Mediterranean diet components are negatively associated with advanced colorectal polyps in a population-based case-control study

Abstract

O-022Introduction: Colorectal cancer (CRC) is common and a leading cause of cancer-related death, which develops gradually from adenomatous and serrated polyps. Established dietary risk factors for CRC include high intake of red and processed meat, alcohol and calorie-dense foods, and low intake of plant-based foods. Adherence to the Mediterranean diet has been associated with lower risk of CRC in observational population studies. Its anti-neoplastic properties are attributed to a high fiber plant-based diet, low in calorie-dense foods, and high in fish over red meat intake. However, the association between the Mediterranean diet individual and combined components, and advanced colorectal polyps is still unclear. In this study, we aimed to evaluate the association between the Mediterranean diet individual and combined components, and advanced colorectal polyps (advanced adenoma and serrated adenoma) in a population based case-control study. Method(s): A case-control study among 808 consecutive subjects aged 40-70 years, undergoing screening or diagnostic colonoscopy. Exclusion included: colectomy, high risk for CRC, severe illness, and inability to complete the study questionnaires. All participants underwent anthropometric measurements, a medical and lifestyle interview and filled a detailed semi-quantitative food frequency questionnaire (FFQ), adapted to the Israeli population and to the needs of this study. Adherence to the Mediterranean diet components was defined as consumption of vegetables and legumes, fruits, nuts and seeds, whole grains, fish, ratio of monounsaturated (MUFA) to saturated fatty acids (SFA) and poultry above the sample median, and as consumption of red meat, alcohol, and soft drinks below the sample median. Cases with advanced polyps were defined as: advanced adenoma (adenomas >10mm, with features of high-grade dysplasia or villous histology),>3 non-advanced adenomas or serrated adenomas and SA>=10mmor with HGD. Cases were compared with controls which were free of past or present polyps. Result(s): The mean number of adhered Mediterranean diet components was significantly lower among cases with advanced polyps compared to controls (4.561.9 vs. 5.161.7, P=0.03), and was significantly associated with lower odds of advanced polyps in multivariate analysis (OR=0.81, 0.73-0.90). Adherence to 1 to 4, and 5 to 10 Mediterranean diet components were negatively associated with advanced colorectal polyps compared to none (OR=0.50, 95%CI 0.32-0.79, P=0.003 and OR=0.47, 95%CI 0.26-0.83, P=0.009, respectively). The components of the Mediterranean diet which were negatively associated with advanced polyps, with adjustment for potential confounders and to all other dietary components were: low intake of soft drinks (OR=0.65, 0.44-0.97), high intake of fruit (OR=0.66, 0.45-0.95) and high intake of fish (OR=0.62, 0.42-0.91). Combined adherence to all three components was significantly associated with lower odds of advanced colorectal polyps (OR=0.14, 0.04-0.41). Conclusion(s): Adherence to the Mediterranean diet is negatively associated with advanced colorectal polyps. High intake of fish and fruit and low intake of soft drinks are associated with lower odds of advanced colorectal polyps, separately and even more so when combined. Prospective, large-scale studies may better clarify the relations between dietary pattern and colorectal neoplasia.