Dietary history from the distant past: A methodological study

One of the major concerns regarding case-control studies of diet and cancer is that dietary measures based on current habits may not accurately reflect dietary intake from the time period of cancer initiation and early promotion in the more distant past. Thus, the extent to which current diet correlates with past diet and the reliability of retrospective estimates of past diet are important questions for researchers investigating dietary factors in cancer causation. For these reasons, we conducted this study of the reliability of dietary history as recalled from the distant past. Individuals (N = 175) who completed dietary interviews between the years 1957 and 1965 were reinterviewed in 1982. Subjects were asked to report the usual frequency of intake of selected food items, both at the time of their original interview in the 1957-1965 era as well as at the current time. Dietary histories as recalled from the distant past more closely agreed with those originally recorded than did current diets. The diets as recalled from the distant past appeared to be biased, however, by current dietary habits. The implications of these findings for diet and cancer research are discussed.