• West China School of Nursing/West China Hospital, Sichuan University, Chengdu, China.
• Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden.
• Cancer Prevention and Control Program and Department of Epidemiology and Biostatistics, Arnold School of Public Health, University of South Carolina, Columbia, SC, USA.
• West China Second Hospital, Sichuan University, Chengdu, China.
• West China School of Nursing/West China Hospital, Sichuan University, Chengdu, China. jiangxiaolianhl@163.com.

BACKGROUND: Acknowledging the role of inflammation in colorectal carcinogenesis, this study aimed to evaluate the associations between diet-associated inflammation, as measured by the energy-adjusted dietary inflammatory index (E-DII^TM), and distinct stages of colorectal carcinogenesis.

METHODS: The Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial enrolled participants without a colorectal cancer history, who were asked to complete baseline questionnaires and food frequency questionnaires. To estimate the associations between the E-DII and risks of newly incident colorectal adenoma, recurrent adenoma, and colorectal cancer, multivariable-adjusted Cox proportional hazards regression models were employed.

RESULTS: Among 101,680 participants, with an average age of 65 years, a total of 1177 incident colorectal adenoma cases, 895 recurrent adenoma cases and 1100 colorectal cancer cases were identified. Higher E-DII scores from food and supplement (HR_{Q5 vs Q1}: 0.86 [0.69-1.06], P_trend: 0.27) or from food only (HR_{Q5 vs Q1}: 0.82 [0.64-1.05], P_trend: 0.06) were not associated with higher risks of incident adenoma. However, the elevated risk of recurrent adenoma was found in the highest category of E-DII from food plus supplement (HR_{Q5 vs Q1}: 1.63 [1.28-2.03], P_trend: < 0.001) when compared with the lowest category. A significant association between colorectal cancer risk and E-DII from food plus supplement (HR_{Q5 vs Q1}: 1.34 [1.09-1.65], P_trend: 0.009) was found, where this association was only pronounced in distal colorectal cancer.

CONCLUSION: Higher E-DII scores from diet plus supplement but not from diet only were associated with a higher risk of recurrent adenoma and distal colorectal cancer. The role of nutrient supplements on cancer risk, especially when combined with diet, needs to be elucidated in future studies.