Diet in the Italian EPIC cohorts: presentation of data and methodological issues

One of the aims of the EPIC study is to produce accurate descriptions of the dietary habits of the participants recruited in the 27 EPIC centers of 10 European countries. To do this, different dietary assessment instruments were developed and applied to capture the wide range of diets characterizing the different European populations. Three different food frequency questionnaires were developed for Italy: one for the centers of Varese, Turin and Florence, one for Ragusa and one for Naples. These inquired about eating habits over the previous year and were completed by 46,839 Italian EPIC participants. Specially developed software analyzed the responses and linked them to food composition tables in order to provide a nutritional breakdown of individual and collective diets. A further aim of EPIC was to develop a method of rendering data from different dietary questionnaires comparable. To do this, dietary data were collected from a sample of about 8% of the Italian EPIC cohort, using a standardized computer-driven 24-hour dietary recall interview, and then compared with the dietary data collected by the questionnaires. This paper provides an extensive description of the technical features and performance of the food frequency questionnaires and the 24-hour recall interview, including a comparison of estimates of the intake of different food groups provided by the two instruments. From this comparison, the repeatability and reliability of consumption estimates was assessed, resulting in indications for improving data comparability. The paper also presents food frequency questionnaire estimates of the daily intake of foods and nutrients by center, sex and age group, as well as information on dietary habits such as place and time of intake, and food preparation and preservation methods as provided by the 24-hour recall interview. The picture that emerged is that Italian eating habits are undergoing marked changes, with a tendency to less healthy eating. Documentation of these changes in relation to age, sex and region provides an essential starting point for investigating the influence of diet on the development of cancer and other chronic diseases.