The CKB study administered a qualitative FFQ at baseline (2004–2008) and the first resurvey (2008–2009) and then switched to a quantitative FFQ in the second resurvey (2013).
The short qualitative FFQ chose 12 food items, including rice, wheat products, other staple foods (millet, corn, etc.), meat, poultry, fish/seafood, eggs, fresh vegetables, fresh fruit, dairy products, preserved vegetables, and dairy products according to recommendations from the Chinese Dietary Guidelines. Five frequency options were never or rarely, monthly, 1–3 days/week, 4–6 days/week, and daily.
The quantitative FFQ retained the first nine food items in the qualitative FFQ and split the remaining three items into two or three subgroups (Supplementary Table S1 ). In addition, four new items were added, including pure fruit/vegetable juice, dried vegetables, carbonated soft drinks and other cold soft drinks. Alternative frequency levels remained the same as the qualitative FFQ. Participants estimated the average amount assisted by colour plates picturing the usual size and weight of food items.
The short qualitative FFQ chose 12 food items, including rice, wheat products, other staple foods (millet, corn, etc.), meat, poultry, fish/seafood, eggs, fresh vegetables, fresh fruit, dairy products, preserved vegetables, and dairy products according to recommendations from the Chinese Dietary Guidelines. Five frequency options were never or rarely, monthly, 1–3 days/week, 4–6 days/week, and daily.
The quantitative FFQ retained the first nine food items in the qualitative FFQ and split the remaining three items into two or three subgroups (
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