI: 1.17, 1.36; I-2 = 58.1%; P = 0.03) for colorectal cancer. Conclusions: Although the findings of the current meta-analysis support the hypothesis that diets with high pro-inflammatory components can increase the risk of cancer, the heterogeneity was high. Therefore, further studies are required to clarify this association. (C) 2018 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.