Reliability and validity of a food frequency checklist.

Test-retest of a food frequency checklist, which allowed for recall of food intakes during childhood and at the present time, proved that the checklist was a reliable measure of change of individuals' food consumption. Validity of the method was established by comparing mean intakes of specific food groups during the respondents' two life periods with mean intakes of their age cohorts in the 1965-66 and 1977-78 USDA Nationwide Food Consumption Surveys.