Methodological issues in epidemiological studies of diet and cancer

We review the goals of epidemiological nutritional studies and evaluate methods of dietary data collection in terms of these goals. Special problems for the cancer epidemiologist studying diet are then reviewed, including methods of data collection, quantification of food intake, and analysis of nutritional data. Food frequency methods are generally best for collection of dietary data in epidemiological studies, and the use of food data banks enables the study of specific dietary components. The major problems in analysis stem from the complex interrelationships among nutrients and their high correlation with each other.