Validity of a food frequency questionnaire for the determination of individual food intake.

The validity of a food frequency questionnaire for dietary assessment was tested with 31 college students living and dining in a dormitory. A food frequency questionnaire was mailed to participants requesting them to estimate their usual intake of specific food items. Actual food consumption was determined at each meal with self-report forms. These forms required participants to indicate foods chosen at that meal. To test the validity of the frequency questionnaire, regression equations were calculated for each individual using the frequency questionnaire data as the independent variable (X) and actual intake data as the dependent variable (Y). Eighty-four percent of the r values were greater than 0.50 and 55% were greater than 0.71. All were significant at the 0.002 level or below. As an alternative test of validity, the percentage of over- and underestimation of each food group was also assessed. Foods which are often major components of a meal (eg, flesh foods) were estimated with greater accuracy than those foods which could be considered accessory (eg, nuts or seeds). While it appears that a large percentage of individuals could accurately estimate their intake with this technique, some individuals were unsuccessful in doing so. Further research is needed to identify individual characteristics which may predict success with this technique.