A harmonised approach for identifying core foods for total diet studies

Total diet studies (TDS) are used to gather information on chemical substances in food, thereby facilitating risk assessments and health monitoring. Candidate foods for inclusion in a TDS should represent a large part of a typical diet to estimate accurately the exposure of a population and/or specific population groups. There are currently no harmonised guidelines for the selection of foods in a TDS, and so the aim of this study was to explore the possibility of generating a harmonised approach to be used across Europe. Summary statistics data from the European Food Safety Authority’s (EFSA) Comprehensive Food Consumption Database were used in this research, which provided data from national food consumption surveys in Europe. The chosen methodology for the selection of foods was based on the weight of food consumed and consumer rate. Using the available data, 59 TDS food lists were created, representing over 51 000 people across 17 countries and seven population groups. All TDS food lists represented > 85% of the populations’ diets (85.9–96.3%), while the number of foods in the TDS food lists ranged from 15 to 102. Comparison of the TDS food lists indicated that the most commonly consumed foods included wheat bread and rolls, pastries and cakes, tomatoes, apples, bananas, and chicken, while cow’s milk, tap water and orange juice were the most commonly consumed beverages across Europe. This work was complete to support EFSA and other institutions in the development of harmonised TDS into the future.     

Establishing a food list for a Total Diet Study: how does food consumption of specific subpopulations need to be considered?

A Total Diet Study (TDS) consists of selecting, collecting and analysing commonly consumed foods to obtain concentration data of different chemical compounds in foods as eaten. A TDS food list summarises the most consumed foods and represents the dietary habits of the general population of the country under study. The work reported here investigated whether TDS food lists that were initially designed for the whole population of the country under study also sufficiently cover the dietary pattern of specific subpopulations that are extra vulnerable for certain contaminants. The work was performed using data of three European countries: the Czech Republic, France and the UK. Each national food consumption database was combined with the corresponding national TDS food list (containing 336, 212 and 119 food items for the Czech Republic, France and the UK, respectively). The data were aggregated on the highest level of hierarchy of FoodEx-1, a pan-European food classification system, including 20 main FoodEx-1 groups. For the group ‘milk and dairy products’, the coverage of the consumption by the food list was investigated for more refined subgroups. For each food group or subgroup and country, the average percentage of coverage of the diet by the national TDS food list was calculated for different subpopulations, including children versus adults, women versus men, vegetarians versus non-vegetarians, and women of child-bearing age versus older women. The average diet of the different subpopulations was sufficiently covered by the food list of the Czech Republic and France. For the UK the average coverage was low due to a different food-coding approach and because food lists were not derived directly from national food consumption data. At the level of the 20 main food groups, differences between the subpopulations with respect to the average coverage of consumption by the TDS food list were minimal. The differences were more pronounced when looking in detail at the coverage of the dairy consumption. TDS food lists based on the mean consumption of the general population are also applicable to study the chemical exposure of different subpopulations, e.g. children, women of child-bearing age and vegetarians. This lowers the effort when performing a TDS.     

Core food of the French food supply: second Total Diet Study

As first described in the 1980s, the core food intake model allows a precise assessment of dietary nutrient intake and dietary exposure to contaminants insofar as it reflects the eating habits of a target population and covers the most important foods in terms of consumption, selected nutrient and contaminant contribution. This model has been used to set up the sampling strategy of the second French Total Diet Study (TDS) with the aim of obtaining a realistic panorama of nutrient intakes and contaminant exposure for the whole population, useful for quantitative risk assessment. Data on consumption trends and eating habits from the second French individual food consumption survey (INCA2) as well as data from a 2004 purchase panel of French households (SECODIP) were used to identify the core foods to be sampled. A total of 116 core foods on a national scale and 70 core foods on a regional scale were selected according to (1) the consumption data for adults and children, (2) their consumer rates, and (3) their high contribution to exposure to one or more contaminants of interest. Foods were collected in eight French regions (36 cities) and prepared ‘as consumed’ to be analysed for their nutritional composition and contamination levels. A total of 20 280 different food products were purchased to make up the 1352 composite samples of core foods to be analysed for additives, environmental contaminants, pesticide residues, trace elements and minerals, mycotoxins and acrylamide. The establishment of such a sampling plan is essential for effective, high-quality monitoring of dietary exposure from a public health point of view.     

Total diet studies: the identification of core foods in the United States food supply.

