The relative validity of a retrospective estimate of food consumption based on a current dietary history and a food frequency list.

The relative validity of information and food consumption in the distant past was assessed by combining a dietary history (referring to the recent past) with a food frequency list (monitoring major changes over the past 12-14 years). This approach was evaluated in a study of two groups of apparently healthy elderly people (mean age 80 years) who had participated in a food consumption study 12-14 years before the start of the present study. One group consisted of 18 harbor employees who retired subsequent to the initial assessment of food intake. On the average, each member of this group had reduced his food consumption by about 1,000 kcal. The other group consisted of 46 elderly men and women who had retired before their food consumption was measured initially. This group had not markedly changed their food intake. The results showed that both groups overestimated changes in their food intake and that the systematic overestimation and random error were similar for both groups. If the men in both groups were combined to form one group, a valid ranking of subjects in small and large consumers of energy and most of the selected nutrients was possible. However, current food intake influenced the accuracy of the measurement of past food intake.