Dietary inflammatory index, Mediterranean diet score, and lung cancer: a prospective study

Purpose: To investigate prospectively the associations of Dietary Inflammatory Index (DII) and Mediterranean Diet Score (MDS) with lung cancer. Methods: We used data from men and women aged 40–69 years at recruitment in 1990–1994, who were participants in the Melbourne Collaborative Cohort Study (n = 35,303). A total of 403 incident lung cancer cases were identified over an average 18-year follow-up. Hazard ratios (HR) were estimated using Cox regression, adjusting for smoking status and other risk factors, with age as the time metric. Results: An inverse correlation was observed between the DII and MDS (ρ = −0.45), consistent with a higher DII being pro-inflammatory and less ‘healthy,’ while a high MDS reflects a ‘healthier’ diet. The DII was positively associated with risk of lung cancer in current smokers [HR_{Q4 vs Q1} = 1.70 (1.02, 2.82); P_trend = 0.008] (p interaction between DII quartiles and smoking status = 0.03). The MDS was inversely associated with lung cancer risk overall [HR_{7–9 vs 0–3} = 0.64 (0.45, 0.90); P_trend = 0.005] and for current smokers (HR_{7–9 vs 0–3} = 0.38 (0.19, 0.75); P_trend = 0.005) (p interaction between MDS categories and smoking status = 0.31). Conclusions: The MDS showed an inverse association with lung cancer risk, especially for current smokers. A high DII, indicating a more pro-inflammatory diet, was associated with risk of lung cancer only for current smokers. A healthy diet may reduce the risk of lung cancer, especially in smokers.