Nutrient intakes were assessed using 24-hour dietary
recall, a food frequency questionnaire (FFQ), and a food
change questionnaire (FC). The 24-hour dietary recall was
obtained by research dietitians, and nutrient intakes from
the dietary recalls were calculated using a computerized
food analysis system (SY Software, developed in the
School of Public Health, Fudan University, Shanghai,
China). Additional information about participants’ food
choices was obtained using FFQ and FC questionnaires
which were developed by experienced nutritionists from
the Clinic Nutrition Center at Fudan University based on
Chinese food habits and validated based on frequently
used food in the Shanghai area.13 For simplicity, the FFQ
included a list of 18 common foods and beverage categories,
including over 150 individual food items. For example,
selections for rice frequency were: “3 times per day,”
“2 times per day,” “once a day”, “every other day,” “and
1 to 2 times a week.” The unit of intake was “liang” (one
liang = 50 grams). For the FC questionnaire, participants
indicated the changes of main food intake from beginning
to end of the study; participants were asked to compare
their current diet to that before they enrolled by marking
“increase” “decrease” or “no change” for 17 food category/
preparation choices. Change amount was required to
be at least 1 serving increase or decrease daily. Many of
the food categories for the FFQ and FC differed between
questionnaires making comparisons difficult; therefore,
these data are used for descriptive qualitative purposes
and not for survey cross-validation.