Some total diet studies are based on the selection and analysis of core foods in a national or regional food supply. One way to select core foods is by computerized evaluation of the daily food intakes reported by subjects participating in national food consumption surveys. The foods consumed by the population groups of concern may be aggregated into core food groups. The foods within each group may be ranked according to daily intake and weight percentage of the total diet. The food that best represents each group may then be identified as a core food, and the daily consumption levels for each food group may then be assigned to the core food representing the group. Consumption levels may be determined for the specific age-sex categories of concern. To assess the representativeness of core foods identified in this manner, the food composition database of the national survey may be used to determine nutrient intakes based on the full range of foods in the database versus nutrient intakes based on the core foods.     

Dietary intake of pesticides: State of Kuwait total diet study

The State of Kuwait conducted a total diet study (TDS) to determine the dietary intakes of selected pesticides. This paper reports the results of this study. A national food consumption survey was performed and core food lists for different population groups were established representing the total diet of the Kuwaiti population. Food items (table-ready) were purchased/prepared and analysed for their contents of organophosphate/organochlorine carbamate, benzimidazole and phenylurea pesticides according to the US FDA Pesticide Analytical Manual (PAM I). Dietary intakes of these pesticides are presented for 19 population groups, which range from infants to elderly adults. The intakes of selected population groups are compared with representative findings from the US FDA/TDS and data published from other countries. In general, the average daily intakes were well below acceptable limits, but higher than those reported from developed countries.     

A conceptual framework for the collection of food products in a Total Diet Study

A total diet study (TDS) provides representative and realistic data for assessing the dietary intake of chemicals, such as contaminants and residues, and nutrients, at a population level. Reproducing the diet through collection of customarily consumed foods and their preparation as habitually eaten is crucial to ensure representativeness, i.e., all relevant foods are included and all potential dietary sources of the substances investigated are captured. Having this in mind, a conceptual framework for building a relevant food-shopping list was developed as a research task in the European Union’s 7th Framework Program project, ‘Total Diet Study Exposure’ (TDS-Exposure), aimed at standardising methods for food sampling, analyses, exposure assessment calculations and modelling, priority foods, and selection of chemical contaminants. A stepwise approach following the knowledge translation (KT) model for concept analysis is proposed to set up a general protocol for the collection of food products in a TDS in terms of steps (characterisation of the food list, development of the food-shopping list, food products collection) and pillars (background documentation, procedures, and tools). A simple model for structuring the information in a way to support the implementation of the process, by presenting relevant datasets, forms to store inherent information, and folders to record the results is also proposed. Reproducibility of the process and possibility to exploit the gathered information are two main features of such a system for future applications.     

Occurrence of toluene in Canadian total diet foods and its significance to overall human exposure

Levels of most VOCs in foods are usually low because of their volatility, and human exposure to VOCs is expected to be mainly via inhalation of ambient and indoor air. However, dietary exposures to VOCs can be significant to overall exposures if elevated concentrations of VOCs are present in foods consumed in high amounts and/or on a regular basis, and this was demonstrated in this study with the occurrence data of toluene from the recent 2014 Canadian Total Diet Study (TDS). Concentrations of toluene in the composite samples of most food types from the 2014 TDS are low and similar to the results from the previous 2007 TDS with some exceptions, such as beef steak (670 ng/g (2014 TDS) vs. 14 ng/g (2007 TDS)), poultry, chicken and turkey (307 ng/g (2014 TDS) vs. 8.8 ng/g (2007 TDS)). Toluene concentrations in most of the grain-based and fast food composite samples from the 2014 TDS are considerably higher than those from the 2007 TDS, with the highest level of 4655 ng/g found in the composite sample of crackers from the 2014 TDS (compared to 18 ng/g from 2007 TDS). Dietary exposure estimates for toluene based on the occurrence results from the 2014 TDS show that for most of the age groups, grain-based foods are the primary source, accounting for an average of 77.5% of the overall toluene intake from the diet. The highest dietary exposures to toluene were observed for the adult age groups, with estimated average exposures ranging from 177.4 to 184.5 µg/d. Dietary exposure estimates to toluene are well below oral doses associated with toxicological effects and also below the maximum estimated intake (819 µg/d) from air inhalation for adult group (20 – 70 years) based on the results from CEPA (Canadian Environmental Protection Act) assessment in 1992.     

