[Assessment of dietary intake at the population level through individual questionnaires: methodological shadows and lights].

The development of the modern methodology necessary to accurately characterize dietary intake in individuals and population only dates back two decades, when nutritional epidemiology first emerged. The reason for the recentness of this discipline lies in the fact that dietary assessment at the population level presents complex challenges which are only being overcome as we investigate and improve the available methodological instruments. In this paper, alternative methods to estimate food and nutritional intake are reviewed. Following a succinct description of direct and indirect methods to evaluate dietary consumption, including a brief reference to biomarkers and mixed techniques such as "total diet" studies, the article focuses on direct methods of quantifying dietary intake through questionnaires. The basis, advantages, and limitations of alternative options are considered, and subsequently the article summarizes the development of new survey designs and analytical/statistical techniques which aim to optimize the available methodology. The article finally concludes by affirming that the approximations indicated by the complementary introduction of biomarkers, together with the optimized use of combined methods with questionnaires, are potentially the most precise and trustworthy estimations of dietary intake at the population level. In light of both the advances achieved and the pending challenges, it is clear that there is a strong necessity to foster research which will lead to improvement in the methodology in this field.