Let food be thy medicine: the role of diet in colorectal cancer: a narrative review.

Background and Objective: Colorectal cancer (CRC) is the third most common cancer worldwide, and the incidence and mortality rates continue to increase annually. Many factors, including genetic, immune, and environmental factors, influence the occurrence and development of CRC. Along with the economic development, changes in lifestyle, especially dietary factors, have been shown to greatly affect the progression of CRC. Increasing evidence showed that dietary patterns influence the risk of CRC and affect CRC treatment. The present review describes the role of diet in the prevention and treatment of CRC with the hope that doctors attach importance to dietary patterns in educating patients with CRC or at risk of CRC and that diet may be regarded as an auxiliary treatment strategy to improve patients' outcomes. Methods: English language articles published from 2000 to December 2021 in PubMed and Embase were identified by searching titles for keywords including "diet", "colorectal cancer", "dietary pattern", and "dietary factor"; 101 articles were selected for review. Key Content and Findings: The present review describes the role of different dietary patterns and factors in the prevention and treatment of CRC. We found that dietary intervention is closely related to the occurrence, development, and prognosis of CRC. Adherence to the Mediterranean diet (MD), the Dietary Approaches to Stop Hypertension (DASH) diet, fasting, vegetarian diets and the ketogenic diet (KD) were found to reduce the risk of CRC, prolong patient survival, and delay disease progression. Moderate intake of dietary fiber (DF), omega-3 fatty acids, micronutrients (e.g., calcium, iron, and selenium), and vitamins have been shown to be beneficial in the prevention and treatment of CRC. Conversely, diets high in fat or sugar and those rich in red meat or processed meat promote CRC. Conclusions: People at high risk of CRC and those with CRC are recommended to eat a plant-based diet rich in fruits, vegetables, and whole grains with appropriate DF intake and to avoid high levels of processed meat, red meat, and highly refined grains.