Dietary Patterns and Major Chronic Diseases

Abstract

Dietary improvement may lower the risk of developing chronic diseases and associated mortality. Despite the existence of several disease-oriented dietary recommendations, the superior diets for general health and specific disease such as colorectal cancer have not been determined. In addition, it is unknown whether and how risk factors including dietary factors influence the malignant transformation and metastasis of colorectal cancer prior to diagnosis. We attempted to address these questions using data from the Nurses’ Health Study, NHS II, and Health Professionals Follow-up Study.

In Chapter 1, we comprehensively examined the associations of 17 dietary patterns with the risk of colorectal cancer. Our results suggest that colorectal cancer was most strongly associated with diets reflecting hyperinsulinemia, chronic inflammation, Western style, and adherence to the Dietary Approaches to Stop Hypertension. These diets demonstrated independent associations with colorectal cancer after adjusting for the dietary score based on the World Cancer Research Fund/American Institute of Cancer Research recommendations, indicating that dietary recommendations can be further optimized to maximize their effects in preventing colorectal cancer.

In Chapter 2, we assessed two mechanism-based diets and six diets based on dietary recommendations for major chronic diseases. We found that maintaining a healthy diet was generally associated with a decreased risk of major chronic disease, defined as a composite outcome of major cardiovascular disease, type 2 diabetes, and cancer. Among the eight dietary patterns examined in this study, those reflecting low insulinemic, low inflammatory, and diabetes risk reduction diet may confer the largest risk reduction for various chronic diseases. These findings suggest that diets implicated in insulin and inflammation pathways may guide future dietary guidelines to optimize the health benefits of dietary modification

In Chapter 3, we investigated the associations of 34 prediagnostic risk factors with lethal colorectal cancer, defined as tumors at stage IV at diagnosis or caused cancer-associated death within five years of diagnosis. Our findings suggest several dietary and lifestyle factors may be targeted early before diagnosis to reduce CRC mortality in addition to CRC incidence, such as coffee, whole grains, and cereal fiber. The differential associations with lethal endpoints for age, height, a history of lower gastrointestinal endoscopies, and a diet reflecting chronic inflammation provide evidence of etiologic heterogeneity in malignant potential. The lower proportion of distal colon cancer, and higher proportion of non-MSI-high, and KRAS-mutated tumors in lethal cases suggest that the aggressive phenotypes may be reflected in the tumor at diagnosis.