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Towards a harmonised Total Diet Study approach: a guidance document
Food and Agriculture Organization of the United Nations (FAO), Rome, Italy World Health Organization (WHO), Geneva, Switzerland
A Total Diet Study (TDS) can be a complementary approach to traditional monitoring and surveillance programs, which instead of focusing on compliance is designed to provide a solid basis for calculating population dietary exposure and assessing potential impact on public health. A TDS includes the selection of foods based on food consumption data to represent a large portion of a typical diet, their preparation to food as consumed and the subsequent pooling of related foods before analysis. There is already a wealth of international TDS data available, but to better enable comparisons it is important that methods are harmonised to the extent possible. The Working Group of experts provides a definition of the TDS approach highlighting its inherent value; it gives guidance for a harmonised methodology starting from the TDS planning to the collection of analytical results, exposure assessment calculation and communication of TDS results; and it proposes a general approach to facilitate the use of TDS information at international level. A TDS can be used for screening purposes or as a more refined exposure assessment tool. It provides background concentration and exposure levels of chemical substances in a range of representative foods prepared for consumption, while monitoring and surveillance programs can better capture highly contaminated individual food items. Their complementarities would allow the identification of the relative importance of individual sources of chemical substances from the whole diet. In conclusion, a TDS is considered to be a good complement to existing food monitoring or surveillance programs to estimate population dietary exposure to beneficial and harmful chemical substances across the entire diet. Harmonising the TDS methodology will enhance the value of these programs by improving the comparability at international level.
© EFSA, FAO and WHO, 2011
There is a need to improve the efficiency and accuracy of dietary exposure assessments for chemicalsubstances and to harmonise the collection of the data that are necessary to conduct such assessments. Data derived from the food control systems are often not suitable for calculating population dietary exposure because the sampling is targeted, the samples analysed may not be representative of the food as consumed, and the analytical method may use a too high limit of detection or quantification (LOD or LOQ).
A TDS can be a complementary public health tool to determine population dietary exposure to both beneficial and harmful chemical substances across the entire diet by analysing main foods prepared as consumed and pooled into representative food groups. Steps characterising a TDS include the selection of foods based on food consumption data to represent as best as possible a typical diet, their preparation to food as consumed and the subsequent pooling of related foods before analysis. There is already a wealth of international TDS data available that have served as important resources for monitoring exposure to beneficial and harmful chemical substances in food. To better enable comparisons of TDSs results between different surveys, it is important that methods used are harmonised to the best extent possible.
At the beginning of 2010, a Working Group (WG) of experts on TDS was formed aiming at reviewing the state of the art on TDSs worldwide with a particular emphasis on activities in Europe and at developing a guidance document for a harmonised approach of TDS.
The result of the work of the WG is provided in the current document. This guidance describes the TDS concept and highlights its inherent value; it gives principles on TDS methodology from the TDS planning to the collection of analytical results, exposure assessment and communication of TDS results with the overall objective of proposing a general approach to facilitate the use of the TDS information either internationally or at European level.
There are two distinct approaches: TDS for screening or TDS for refined dietary exposure assessment. A TDS is sometimes used for screening purposes, analysing a limited number of broadly pooled food samples. This might be useful as a starting point towards setting future priorities for more detailed collections of data on beneficial and harmful substances in food. Such screening will generate an overview at fairly low cost for a limited number of food groups. Countries that already have established monitoring or surveillance programs can use the TDS approach as a more refined dietary exposure assessment tool, which includes analysis of a greater number of less pooled samples often separately covering different seasons and regions.
Using pooled samples of individual food items means that the analytical data generated represent averages of concentration data. Therefore, TDS results are best suited for calculating chronic exposure to food chemical substances and may allow the analysis of trends where the sample size is sufficiently representative. The TDS approach will provide background contamination levels in the general food supply suitable for estimating population dietary exposure, while monitoring and surveillance activities can capture more highly contaminated individual food items. Their complementarities allow the identification of the relative importance of individual sources of beneficial and harmful chemical substances through coverage of the whole diet.
It can be concluded that a TDS can be an excellent complement to existing food monitoring and surveillance activities or it can also be a stand-alone screening tool as a starting point for further analyses. Harmonising the TDS methodology will enhance the value of these programs by improving the comparability at international level.
Total Diet Study, Dietary Exposure, Contaminants, Nutrients, Harmonisation