Methodological issues in the identification of dietary patterns in nutritional epidemiology : report from a review on breast cancer

Because of the complexity of diet and the potential for interaction between dietary components, approaches that focus on individual foods or nutrients may miss information on the role of diet in disease etiology. Due to their ability to capture the variation in overall food intake in a given population, dietary patterns (multiple dietary components operationalized as a single exposure) have been used to describe associations between diet and disease. By characterizing a healthy diet in a current population, they also allow for dissemination of dietary recommendations in a practical way. Dietary patterns might, therefore, be considered a valuable alternative to single food/nutrient approaches, giving contributions to both risk factor definition and disease prevention. Available information on dietary patterns and cancer is still sparse. Moreover, although the body of literature has recently increased, a meaningful assessment of the association between dietary patterns and cancer still requires to refine the statistical techniques and to address the issue of reproducibility of dietary patterns. We present results from a review of papers published to date that have identified dietary patterns according to all the existing approaches and have assessed the association with breast cancer. Since 1995, we identified 19 papers based on studies conducted in various populations across many countries. The majority of them identified a posteriori dietary patterns, mainly using principal component factor analysis. Six papers did not find any association between the identified dietary patterns and breast cancer. Nine papers identified 1 dietary pattern significantly associated with breast cancer, and the remaining 4 identified 2 to 4 dietary patterns related to breast cancer.