Objectives: To describe the use of dietary assessment methods in a cohort study.
Subjects: The Avon Longitudinal Study of Parents and Children (ALSPAC) based in Bristol, UK, a cohort of children born in 1991/1992 and their parents.
Methods and results: Data were collected about maternal and paternal diet, breastfeeding, weaning and childhood diet by both food frequency questionnaire (FFQ) and unweighed diet records (children only). Other questionnaires have covered socioeconomic background and eating behaviours. Nutrient and food group intakes were calculated from both FFQ and diet records. These were used singly and in combination to assess the contribution of diet to various growth and development outcomes in the children and in relation to socioeconomic position and other behaviours. Both methods provided important contributions to knowledge and have enhanced each other, allowing the development of the assessment instruments as experience in their use was gained. Statistical analysis methods such as the use of dietary patterns to summarize the diet were explored.
Conclusions: Longitudinal cohort studies are greatly enhanced if dietary assessment methods are built into their design. The use of more than one method of dietary assessment can increase the scientific usefulness of a study.