The Second National Nutrition Survey (1982): The data collection method included dietary interview, blood and urine test, and medical examination (5,8).
The Third National Nutrition Survey (1992): The survey collected the data by dietary interview, hemoglobin test, and medical examination (1,8).
China National Nutrition and Health Survey (2002): The methods to obtain the information included interview, dietary, lab test, and body measurement (3,8).
China Nutrition and Health Surveillance (2010–2013): The data collection used interviews, dietary interview, lab test, and body measurement (4,7).
China Nutrition and Health Surveillance (2015–2017): The 2015–2017 survey collected the used interviews, anthropometric measurements, dietary survey, and laboratory tests.
The interviews included household or individual questions such as for information related to demographics, economics, smoking, alcohol consumption, physical activities, health-related question, family disease history, health insurance, early development and milestones (infant), etc. Questionnaires designed by the China CDC project team were used and completed by strictly trained field workers in face-to-face interviews in households or at local fixed sites.
The anthropometric measurements were conducted by trained local CDC staff and consisted of weight, height, length, head circumference, waist circumference, and blood pressure. All equipment was selected by the national project team. Body weight was measured using electric scale (TANITA, HD-390) with accuracy up to 0.01 kg. Length of children under 2 years was measured using infant scale with accuracy up to 0.1 cm. Height was measured using a stadiometer with accuracy up to 0.1 cm. The head measuring tape checked children’s head circumference. The soft tape was used to measure waist circumference. Blood pressure measurements used Omron HBP 1300 electronic sphygmomanometer. The equipment was calibrated before physical examination in the local fixed site or when the equipment was moved.
Three dietary survey methods were used in 2015–2017. 1) 3 consecutive days food weight record (2 weekdays and 1 weekend day): interviewers weighed and recorded the amounts of edible oils, salt, sauce, and other flavorings in the household before and after the 3-day survey. 2) 3 consecutive days 24-hour dietary recall (2 weekdays and 1 weekend day): interviewers collected food intake information for 3 days for individuals during a 24-hour period, including breakfast, lunch, dinner, soft beverages, wine, snacks, dietary supplements, other foods that consumed in or away the home except edible oils, water or energy-free water, soups, and flavorings. 3) Food Frequency Questionnaire (FFQ): an FFQ interview was conducted by interviewers using a foods list to collect the consumption frequency and amount in the past 12 months. Parts of participants finished the three days’ food weight record and 24-hour dietary recall, and all participants finished FFQ. The dietary survey was personally conducted in households or at local fixed sites.
Laboratory sample collecting and tests were administered by highly trained medical personnel. In 2015, all adults were drew 8 mL of fasting venous blood and test blood biochemical and nutritional indicators (blood glucose, blood lipids, vitamin A, vitamin D, serum ferritin, etc.). In 2016–2017, fingertip blood was collected in children aged 0–5 years to detect hemoglobin; 30 children aged 3–5 years (4 mL sample), all children and adolescents aged 6–17 years (6 mL sample), and lactating women (6 mL sample) in each survey site had fasting venous blood drawn and were tested for biochemical and nutritional indicators. Hemoglobin concentration was tested using Hemocue in the field. Some participants had 24-hour urine or random urine tests collected to detect urine sodium and iodine, etc.
The protocols of China Adult Chronic Disease and Nutrition Surveillance (2015) and China Nutrition and Health Surveillance of Children and Lactating Women (2016–2017) were approved by the Ethical Committee of China CDC. Ethical approval numbers were 201519 and 201614, respectively. The participants were included in the survey only after they signed informed consent forms.