China Total Diet Study
A Total Diet Study (TDS) is recommended by the World Health Organization as an important activity for its member nations to undertake, because it has beenrecognized internationally as the most cost-effective and reliable method to estimate dietary exposures to food chemicals or intakes of nutrients for various population groups and to assess their associated health risks in a country or area.
As part of its mandate to ensure that chemicals are not present in foods at levels that would pose an unacceptable risk to health, China National Center for Food Safety Risk Assessment (CFSA) is responsible for carrying out China Total Diet Study (CTDS) to provide estimated levels of exposure to chemicals that China residents in different age-sex groups accumulate through the food supply. The role of CTDS is to provide a scientific basis for assessing food safety risks and regulating the food supply. It can also facilitate risk managers to focus their limited resources on food chemicals or nutrients that may pose the greatest risks to public health.
This type of study is a large and complex project with many components, which involves purchasing samples of food throughout China, preparing the foods as they would be consumed (table-ready), and analyzing the foods to measure the levels of selected contaminants and nutrients. Dietary intakes of these analytes by the Chinese population are then calculated by multiplying the levels found in TDS foods by the average consumption amount for each food for each age-sex group. The dietary exposure estimated is then compared to (a) the relevant health-based reference level for food chemicals of concern, such as the Provisional Tolerable Weekly Intake (PTWI) orAcceptable Daily Intake (ADI), or (b) the nutritional reference values for nutrients of concern, such as the Recommended Nutrient Intake (RNI) for assessing the associated health risks due to dietary deficiencies.
Since 1990, CTDS has been five times. The first CTDS was comprised of 4 typical diets (North 1 and 2 and South 1 and 2) and was conducted in 12 provinces (see map of sampling sites below) in 1990. This was followed by CTDS in 1992, 2000 and 2007. The 5th TDS was conducted from 2009 to 2013. All of these studies were organized by the CFSA, and are supported by provincial CDC teams.The overall strategy and goals of the CTDS have remained constant since its inception in 1990, but the specific methodology has been revised periodically. Exhaustive histories of the CTDS have been published elsewhere (see the list of publication for CTDS).
All food composites are analysed for the presence of toxic chemical and nutritionally important substances. The following summary describes the evolution of the CTDS over the years:
1st TDS (1990)composite foods, adult males only, 22 contaminants and 76 nutrients;
2nd TDS (1992)composite foods, adult males plus 4 age-sex groups, Spring and Fall and urban and rural sample collection, 25 contaminants and 50 nutrients;
3rd TDS (2000) composite foods plus individual foods, adult male + 10 age-sex groups, 30 contaminants and 19 nutrients;
4th TDS (2007) Provincial composite foods plus individual foods;
5th TDS (2009 - 2013) Enlarged to 20 provinces.
The recent 5th CTDSwas conducted in 20 provinces over the span of the survey period, which included about 5 provinces each year. Individual food items are purchased from three to four different markets in sampling sites. Food samples are sent to local provincial CDC where they are prepared and processed as they ‘would be consumed’ in the average household kitchen (i.e., raw meats are cooked; fresh vegetables cooked or properly peeled, trimmed or otherwise cleaned for serving if not cooked). These processed foods (about 2000 individual food samples in the 5th CTDS) are then mixed according to each category to make composites (there were over 12 different food composites for each provincial samples). All food composites are analyzed for the presence of toxic chemicals and nutritionally important substances.
Ingestion of excessive amounts of contaminants through the food supply can have detrimental effects on the health of consumers. It is therefore essential to analyze the foods for contaminants and other chemicals through regular monitoring and surveillance programs to assure that chemical levels found in foods remain safe and within acceptable national and international norms.
Priority chemicals that have been evaluated in the CTDS include:
1) Metals and other elementsas well as their more toxic forms, such as lead, cadmium, arsenic (including inorganic arsenic), mercury (including methyl mercury), and tin (including organic tin)
2) Emerging hazards, such as acrylamide, ethylcarbamate, chloropropanols, melamine, phthalates, and bisphenol A (BPA)
3) Persistent organic pollutants, such as dioxins/furans, polychlorinated biphenyls (PCBs), polybrominateddiphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDDs), TBBPA, and perfluorinated substances (PFAS)
4) Other potentially toxic chemicals, such as pesticides, veterinary drugs and banned chemicals.
These concentrations are then combined with food intake information (estimates of how much Chinese consume of each food group) to provide estimates of the dietary intakes of these chemicals for Chinese in the following age-sex groups:
2 - 7 years, male and female
8- 12 years, male and female
13 - 19 years, male
13 - 19 years, female
20 - 50 years, male
20 - 50 years, female
51 - 65 years, male
51 - 65 years, female
65+ years, female
65+ years, male
All ages Chinese, male and female
Dietary intake for Chinese in different age-sex groups as well as the corresponding concentration of contaminants and other chemicals in foods from CTDS carried out since 1990 have beenpublished in peer-review journals and is available as public information.