Dietary predictors of colorectal adenoma in different racial subgroups using three different methods of dietary evaluation
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Background: A colorectal adenoma (CRA) is a benign tumor of the inner lining of the colon or rectum that may progress to cancer. A serious concern is that there are notable racial disparities in the incidence of colorectal cancer and likely in the incidence of colorectal adenomas. It is estimated that between 40-70% of colorectal cancer cases can be attributed to diet. Considering the similarities between colorectal cancer and CRA, it seems likely that diet has an important role in the development of CRA, and differences in diet may be a contributing factor to racial disparities in CRA prevalence. Methods: Several approaches to determining the healthiness of diet (alternate Mediterranean diet index (altMED), Dietary Inflammatory Index (DII), and data-driven methods, such as factor analysis and classification and regression tree (CART) analysis) were used to determine whether or not differences in dietary intake were associated with colorectal adenoma prevalence in the different racial subgroups in the screening arm participants enrolled in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Baseline dietary questionnaires were used to characterize diet. Results: Results from logistic regression indicate that higher (more favorable) scores on the altMED index were associated with lower odds of CRA in men. In stratified analysis, black and white men had significantly lower odds of CRA with a more Mediterranean-like diet. Lower (less inflammatory) DII scores were associated with lower odds of CRA in men, compared to those with higher (more inflammatory) scores, specifically in white men. The odds of CRA was lower in men who had lower scores on the “Western” diet (consisting of meats and processed grains). This was true for all races but was only significant among white men. Higher scores on the “Fruits and vegetable” diet were not associated with CRA prevalence. Conclusion: In racially-stratified models, the altMED diet was most strongly associated with CRA prevalence in black men. Future work should focus on ways to increase the access and availability of healthy foods to high-risk populations as a primary preventive measure for reducing CRA disparities.