Trained dietitians collected dietary data using a validated semi-quantitative food frequency questionnaire (FFQ) which assessed dietary intakes of cases one year before diagnosis and controls 1 year before interview. The FFQ consisted of 125 food items, including some of the most common Iranian meal recipes and has been previously shown to be valid and reproducible for use in Iranian adults (10,11). Consumption frequency was asked on a daily (e.g. bread), weekly (e.g. rice or meat) or monthly (e.g. fish) basis, and data from the questionnaire were transformed into the average monthly intake based on the assumption that each month is 30.5 days. For identifying the dietary patterns, 125 food items were grouped into 29 main food groups.