Retrospective assessment of dietary intake.

In studying the role of diet in chronic disease etiology, measurement of past intake may be of more relevance than measurement of that existing either at the time of or just preceding the clinical onset of disease. In 1983, in metropolitan Adelaide, South Australia, estimates of current and previous dietary intake were obtained, by use of a semiquantitative food frequency questionnaire, from 70 individuals (37 male, 33 female), from each of whom an estimate of intake, using the same questionnaire, had been obtained three years earlier. Over this three-year period, median nutrient and energy intake had declined. In relative, if not absolute terms, individuals were able to make satisfactory retrospective estimates of original nutrient and energy intake; however, their retrospective estimates appeared to have been influenced by their current intakes. Nevertheless, the strong correlations observed between retrospective and original estimates of intake suggest that the semiquantitative food frequency method of retrospective dietary assessment allows a reliable relative ranking of individuals by nutrient intake within a population.