The Dietary Assessment Team focuses on the innovation and advancement of methodology to assess dietary intake through the development of novel techniques for dietary assessment, enhancements to food composition databases and provision of expert guidance. We specialise in the use of diet diaries for use in national surveys and cohorts and dietary intervention studies. This work underpins many of our research projects and is a vital source of evidence for broader diet and population health policy.
Food Composition Databases
When conducting dietary assessment, there is a need for an up to date food composition database to translate the record of foods consumed into intake of nutrients. The basis for the nutrient content of foods in the UK derives from McCance and Widdowson’s “The Composition of Foods” which was first published in the 1940′s and revised 5 times since. The Composition of Foods has an extensive list of foods, but it cannot keep up-to-date with all the products now available in the supermarket. Our food composition experts are continually updating our database to incorporate many additional foods via recipe calculations and the use of manufacturers’ ingredient information. Current collaborative studies at HNR on infants and young children, and children of different ethnic backgrounds, require specific additions to the database to include foods eaten by these groups.
Data are available for macro and micronutrients and food constituents are added as required by new research hypotheses on the aetiology and prevention of cardiovascular, bone and other degenerative diseases. Recent and ongoing additions include phytate, vitamin K1, silicon, and haem and non-haem iron. We are also disaggregating many mixed dishes to be able to calculate consumption of meat and fruit and vegetables accurately, which is important for finding out if dietary recommendations, such as 5-a-day, are being met.
Gambian food composition database
MRC Nutrition Units in Cambridge have been working in the Gambia for over 30 years. The collection of dietary records continues to be a valuable part of the assessment of health and disease in Africa as it does elsewhere.
Over many years research workers have collected a large quantity of dietary records in the form of weighed intakes. Samples of cooked foods were collected and returned to Cambridge for analysis. Together with computations based on information about recipes gathered in the field, we now have an extensive database of composition of Gambian foods which became available in book format in 2007: “Food Composition Table for use in The Gambia” (2005), C.J. Prynne and A.A. Paul.
Dietary assessment methodologies
HNR is continually advancing dietary assessment methods in order to obtain the most accurate information as possible from study participants. Our most common dietary assessment methodology is the estimated (unweighed) diet diary, where subject participants record food and drinks consumed over a period of several days. In recent years, we have made efforts to capture the social and cultural factors influencing food quality and quantity, and by developing food diaries where information about the socio-ecological environment of the foods consumed are recorded.
For example, space has now been allocated for subjects to write where the food was eaten and others present at the time of eating, whether the television was on and if the food was consumed while sitting at a table. Thus we can identify food eaten at a family meal around a table or food eaten alone while watching television. These factors can then be related to food and nutrient intakes and diet quality and the influences of socio-economic status, age, sex and region explored.
The adult food diary used for many years at HNR has been adapted for toddlers, primary school children and teenagers. The children’s diaries are in a large format, allowing more space for children to write. The diary for toddlers is for completion by parents and has separate sections for solid food and for milk and other drinks. In order to make identification of food products easier, particularly with the abundance of ready made mixed dishes (“ready meals”) in the marketplace, study participants are encouraged to collect food labels and wrappers from the foods they have consumed and recorded in the diary. These are invaluable for determining the ingredients of the product, so improving the accuracy of the record.
Many individuals, particularly children, find it hard to describe the food they have eaten, either in terms of content or portion size. New technologies are emerging in the field to enable photographs to be taken of the foods consumed, and in some cases, handheld devices to record information either verbally or in text. HNR has undertaken a pilot study to investigate the feasibility and usefulness of giving children digital cameras alongside their diaries to take photographs of the food items consumed. This pilot was carried out in collaboration with colleagues at St George’s Hospital, London, undertaking the CHASE study. This pilot study has shown that digital photography can enhance the accuracy of the diet record by providing more detail on types and amounts of foods eaten than the diary alone.