Comparability of dietary patterns assessed by multiple dietary assessment methods: results from the 1946 British Birth Cohort

Objective: The aim of this study is to evaluate the consistency of dietary patterns assessed through the use of a dietary recall and a 5-day food diary. Design: Participants (n=2265) of a longitudinal study of health and development completed 48-h dietary recall at interview, followed by a 5-day food diary and with the 24 h immediately preceding the interview analysed separately as a 24-h recall. Mean intakes of foods and nutrients were calculated and dietary patterns were assessed using exploratory factor analysis, using the method of principal components. Paired t-tests and correlation coefficients were used to compare the three dietary assessment methods. Results: Five distinct dietary patterns were identified using the food diary and the 48-h recall but were less consistent on the 24-h recall. Correlations between factor scores on the 48-h recall and the food diary (r=0.13-0.67) were higher than those between the 24-h recall and food diary (r=-0.01-0.59). The recall methods were effective at ranking subjects according to food and nutrient intakes, with the 48-h recall and food diary showing higher correlations in both males and females. Conclusions: This study indicates that a 48-h recall effectively characterises dietary patterns in British adults when compared to a food diary and ranks participants appropriately with respect to most nutrients and foods and is superior to a single 24-h recall. These results have implications for longitudinal studies where maximising response rates to repeat dietary assessment tools is essential.