中国总膳食研究三十年之演变

总膳食研究是世界卫生组织极力推荐成员国评估某个国家和地区在不同人群组对于膳食中化学危害物暴露量和营养素摄入量的最经济、有效、可靠的方法。中共中央和国务院于2019年5月9日发布《关于深化改革加强食品安全工作的意见》将开展总膳食研究作为实施风险评估和标准制定专项行动的基础性工作,来完善风险评估基础数据库。本文从中国总膳食研究的意义、启动、发展与定型的历史演变过程解读这30年的发展历程,并对其在食品安全暴露科学中的作用进行述评。     

Assessment of infant exposure to food chemicals: the French Total Diet Study design

As part of the previous French Total Diet Studies (TDS) focusing on exposure to food chemicals in the population aged 3 years and older, the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) launched a specific TDS on infants to complete its overall chemical food safety programme for the general population. More than 500 chemical substances were analysed in food products consumed by children under 3 years old, including nutrients, several endocrine disruptors resulting from human activities (polychlorinated biphenyls, dioxins and furans, brominated flame retardants, perfluoroalkyl acids, pesticide residues, etc.) or migrating from food contact materials such as bisphenol A or phthalates, but also natural substances such as mycotoxins, phytoestrogens and steroids. To obtain a representative and general view of infant food consumption, food items were selected based on results of a national consumption survey conducted specifically on this population. Moreover, a specific study on food was conducted on 429 households to determine which home-cooking practices are employed to prepare food consumed by infants. Overall, the targeted chemical substances were analysed in more than 450 food samples, representing the purchase and home-cooking practices of over 5500 food products. Foods included common foods such as vegetables, fruit or cakes as well as specific infant foods such as infant formula or jarred baby food. The sampling plan covered over 80% of the total diet. Specificities in infant food consumption and habits were therefore considered to define this first infant TDS. This study, conducted on a large scale and focusing on a particularly sensitive population, will provide accurate information on the dietary exposure of children under 3 years to food chemicals, especially endocrine disruptors, and will be particularly useful for risk assessment analysis under the remit of ANSES’ expert committees.     

Dietary exposure estimates of isoflavones from the 1998 UK Total Diet Study.

The phyto-oestrogen contents of the 1998 UK Total Diet Study (TDS) food group composites were determined. Each TDS set consisted of composite samples, one for each of the 20 designated food groups. These composites then represented the average consumption of all the individual food elements in each group, processed into the form in which they were consumed. In the TDS, individual composites of the bread, processed meat and fish food groups contained >5 mg kg(-1) of the individual isoflavones (daidzein, genistein and glycitein). Individual composites from the groups, miscellaneous cereals, other vegetables, fruit products and nuts contained >1 mg kg(-1). After weighting for average consumption of food from each TDS food group, an estimated daily intake of 3 mg day(-1) of combined isoflavone aglycones was obtained from the TDS sample collection model for the average (adult) consumer. The UK dietary intake of phyto-oestrogens is higher than previously estimated due in part to the use of soya in processed foods.     

Core food model of the Taiwan food supply for total diet study

ABSTRACT

Following the core food (CF) models of the USA and France reported in the 2000s, this study presents the first oriental CF model, for total diet studies in Taiwan. First, we combined the four latest national dietary recall surveys from 2005 to 2012, data sets from the Nutrition and Health Survey in Taiwan (NAHSIT) covering all ages (1 to 65+ years old). In total, 3,098 NAHSIT food codes from 349,497 records of responses from 7,580 individuals were aggregated within a three-tiered scheme into 237 CFs in 54 subcategories and 16 categories. As with Western foods, Taiwanese foods were mainly aggregated by food type and major ingredient, processing method, cooking method or serving habit. In addition, we propose several categories typical to Taiwanese foods: (1) processed foods (e.g. rice paste, rice noodle, bean curd); (2) mixed foods (e.g. tomato fried with egg, Guangdong porridge) and stuffed staple foods (e.g. rice cake, zongzi); (3) Chinese Dim Sum (e.g. dumpling, salted bun); and (4) animal offal (e.g. pig liver, chicken kidney) and by-products (e.g. chicken head, pig foot). Systematic nomenclature and coding methods are also proposed. A computerised web model was developed using a graphical user interface (GUI) for automatic CF aggregation and inquiry of various consumption estimates according to the residing area, age group, and gender of consumers. Point estimates of weighted means were calculated for consumption rates (CR) based on the whole group (WG) or consumers only (CO). The CR and body weight (BW) of each individual were matched to calculate mean intake per unit body weight (g/kg bw/day). A general sample design procedure with the CF model is suggested for a total diet study (TDS) on target hazards. Strategies are also discussed for improving the quality of food matching in sample designs.     

