Dietary assessment and validity: To measure what is meant to measure

Abstract

Nutritional assessment is the interpretation of information obtained from dietary, biochemical, anthropometric and clinical studies. In individuals, qualitative or quantitative food consumption data may be collected by food frequency questionnaires or interviews (retrospective methods), by use of food records (prospective methods); weighed food record, estimated food record or menu record, or by observations. Nutrient values derived from food composition data or direct chemical analysis represent the maximum available to the body and not the amount actually absorbed and utilized. The design of the study is crucial and the methods for carrying it out are aimed at minimizing bias to improve internal and external validity. This paper will focus on factors of importance to improve the internal validity of dietary assessment studies; selection of method; data collection, assessment of nutrient intakes from food consumption data and evaluation of data.