Dietary Inflammatory Index and Renal Cell Carcinoma Risk in an Italian Case–Control Study

Background: The relation between diet-related inflammation and renal cell carcinoma (RCC) has not been investigated. Methods: In this study, we explored the association between the dietary inflammatory index (DII) and RCC in an Italian case–control study conducted between 1992 and 2004. Cases were 767 patients with incident, histologically confirmed RCC. Controls were 1534 subjects admitted to the same hospitals as cases for various acute, nonneoplastic conditions. The DII was computed based on dietary intake assessed using a reproducible and valid 78-item food frequency questionnaire. Odds ratios (ORs) were estimated through logistic regression models conditioned on age, sex, and center, and adjusted for recognized confounding factors, including total energy intake. Results: Subjects in the highest quartile of DII scores (i.e., with the most proinflammatory diets) had a higher risk of RCC compared to subjects in the lowest quartile [OR 1.41, 95% confidence interval (CI) 1.02, 1.97; p-trend = 0.04)]. Apparently stronger associations were observed among females (OR 1.68, 95% CI 0.93, 3.03), subjects aged <60 yr (OR 1.77, 95% CI 1.05, 2.98), body mass index ≥25 kg/m² (OR 1.64, 95% CI 1.07, 2.51), and ever smokers (OR 1.66, 95% CI 1.08, 2.57), in the absence of significant heterogeneity. Conclusion: A proinflammatory diet is associated with increased RCC risk.