A 24HR was sent out to all potential EPIC participants with the invitation to join the study. This short questionnaire asked for a record of all food and drink, including snacks, taken over the previous day.
Over 30,000 participants completed 24HRs which they returned by post. Most of these people participated in a first health check and went on to complete a 7DD. The 24HR is the only dietary record for those who did not attend a health check. A second 24HR was sent out with the invitations to the second health check three years later.
These questionnaires were coded using DINER, see the data processing section.