Core foods of the US food supply

The core food dietary intake/exposure model may be used to assess the average intake of nutrients, contaminants and other food components by a population group and various subgroups of the population. The core food model is a mechanism that allows for the selection of the most important foods in a population's food supply so that these foods can be obtained and analysed in the laboratory. The core foods for a population change over time as food consumption patterns are altered by changes in the food supply and/or changes in the demographics of the population. Core foods of the US diet were selected using food consumption data from the 1994-96 US Department of Agriculture (USDA) Continuing Survey of the Food Intake of Individuals (CSFII). The 304 core foods were identified by placing the 5722 foods consumed by survey participants into about 300 groups. The groupings were based on food type, food use and similarity of nutrient composition. The foods within each grouping were ranked in terms of frequency of use and weight of intake, and one food item within each group was selected to become a core food and represent its group. In the model, each core food assumes the full dietary intake (by weight) for all the foods in its group. Daily mean intakes of the 304 selected core foods are presented for women and men of 19-30 years of age. If the food components of interest to investigators using this model are found in selected foods or food types, then only these foods need be analysed. The list of 304 core foods may be shortened by further aggregation to match the needs of different investigators. For example, limited data on food composition may warrant use of a shorter core food list. A shortened food list with average daily intakes of 78 core foods for women and men of 19-30 years of age is provided as an example.     

UK dietary exposure to PCDD/Fs,PCBs, PBDD/Fs,PBBs and PBDEs: comparison of results from 24-h duplicate diets and total diet studies

ABSTRACT

Chemicals in food are monitored to check for compliance with regulatory limits and to evaluate trends in dietary exposures, among other reasons. This study compared two different methods for estimating human dietary exposure to lipophilic persistent organic pollutants (POPs) during 2011/12: (1) the 2012 Total Diet Study (TDS) conducted by the UK Food Standards Agency (FSA) and (2) a 24-h duplicate diet (DD) study of 20 adults from the North East of England. The equivalence of the two approaches was assessed; anything less than an order of magnitude could be considered reasonable and within three-fold (equivalent to 0.5 log) as good. Adult dietary exposure estimates derived from the DD study for both average and high-level (97.5th percentile) consumers compared well with those from the TDS. Estimates from the DD study when compared with those from the TDS were within 10% for P97.5 for total PCDD/F/PCB with divergence increasing to a factor of 3.4 for average BDE-209. Most estimates derived from the TDS were slightly higher than those derived from the DD. Comparison with earlier UK TDS data over the last 30 years or so confirmed a gradual decline in levels of PCDD/F/PCBs in food. Such comparisons also indicated peaks in dietary exposure to ∑PBDE (excluding BDE-209) between 2000 and 2005. Exposure estimates for all measured compounds using both TDS and DD data were found to be within recommended tolerable daily intakes where available or within acceptable margins of exposure.     

The Beneficial Use of Cereal and Cereal Components in Probiotic Foods

Cereals and cereal components can be used as fermentation substrates for probiotic organisms imparting prebiotic effects. Consumer interest in healthy functional foods has resulted in the need for food products with versatile health-benefiting properties. The conventional choice for probiotic food applications has been dairy-based products, but whole grain-based probiotic functional foods have debuted in Japan and Europe. In the US, pro- and prebiotics are mainly marketed as dietary supplements, but are moving towards inclusion in the diet as mainstream foods. Cereal constituents, such as wheat bran-based ingredients fermented with probiotics, would enhance consumer health with the benefits of probiotics, bran fiber, and healthful bioactive components.     

Proceedings of the workshop on food-consumption surveys in developing countries: general approaches to estimation of dietary exposure to contaminants

