24-Hour Dietary Recall

A key component of the Calibration Sub-Study
is the 24-hour dietary recall. Participants in the study (approximately 1000) were called and asked what foods and supplements they had consumed the day before.

Calls

Attempts were made to obtain a total of 6 recalls for each participant of the sub-study. The six recalls were grouped into two sets, each consisting of a Saturday, Sunday, and weekday recall. The each subject's sets of recalls was generally obtained separated by several months to capture seasonal differences. The recall interviews were recorded for later transcription.

Transcription and Recipe Creation

The recorded recall interviews were transcribed into the NDSR system, and recipes were created for the reported foods consumed.

Nutrient Consumption

Nutrients

The nutrients available for the 24-hour recalls are the same ones available from the baseline questionnaire
.

Calculation

From the 6 recalls, two synthetic weeks were constructed which could then be used to produce an average daily intake. The synthetic weeks were constructed as follows:

* Synthetic Week - sum of:
* Sunday recall intake
* Weekday recall intake - multiplied by 5
* Saturday recall intake

By dividing the synthetic weekly intake by 7, an average daily intake for the week is produced.

The average daily intake for the two synthetic weeks can then be averaged, or used separately in establishing within-subject variation.