Precision and estimated accuracy of two short-term food frequency questionnaires compared with recalls and records.

Two widely used food frequency questionnaires (Block FFQ, Willett FFQ) were modified to reflect intake over the past 7 days and compared to intake information gathered from diet records and 24-hr recalls covering the same 7-day period. The Block FFQ and the Willett FFQ were also gathered at the beginning of the assessment period to reflect the 7-day period of time before records and recalls were gathered. Fifty-six subjects were assigned to either recording diet for 3 days, recording diet for 6 days, or providing three 24-hr recalls. Results indicate similar levels of within-method test-retest reliabilities for 3-day RECORDS and 6-day RECORDS, and within the two Block FFQs and within the two Willett FFQs from each subject, while lower reliabilities were seen in 24-hr RECALLS. When the FFQs were compared to the 6-day RECORDS with between-method agreement coefficients, there was a moderate level of agreement, with most values between 0.5 and 0.8 for both FFQs. Significant differences between mean levels of nutrients estimated by the three methods indicated differences only in the estimates of carbohydrate and vitamin A. The use of FFQs to gather short-term intake information is discussed.