Diet-related inflammation and risk of prostate cancer in the California Men's Health Study

The purpose of the study was to examine the relationship between proinflammatory diet and prostate cancer risk.

Energy-adjusted Dietary Inflammatory Index (E-DII) scores were computed among 40,161 participants in the California Men's Health Study. Over 9.7 ± 3.8 years of follow-up, 2707 incident prostate cancer cases were diagnosed and categorized as low-, intermediate-, or high-risk, based on disease grade and stage. Accelerated failure-time models assessed time to diagnosis of prostate cancer. Cox proportional hazard models estimated hazard ratios (HR) and 95% confidence intervals (95% CI). Nonlinear effects of E-DII were modeled as third-order polynomials.

Time to prostate cancer diagnosis did not differ by E-DII quartile. The HR for high-risk prostate cancer increased in the third E-DII quartile (HR_{Q3 vs. Q1} = 1.36; 95% CI: 1.04-1.76), but not in the fourth (HR_{Q4 vs. Q1} = 0.99; 95% CI: 0.74-1.32, P_trend = .74), suggesting a nonlinear dose-response. HR curves for prostate cancer increased exponentially above an E-DII threshold of ≈+3.0. HR curves for high-risk prostate cancer had a much steeper incline above an E-DII threshold of ≈+2.5. Curves were higher among Blacks and Whites relative to other races and among overweight or obese men. No relationship was observed between E-DII scores and intermediate- or low-risk disease.

Relationships between proinflammatory diet and prostate cancer risk may be nonlinear, with an increased risk above an E-DII threshold of ≈+2.5.