Joint EFSA, FAO and WHO guidance aims to harmonise dietary exposure assessments
The European Food Safety Authority (EFSA), the Food and Agriculture Organisation of the United Nations (FAO) and the World Health Organisation (WHO) have published jointly guidance for a harmonised Total Diet Study (TDS) approach. The organisations conclude that, together with other dietary surveillance programmes, TDS is an effective tool to estimate population dietary exposure to both harmful and beneficial chemicals across the overall diet. The guidance proposes general principles for harmonising TDS methods internationally, which if applied in Europe would provide comparable data on dietary exposure to chemicals in food.
Reliable and detailed data on the occurrence of chemical substances (e.g. nutrients, residues, contaminants[1]) in food in combination with food consumption data are essential for exposure assessments to support scientific advice on potential risks in the food chain. The chemical occurrence data used are often derived from official food controls, whereas the overall assessments of population dietary exposure to chemicals requires representative and harmonised data collection. A working group involving representatives from EFSA, FAO, WHO and EU Member State has reviewed the state of the art and prepared joint guidance for a method suitable for such exposure assessments: the Total Diet Study (TDS) approach. The guidance provides principles for carrying out a study, including the planning phase, collection of results, exposure assessment calculation and communication on the results.
A TDS consists of selecting and collecting foods representing the overall diet of a population, which are prepared as they are consumed and pooled into representative food groups before the levels of contaminants or nutrients in the foods are analysed. The results are then combined with food consumption data. This allows scientists to calculate the amount of each chemical substance that is being consumed by a specific population as part of their typical diet. The approach is particularly suitable for estimating chronic dietary exposure[2]. It is most efficient for estimating broadly occurring chemical substances and less appropriate for detecting chemicals that occur only regionally, seasonally or in specific foods.
While food monitoring and surveillance activities capture presence of chemicals in individual food items, TDS provides a basis for calculating overall levels of chemical substances in the foods consumed by a population and estimating the overall impact on public health. The working group concludes that TDS can be an excellent complementary approach to existing food monitoring and surveillance programmes or an effective preliminary screening tool. Together these approaches can help experts to identify the relative importance of individual foods as sources of chemical substances in the overall diet. TDS can also be used for screening purposes to analyse a limited number of broadly pooled food samples, providing a useful starting point for determining future priorities for detailed data collection.
TDSs are conducted by several countries[3] and there is a wealth of data available. However, harmonisation of the TDS methodology would enable comparability of results internationally and support the assessment of dietary exposure to chemical substances in multiple countries or regions. At European level, TDS would generate important information on pan-European dietary exposure to chemicals in food and could be used for tracking the impact of EU measures over time.
In the coming years, the European Commission´s Directorate-General for Research and Development will fund a Pan-European pilot project to harmonise data collection, identify typical foods in the overall diet and assess the dietary intake of chemical contaminants from these foods.
In January 2010, a working group was formed with representatives from EFSA, FAO, WHO and EU Member States to review the state of the art in the Total Diet Study approach worldwide with a particular emphasis on activities in Europe and to develop a guidance document for a harmonised approach for TDS.
A Total Diet Study (TDS) consists of selecting, collecting and analysing commonly consumed food purchased at retail level, processing the food as for consumption, pooling the prepared food items into representative food groups and analysing them for harmful and/or beneficial chemical substances. TDSs are designed to cover the whole diet and to measure the amount of each chemical substance of interest ingested by the population living in a country over their lifetime, using low-level, average, and high-level consumption data as appropriate for the substances being assessed.
[1] Most chemical substances in food might be grouped into one of the following areas:
• chemical substances intentionally added to foods (e.g. preservatives and colours);
• chemical residues of substances deliberately applied at other points in the food production chain (e.g. pesticides and veterinary drug residues);
• contaminants from the environment (e.g. heavy metals and dioxins);
• naturally occurring contaminants (e.g. mycotoxins and alkaloids);
• contaminants formed during food processing (e.g. furans and acrylamide) and transferred from food packaging or food contact materials (e.g. phthalates and bisphenol A);
• nutrients considered beneficial or essential (e.g. micronutrients such as vitamins and iron).
[2] Average daily exposure over the entire lifetime (World Health Organisation).
[3] By early 2011, at least 33 countries in the world had been engaged in the process of performing TDSs.
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