The initial steps in estimating dietary exposure to contaminants include gathering the necessary expertise, clarifying the intent and purpose of the work, selecting a dietary exposure model, and gathering available pertinent information. Expertise is generally needed in chemistry, agriculture, toxicology, statistics, nutritional epidemiology, and computer software development. The goal might be to determine the average exposure of a population to contaminants, to identify demographic groups within a population that are especially vulnerable to a contaminant, to evaluate the regulation of agricultural and food-manufacturing practices, or to determine compliance with standards for local and/or imported foods. Examples of dietary exposure models include the core food model, directed core food model, large database model, raw agricultural commodity (RAC) model, regional diet model, duplicate diet model, and total diet composite model. Each model has advantages and disadvantages and different costs and resource requirements. Consideration of the sources and flow of selected contaminants though the food supply may help identify the best exposure model to use. Pertinent information that may already be available includes analytical data on contaminants in foods or commodities, government regulations pertaining to the levels of contaminants in foods, food-consumption data, data on the average body weights of age-gender groups (to express exposure on a body weight basis), and biochemical measures of contaminants or their residues/metabolites. Collecting available information helps to clearly define what critical information is missing so that the planned research can be most effective. Careful documentation of decisions and assumptions allows for recalculating exposure estimates with the same model using different decisions and assumptions; documentation also allows others to understand what was done and how to use the resulting intake estimates properly. Clearly identifying the limitations of the exposure model may provide justification for additional resources to further refine and improve the model.     

Do street food vendors sell a sufficient variety of foods for a healthful diet? The case of Nairobi

This study examined whether street food vendors sell a sufficient variety of foods for a healthful diet. It was hypothesized that vendors sold only low-cost food groups to enable the buyer to afford the food while the vendor also made a profit. A structured questionnaire was administered to 580 vendors in three selected locations. Data included product names, ingredients, methods of preparation, and the sex of the vendor. A little more than half of the vendors (53%) sold food of only one group; 44% sold cereals. Overall, 36% of vendors, mostly men, sold only carbohydrate products. The percentage of vendors selling foods of more than one group was higher in the working area (53%) than in the slum area (43%, p < .05), and it was higher in both of these areas taken together than in the lower-middle income area (21%, p < .001). Micronutrient and mixed-nutrient products were associated with female vendors. Although a slight majority of all street vendors sell foods of only one group, women vendors are capable of supplying a sufficient variety of food groups that consumers can afford. It appears that consumer purchasing power dictates the food groups provided by vendors, especially cereal-based-foods. A policy on micronutrient fortification of cereal flours and fats used in popular street food preparation needs to be considered. This could be coupled with consumer and vendor education programs focusing on the importance of healthful diets.     

Sampling design by the core-food approach for the Taiwan total diet study on veterinary drugs

ABSTRACT

The core-food (CF) approach, first adopted in the United States in the 1980s, has been widely used by many countries to assess the exposure to dietary hazards at a population level. However, the reliability of exposure estimates (C × CR) depends critically on sampling methods designed for the detected chemical concentrations (C) of each CF to match with the corresponding consumption rate (CR) estimated from the surveyed intake data. In order to reduce the uncertainty of food matching, this study presents a sampling design scheme, namely the subsample method, for the 2016 Taiwan total diet study (TDS) on veterinary drugs. We first combined the four sets of national dietary recall data that covered the entire age strata (1–65+ years), and aggregated them into 307 CFs by their similarity in nutritional values, manufacturing and cooking methods. The 40 CFs pertinent to veterinary drug residues were selected for this study, and 16 subsamples for each CF were designed by weighing their quantities in CR, product brands, manufacturing, processing and cooking methods. The calculated food matching rates of each CF from this study were 84.3–97.3%, which were higher than those obtained from many previous studies using the representative food (RF) method (53.1–57.8%). The subsample method not only considers the variety of food processing and cooking methods, but also it provides better food matching and reduces the uncertainty of exposure assessment.     

US Food and Drug Administration's Total Diet Study: intake of nutritional and toxic elements, 1991-96

The Food and Drug Administration (FDA) has conducted the Total Diet Study (TDS) annually since 1961. The TDS is designed to monitor the US food supply for levels of toxic chemical contaminants (pesticide residues, industrial chemicals and toxic elements) and nutritional elements. Foods are generally collected four times a year, once from each of four regions of the country. The foods are prepared table-ready before being analysed. From the results of the TDS, dietary intakes of these analytes are estimated for selected age- sex groups in the US population. This paper reports on the dietary intake of 10 nutritional and four toxic elements based on measurements made in foods collected in the TDS between 1991 and late 1996. Average daily intakes were estimated for 14 age-sex groups in the US population, as well as the contribution of specific food groups to total intakes. For most nutritional elements, teenage boys and adult males had the highest daily intakes. Intakes by infants were below the intake references for seven of 10 nutritional elements, and young girls and women had inadequate intakes of at least half the nutritional elements. Intakes by children between 2 and 10 years of age, teenage boys, and adult males met or exceeded the reference intakes for the majority of nutritional elements. Intakes by all population groups were well below the reference intakes for all toxic elements.