Meta-analysis of the association between dietary inflammatory index (DII) and cancer outcomes

Proinflammatory dietary patterns have been associated with increased cancer risk and mortality. We present a systematic review and meta-analysis of the current published literature on a dietary inflammatory index (DII) score and its association with cancer risk and mortality outcomes. Published articles from online databases (PubMed, Scopus, and Embase) examining the association between DII and any cancer risk, incidence, or mortality between 1980 and November 2016 were selected for review. Results of studies meeting inclusion criteria were summarized and meta-analyzed using STATA to generate summary measures of association across studies. Sixty-three published articles were identified from the search, and following title, abstract and full-text review, twenty-four studies met inclusion criteria. All articles calculated DII scores based on study-specific food-frequency questionnaires using methodology from the same article. Of the 24 included studies, 13 were case-control, 6 were prospective cohort, 1 was a retrospective cohort, 3 were RCTs, and 1 did not specify study design. The most common cancers examined were colorectal, breast, lung, and prostate. Individuals in the highest versus lowest DII categories had 25% increased risk of overall cancer incidence (RR: 1.25, 95% CI: 1.16-1.35), 75% higher odds of cancer (OR: 1.75, 95% CI: 1.43-2.16) and 67% increased risk of cancer mortality (RR: 1.67, 95% CI: 1.13-2.48). Upon stratification for cancer type, positive associations remained (RRbreast: RR: 1.12, 95% CI: 1.03-1.22) (RRcolorectal: 1.33, 95% CI: 1.22-1.46) (RRlung: 1.30, 95% CI: 1.13-1.50). There were consistent and significant positive associations between higher DII and cancer incidence and mortality across cancer types, study populations, and study design.