Usual dietary intake was assessed by centrally trained interviewers using a 1-year semiquantitative 114-item food frequency questionnaire (18) ascertaining both frequency and serving size. Servings per day were converted to the medium size (19). We created 33 food groups on the basis of similarities in food and nutrient composition (19). Alcoholic beverage consumption was queried separately. Daily nutrient and energy intake was estimated from the food frequency questionnaire and the alcohol questionnaire using an expanded nutrient database (HHHQ-D1ETSYS analysis software, version 3.0; National Cancer Institute, Bethesda, MD). A structured interview was used to collect 1-year recall of physical activity from which total energy expenditure was estimated. Family history of diabetes, smoking, and race/ethnicity were self- reported.
Statistical analysis