Abstract
Dietary assessment is an important component of longitudinal studies, allowing examination of the role of nutritional factors on health and societal outcomes. Dietary intake can be assessed by a number of methods, varying in respondent and interviewer burden, cost, and detail of type and quantity, as well as frequency of foods consumed. Many longitudinal studies utilise Food Frequency Questionnaires (FFQs) because of ease of administration and low cost, but these lack food detail, rely on good memory and have been questioned in terms of their capability to show diet-disease relationships. Estimated diet diaries are growing in popularity because of lower respondent burden than weighed records yet providing equally valid information, with more detail than FFQs. Costs of coding and translation to nutrients can be built into study budgets; estimated diaries should be considered for longitudinal studies to enable the role of diet in health and lifestyle to be accurately investigated.