Abstract
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.