Measuring short-term dietary intake: development and testing of a 1-week food frequency questionnaire.

Measures typically used to assess short-term intake are 24-hour recalls or records of food intake. However, these methods require a large time commitment from both researchers and subjects. Our study sought to develop a more time-efficient method of assessing short-term intake by developing a 7-day food frequency questionnaire (7DFFQ). We modified Willett's 1-year food frequency questionnaire to assess intake for a 7-day period. Content validity has previously been exhibited in Willett's work. We assessed criterion validity by comparing the 7DFFQ with 24-hour recalls. Twenty-one female and 20 male college students were asked to recall their previous day's intake three times during a 1-week period. After the last recall, subjects completed a 7DFFQ covering the same week. Data were analyzed by comparing each recall and the mean of the three recalls with values obtained on the 7DFFQ. Analyses revealed high correlations between the mean of the three recalls and the 7DFFQ. Further analysis ranked subjects into quartiles for each nutrient on both measures. Most subjects changed either no quartiles or only one quartile for total energy and each nutrient. Test/retest reliability was assessed by administering the 7DFFQ to a group of women for two consecutive weeks and by administering the 7DFFQ to a group twice 3 hours apart. Pearson's r and intraclass correlations for the two administrations show moderately high reliability over the 1-week period and considerable improvement with the 3-hour administration. The 7DFFQ appears to meet several of the criteria for a measure of dietary intake.