The 7dDD is a valuable tool for studying the association between diet and illness or healthy aging in the EPIC-Norfolk study. This data can be combined with the UK version of the FFQ and a paper-based version of the 24hDR. A copy of the 7dDD is available for downloaded.
The EPIC-Norfolk 7dDD was based on the diary used in the British Birth Cohort and follows a similar structure. 7dDDs form the primary dietary assessment used in EPIC-Norfolk and the latest version was issued as A5, 50-page booklets. Participants recorded everything that they ate for seven consecutive days (covering weekdays and weekend days) describing amounts and how foods were prepared. The pages for each day have eight sections, seven meal slots for recording food and drinks taken from midnight to midnight, and a checklist and section for recording additional snacks and other information.
7dDD – instruction pages
The front pages of the 7dDD include suggestions for describing and quantifying food and drinks consumed. Participants are encouraged to include full information including how foods are cooked, the type of fat or oil used in preparation or frying, brand names of commercial products and details of recipes used. The amount an individual consumes of each food item or beverage is crucial information. Detailed instructions are included on how different foods may be usefully quantified, for example, colour photographs showing different portions sizes.
At the 1HC, the diary layout was explained to participants by a nurse and standardised instructions given on how to complete it. To help this process the participant was asked to recall the previous day’s intake from waking to going to bed, and the details written into the first day of the diary. The following six days were completed at home and diaries returned in a freepost envelope.
At further time-points, diaries were posted out or handed to participants at a health check, with reminders as to what information was needed to encourage adequate records.
Data processing using DINER and DINERMO
When the EPIC-Norfolk study began, there were no data entry and nutrient analysis systems suitable for a large-scale study with a long period of data collection. Systems available were unable to record sufficient detail, as they were based on the limited number of food types available within the available national food composition databases. The range of published portion sizes was also limited. A system was needed that would be robust enough to deal with the changes that occur within the food supply over time and also to investigate the many hypotheses of interest.
A series of programs and databases that constitute the Data Into Nutrients for Epidemiological Research (DINER) and DINERMO programs were developed at EPIC-Norfolk to convert 7dDD or 24hDR information into structured data for dietary analysis.
Extensive databases were developed and maintained to support DINER and DINERMO. All databases can be updated and extended as new data becomes available without the re-coding of food records.
DINER is the program used for entering the dietary data from the 7dDDs and 24hDRs.
Trained data enterers coded the data according to specified guidelines by selecting items from the extensive food list within DINER (nearly 11,000 items) and entering the associated portion size and any other information.
Each food item in the 7dDD or 24hDR is represented by one line of data in the final structure. A sandwich is entered as bread, spread and filling, a cup of tea is entered as black tea and milk (and sugar/sweetener where taken).
DINERMO consists of further programs and databases which check the entered data for completeness, the appropriateness of food choices and correct use of portion sizes. The underlying databases are checked (e.g. for portions, food densities or cooking losses) and new foods added where required.
Each food item in a diary is converted from the entered data into a weight of that food and the nutrients contained in that weight calculated. Nutrient intakes for each day are calculated and average daily nutrient intakes for each individual from all of the completed diary days.
The calculation program uses a nutrient database based on the 2200 foods in the UK food composition database (UKFCD). For new foods, nutrient data are derived by matching the known composition of the new food to proportions of up to four existing items in the UKFCD, to create the best possible nutritional equivalent. The design of DINER allows the range of nutrients processed to be extended.
The DINERMO data can also be used to calculate food intake. i.e. rather than calculating vitamin C intake, we may be interested in the weight of the sum of all fruits and vegetables combined.
For further information see the publications on DINER & DINERMO.