How is food composition data compiled?
A variety of methods are used to compile food composition data (FCD) at a national level by many countries, including:
- Chemical analysis of food samples
- Calculation of values using yield and nutrient retention factors
- ‘Borrowing’ values from one food composition database (FCDB) to another
- Adopting values from other sources, e.g. scientific literature for analysed values or food labels for branded foods
Chemical analysis of samples that are representative of the foods being consumed in a country is usually the preferred method for producing FCD. The food samples are carefully chosen according to a defined sampling plan. The food samples are collected, transported to an analytical laboratory and stored in an appropriate way. If necessary, further preparation and cooking takes place prior to the analysis using appropriate analytical methods.
Owing to limited resources, it is not feasible to determine these levels of every nutrient in every food. Compilers of FCDBs therefore use other approaches to determine the required nutrient values within a FCDB. For example, values for a raw food or dish can often be used, in conjunction with information on likely weight and nutrient changes due to cooking, to estimate values for a cooked food. This recipe calculation approach incorporates adjustments for weight change (or yield) on cooking and changes in the nutrient content on cooking (e.g. vitamin losses). Another approach commonly used by FCDB compilers is to ‘borrow’ or ‘adopt’ nutrient values that were originally compiled by another organisation. When using this approach, compilers will ensure that borrowed data are compatible with their own database.
Commonly used data sources for borrowed data are FCDBs from other countries or manufacturers’ data (e.g. from food labels). Before incorporating data from any of these sources into their FCDBs, compilers will evaluate the data in terms of both data quality and applicability of foods to the database. Information about the food, the nutrient values and their derivation will also be documented, so that compilers and users of the database can access these details.
The provision of high quality data in the FCDBs linked with EuroFIR is one of the most important goals of the network. Therefore, skilled and experienced technical experts are continuously working towards improving the content and quality of the data in their FCDBs. The data are thoroughly documented for best possible transparency, aggregated, validated and compiled following strict and standardised quality evaluation procedures before they can be published in the FCDBs and be made available for all data users. The provision of a quality index for each value will be one of the aims of the FCDBs in the future, increasing the usefulness of the data for all users.